/src/postgres/src/backend/executor/nodeWindowAgg.c

Source (jump to first uncovered line)
/*-------------------------------------------------------------------------
 *
 * nodeWindowAgg.c
 *    routines to handle WindowAgg nodes.
 *
 * A WindowAgg node evaluates "window functions" across suitable partitions
 * of the input tuple set.  Any one WindowAgg works for just a single window
 * specification, though it can evaluate multiple window functions sharing
 * identical window specifications.  The input tuples are required to be
 * delivered in sorted order, with the PARTITION BY columns (if any) as
 * major sort keys and the ORDER BY columns (if any) as minor sort keys.
 * (The planner generates a stack of WindowAggs with intervening Sort nodes
 * as needed, if a query involves more than one window specification.)
 *
 * Since window functions can require access to any or all of the rows in
 * the current partition, we accumulate rows of the partition into a
 * tuplestore.  The window functions are called using the WindowObject API
 * so that they can access those rows as needed.
 *
 * We also support using plain aggregate functions as window functions.
 * For these, the regular Agg-node environment is emulated for each partition.
 * As required by the SQL spec, the output represents the value of the
 * aggregate function over all rows in the current row's window frame.
 *
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/backend/executor/nodeWindowAgg.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/htup_details.h"
#include "catalog/objectaccess.h"
#include "catalog/pg_aggregate.h"
#include "catalog/pg_proc.h"
#include "executor/executor.h"
#include "executor/nodeWindowAgg.h"
#include "miscadmin.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/optimizer.h"
#include "parser/parse_agg.h"
#include "parser/parse_coerce.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/datum.h"
#include "utils/expandeddatum.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/regproc.h"
#include "utils/syscache.h"
#include "windowapi.h"

/*
 * All the window function APIs are called with this object, which is passed
 * to window functions as fcinfo->context.
 */
typedef struct WindowObjectData
{
  NodeTag   type;
  WindowAggState *winstate; /* parent WindowAggState */
  List     *argstates;    /* ExprState trees for fn's arguments */
  void     *localmem;   /* WinGetPartitionLocalMemory's chunk */
  int     markptr;    /* tuplestore mark pointer for this fn */
  int     readptr;    /* tuplestore read pointer for this fn */
  int64   markpos;    /* row that markptr is positioned on */
  int64   seekpos;    /* row that readptr is positioned on */
} WindowObjectData;

/*
 * We have one WindowStatePerFunc struct for each window function and
 * window aggregate handled by this node.
 */
typedef struct WindowStatePerFuncData
{
  /* Links to WindowFunc expr and state nodes this working state is for */
  WindowFuncExprState *wfuncstate;
  WindowFunc *wfunc;

  int     numArguments; /* number of arguments */

  FmgrInfo  flinfo;     /* fmgr lookup data for window function */

  Oid     winCollation; /* collation derived for window function */

  /*
   * We need the len and byval info for the result of each function in order
   * to know how to copy/delete values.
   */
  int16   resulttypeLen;
  bool    resulttypeByVal;

  bool    plain_agg;    /* is it just a plain aggregate function? */
  int     aggno;      /* if so, index of its WindowStatePerAggData */

  WindowObject winobj;    /* object used in window function API */
}     WindowStatePerFuncData;

/*
 * For plain aggregate window functions, we also have one of these.
 */
typedef struct WindowStatePerAggData
{
  /* Oids of transition functions */
  Oid     transfn_oid;
  Oid     invtransfn_oid; /* may be InvalidOid */
  Oid     finalfn_oid;  /* may be InvalidOid */

  /*
   * fmgr lookup data for transition functions --- only valid when
   * corresponding oid is not InvalidOid.  Note in particular that fn_strict
   * flags are kept here.
   */
  FmgrInfo  transfn;
  FmgrInfo  invtransfn;
  FmgrInfo  finalfn;

  int     numFinalArgs; /* number of arguments to pass to finalfn */

  /*
   * initial value from pg_aggregate entry
   */
  Datum   initValue;
  bool    initValueIsNull;

  /*
   * cached value for current frame boundaries
   */
  Datum   resultValue;
  bool    resultValueIsNull;

  /*
   * We need the len and byval info for the agg's input, result, and
   * transition data types in order to know how to copy/delete values.
   */
  int16   inputtypeLen,
        resulttypeLen,
        transtypeLen;
  bool    inputtypeByVal,
        resulttypeByVal,
        transtypeByVal;

  int     wfuncno;    /* index of associated WindowStatePerFuncData */

  /* Context holding transition value and possibly other subsidiary data */
  MemoryContext aggcontext; /* may be private, or winstate->aggcontext */

  /* Current transition value */
  Datum   transValue;   /* current transition value */
  bool    transValueIsNull;

  int64   transValueCount;  /* number of currently-aggregated rows */

  /* Data local to eval_windowaggregates() */
  bool    restart;    /* need to restart this agg in this cycle? */
} WindowStatePerAggData;

static void initialize_windowaggregate(WindowAggState *winstate,
                     WindowStatePerFunc perfuncstate,
                     WindowStatePerAgg peraggstate);
static void advance_windowaggregate(WindowAggState *winstate,
                  WindowStatePerFunc perfuncstate,
                  WindowStatePerAgg peraggstate);
static bool advance_windowaggregate_base(WindowAggState *winstate,
                     WindowStatePerFunc perfuncstate,
                     WindowStatePerAgg peraggstate);
static void finalize_windowaggregate(WindowAggState *winstate,
                   WindowStatePerFunc perfuncstate,
                   WindowStatePerAgg peraggstate,
                   Datum *result, bool *isnull);

static void eval_windowaggregates(WindowAggState *winstate);
static void eval_windowfunction(WindowAggState *winstate,
                WindowStatePerFunc perfuncstate,
                Datum *result, bool *isnull);

static void begin_partition(WindowAggState *winstate);
static void spool_tuples(WindowAggState *winstate, int64 pos);
static void release_partition(WindowAggState *winstate);

static int  row_is_in_frame(WindowAggState *winstate, int64 pos,
              TupleTableSlot *slot);
static void update_frameheadpos(WindowAggState *winstate);
static void update_frametailpos(WindowAggState *winstate);
static void update_grouptailpos(WindowAggState *winstate);

static WindowStatePerAggData *initialize_peragg(WindowAggState *winstate,
                        WindowFunc *wfunc,
                        WindowStatePerAgg peraggstate);
static Datum GetAggInitVal(Datum textInitVal, Oid transtype);

static bool are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
            TupleTableSlot *slot2);
static bool window_gettupleslot(WindowObject winobj, int64 pos,
                TupleTableSlot *slot);


/*
 * initialize_windowaggregate
 * parallel to initialize_aggregates in nodeAgg.c
 */
static void
initialize_windowaggregate(WindowAggState *winstate,
               WindowStatePerFunc perfuncstate,
               WindowStatePerAgg peraggstate)
{
  MemoryContext oldContext;

  /*
   * If we're using a private aggcontext, we may reset it here.  But if the
   * context is shared, we don't know which other aggregates may still need
   * it, so we must leave it to the caller to reset at an appropriate time.
   */
  if (peraggstate->aggcontext != winstate->aggcontext)
    MemoryContextReset(peraggstate->aggcontext);

  if (peraggstate->initValueIsNull)
    peraggstate->transValue = peraggstate->initValue;
  else
  {
    oldContext = MemoryContextSwitchTo(peraggstate->aggcontext);
    peraggstate->transValue = datumCopy(peraggstate->initValue,
                      peraggstate->transtypeByVal,
                      peraggstate->transtypeLen);
    MemoryContextSwitchTo(oldContext);
  }
  peraggstate->transValueIsNull = peraggstate->initValueIsNull;
  peraggstate->transValueCount = 0;
  peraggstate->resultValue = (Datum) 0;
  peraggstate->resultValueIsNull = true;
}

/*
 * advance_windowaggregate
 * parallel to advance_aggregates in nodeAgg.c
 */
static void
advance_windowaggregate(WindowAggState *winstate,
            WindowStatePerFunc perfuncstate,
            WindowStatePerAgg peraggstate)
{
  LOCAL_FCINFO(fcinfo, FUNC_MAX_ARGS);
  WindowFuncExprState *wfuncstate = perfuncstate->wfuncstate;
  int     numArguments = perfuncstate->numArguments;
  Datum   newVal;
  ListCell   *arg;
  int     i;
  MemoryContext oldContext;
  ExprContext *econtext = winstate->tmpcontext;
  ExprState  *filter = wfuncstate->aggfilter;

  oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);

  /* Skip anything FILTERed out */
  if (filter)
  {
    bool    isnull;
    Datum   res = ExecEvalExpr(filter, econtext, &isnull);

    if (isnull || !DatumGetBool(res))
    {
      MemoryContextSwitchTo(oldContext);
      return;
    }
  }

  /* We start from 1, since the 0th arg will be the transition value */
  i = 1;
  foreach(arg, wfuncstate->args)
  {
    ExprState  *argstate = (ExprState *) lfirst(arg);

    fcinfo->args[i].value = ExecEvalExpr(argstate, econtext,
                       &fcinfo->args[i].isnull);
    i++;
  }

  if (peraggstate->transfn.fn_strict)
  {
    /*
     * For a strict transfn, nothing happens when there's a NULL input; we
     * just keep the prior transValue.  Note transValueCount doesn't
     * change either.
     */
    for (i = 1; i <= numArguments; i++)
    {
      if (fcinfo->args[i].isnull)
      {
        MemoryContextSwitchTo(oldContext);
        return;
      }
    }

    /*
     * For strict transition functions with initial value NULL we use the
     * first non-NULL input as the initial state.  (We already checked
     * that the agg's input type is binary-compatible with its transtype,
     * so straight copy here is OK.)
     *
     * We must copy the datum into aggcontext if it is pass-by-ref.  We do
     * not need to pfree the old transValue, since it's NULL.
     */
    if (peraggstate->transValueCount == 0 && peraggstate->transValueIsNull)
    {
      MemoryContextSwitchTo(peraggstate->aggcontext);
      peraggstate->transValue = datumCopy(fcinfo->args[1].value,
                        peraggstate->transtypeByVal,
                        peraggstate->transtypeLen);
      peraggstate->transValueIsNull = false;
      peraggstate->transValueCount = 1;
      MemoryContextSwitchTo(oldContext);
      return;
    }

    if (peraggstate->transValueIsNull)
    {
      /*
       * Don't call a strict function with NULL inputs.  Note it is
       * possible to get here despite the above tests, if the transfn is
       * strict *and* returned a NULL on a prior cycle.  If that happens
       * we will propagate the NULL all the way to the end.  That can
       * only happen if there's no inverse transition function, though,
       * since we disallow transitions back to NULL when there is one.
       */
      MemoryContextSwitchTo(oldContext);
      Assert(!OidIsValid(peraggstate->invtransfn_oid));
      return;
    }
  }

  /*
   * OK to call the transition function.  Set winstate->curaggcontext while
   * calling it, for possible use by AggCheckCallContext.
   */
  InitFunctionCallInfoData(*fcinfo, &(peraggstate->transfn),
               numArguments + 1,
               perfuncstate->winCollation,
               (Node *) winstate, NULL);
  fcinfo->args[0].value = peraggstate->transValue;
  fcinfo->args[0].isnull = peraggstate->transValueIsNull;
  winstate->curaggcontext = peraggstate->aggcontext;
  newVal = FunctionCallInvoke(fcinfo);
  winstate->curaggcontext = NULL;

  /*
   * Moving-aggregate transition functions must not return null, see
   * advance_windowaggregate_base().
   */
  if (fcinfo->isnull && OidIsValid(peraggstate->invtransfn_oid))
    ereport(ERROR,
        (errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
         errmsg("moving-aggregate transition function must not return null")));

  /*
   * We must track the number of rows included in transValue, since to
   * remove the last input, advance_windowaggregate_base() mustn't call the
   * inverse transition function, but simply reset transValue back to its
   * initial value.
   */
  peraggstate->transValueCount++;

  /*
   * If pass-by-ref datatype, must copy the new value into aggcontext and
   * free the prior transValue.  But if transfn returned a pointer to its
   * first input, we don't need to do anything.  Also, if transfn returned a
   * pointer to a R/W expanded object that is already a child of the
   * aggcontext, assume we can adopt that value without copying it.  (See
   * comments for ExecAggCopyTransValue, which this code duplicates.)
   */
  if (!peraggstate->transtypeByVal &&
    DatumGetPointer(newVal) != DatumGetPointer(peraggstate->transValue))
  {
    if (!fcinfo->isnull)
    {
      MemoryContextSwitchTo(peraggstate->aggcontext);
      if (DatumIsReadWriteExpandedObject(newVal,
                         false,
                         peraggstate->transtypeLen) &&
        MemoryContextGetParent(DatumGetEOHP(newVal)->eoh_context) == CurrentMemoryContext)
         /* do nothing */ ;
      else
        newVal = datumCopy(newVal,
                   peraggstate->transtypeByVal,
                   peraggstate->transtypeLen);
    }
    if (!peraggstate->transValueIsNull)
    {
      if (DatumIsReadWriteExpandedObject(peraggstate->transValue,
                         false,
                         peraggstate->transtypeLen))
        DeleteExpandedObject(peraggstate->transValue);
      else
        pfree(DatumGetPointer(peraggstate->transValue));
    }
  }

  MemoryContextSwitchTo(oldContext);
  peraggstate->transValue = newVal;
  peraggstate->transValueIsNull = fcinfo->isnull;
}

/*
 * advance_windowaggregate_base
 * Remove the oldest tuple from an aggregation.
 *
 * This is very much like advance_windowaggregate, except that we will call
 * the inverse transition function (which caller must have checked is
 * available).
 *
 * Returns true if we successfully removed the current row from this
 * aggregate, false if not (in the latter case, caller is responsible
 * for cleaning up by restarting the aggregation).
 */
static bool
advance_windowaggregate_base(WindowAggState *winstate,
               WindowStatePerFunc perfuncstate,
               WindowStatePerAgg peraggstate)
{
  LOCAL_FCINFO(fcinfo, FUNC_MAX_ARGS);
  WindowFuncExprState *wfuncstate = perfuncstate->wfuncstate;
  int     numArguments = perfuncstate->numArguments;
  Datum   newVal;
  ListCell   *arg;
  int     i;
  MemoryContext oldContext;
  ExprContext *econtext = winstate->tmpcontext;
  ExprState  *filter = wfuncstate->aggfilter;

  oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);

  /* Skip anything FILTERed out */
  if (filter)
  {
    bool    isnull;
    Datum   res = ExecEvalExpr(filter, econtext, &isnull);

    if (isnull || !DatumGetBool(res))
    {
      MemoryContextSwitchTo(oldContext);
      return true;
    }
  }

  /* We start from 1, since the 0th arg will be the transition value */
  i = 1;
  foreach(arg, wfuncstate->args)
  {
    ExprState  *argstate = (ExprState *) lfirst(arg);

    fcinfo->args[i].value = ExecEvalExpr(argstate, econtext,
                       &fcinfo->args[i].isnull);
    i++;
  }

  if (peraggstate->invtransfn.fn_strict)
  {
    /*
     * For a strict (inv)transfn, nothing happens when there's a NULL
     * input; we just keep the prior transValue.  Note transValueCount
     * doesn't change either.
     */
    for (i = 1; i <= numArguments; i++)
    {
      if (fcinfo->args[i].isnull)
      {
        MemoryContextSwitchTo(oldContext);
        return true;
      }
    }
  }

  /* There should still be an added but not yet removed value */
  Assert(peraggstate->transValueCount > 0);

  /*
   * In moving-aggregate mode, the state must never be NULL, except possibly
   * before any rows have been aggregated (which is surely not the case at
   * this point).  This restriction allows us to interpret a NULL result
   * from the inverse function as meaning "sorry, can't do an inverse
   * transition in this case".  We already checked this in
   * advance_windowaggregate, but just for safety, check again.
   */
  if (peraggstate->transValueIsNull)
    elog(ERROR, "aggregate transition value is NULL before inverse transition");

  /*
   * We mustn't use the inverse transition function to remove the last
   * input.  Doing so would yield a non-NULL state, whereas we should be in
   * the initial state afterwards which may very well be NULL.  So instead,
   * we simply re-initialize the aggregate in this case.
   */
  if (peraggstate->transValueCount == 1)
  {
    MemoryContextSwitchTo(oldContext);
    initialize_windowaggregate(winstate,
                   &winstate->perfunc[peraggstate->wfuncno],
                   peraggstate);
    return true;
  }

  /*
   * OK to call the inverse transition function.  Set
   * winstate->curaggcontext while calling it, for possible use by
   * AggCheckCallContext.
   */
  InitFunctionCallInfoData(*fcinfo, &(peraggstate->invtransfn),
               numArguments + 1,
               perfuncstate->winCollation,
               (Node *) winstate, NULL);
  fcinfo->args[0].value = peraggstate->transValue;
  fcinfo->args[0].isnull = peraggstate->transValueIsNull;
  winstate->curaggcontext = peraggstate->aggcontext;
  newVal = FunctionCallInvoke(fcinfo);
  winstate->curaggcontext = NULL;

  /*
   * If the function returns NULL, report failure, forcing a restart.
   */
  if (fcinfo->isnull)
  {
    MemoryContextSwitchTo(oldContext);
    return false;
  }

  /* Update number of rows included in transValue */
  peraggstate->transValueCount--;

  /*
   * If pass-by-ref datatype, must copy the new value into aggcontext and
   * free the prior transValue.  But if invtransfn returned a pointer to its
   * first input, we don't need to do anything.  Also, if invtransfn
   * returned a pointer to a R/W expanded object that is already a child of
   * the aggcontext, assume we can adopt that value without copying it. (See
   * comments for ExecAggCopyTransValue, which this code duplicates.)
   *
   * Note: the checks for null values here will never fire, but it seems
   * best to have this stanza look just like advance_windowaggregate.
   */
  if (!peraggstate->transtypeByVal &&
    DatumGetPointer(newVal) != DatumGetPointer(peraggstate->transValue))
  {
    if (!fcinfo->isnull)
    {
      MemoryContextSwitchTo(peraggstate->aggcontext);
      if (DatumIsReadWriteExpandedObject(newVal,
                         false,
                         peraggstate->transtypeLen) &&
        MemoryContextGetParent(DatumGetEOHP(newVal)->eoh_context) == CurrentMemoryContext)
         /* do nothing */ ;
      else
        newVal = datumCopy(newVal,
                   peraggstate->transtypeByVal,
                   peraggstate->transtypeLen);
    }
    if (!peraggstate->transValueIsNull)
    {
      if (DatumIsReadWriteExpandedObject(peraggstate->transValue,
                         false,
                         peraggstate->transtypeLen))
        DeleteExpandedObject(peraggstate->transValue);
      else
        pfree(DatumGetPointer(peraggstate->transValue));
    }
  }

  MemoryContextSwitchTo(oldContext);
  peraggstate->transValue = newVal;
  peraggstate->transValueIsNull = fcinfo->isnull;

  return true;
}

/*
 * finalize_windowaggregate
 * parallel to finalize_aggregate in nodeAgg.c
 */
static void
finalize_windowaggregate(WindowAggState *winstate,
             WindowStatePerFunc perfuncstate,
             WindowStatePerAgg peraggstate,
             Datum *result, bool *isnull)
{
  MemoryContext oldContext;

  oldContext = MemoryContextSwitchTo(winstate->ss.ps.ps_ExprContext->ecxt_per_tuple_memory);

  /*
   * Apply the agg's finalfn if one is provided, else return transValue.
   */
  if (OidIsValid(peraggstate->finalfn_oid))
  {
    LOCAL_FCINFO(fcinfo, FUNC_MAX_ARGS);
    int     numFinalArgs = peraggstate->numFinalArgs;
    bool    anynull;
    int     i;

    InitFunctionCallInfoData(fcinfodata.fcinfo, &(peraggstate->finalfn),
                 numFinalArgs,
                 perfuncstate->winCollation,
                 (Node *) winstate, NULL);
    fcinfo->args[0].value =
      MakeExpandedObjectReadOnly(peraggstate->transValue,
                     peraggstate->transValueIsNull,
                     peraggstate->transtypeLen);
    fcinfo->args[0].isnull = peraggstate->transValueIsNull;
    anynull = peraggstate->transValueIsNull;

    /* Fill any remaining argument positions with nulls */
    for (i = 1; i < numFinalArgs; i++)
    {
      fcinfo->args[i].value = (Datum) 0;
      fcinfo->args[i].isnull = true;
      anynull = true;
    }

    if (fcinfo->flinfo->fn_strict && anynull)
    {
      /* don't call a strict function with NULL inputs */
      *result = (Datum) 0;
      *isnull = true;
    }
    else
    {
      Datum   res;

      winstate->curaggcontext = peraggstate->aggcontext;
      res = FunctionCallInvoke(fcinfo);
      winstate->curaggcontext = NULL;
      *isnull = fcinfo->isnull;
      *result = MakeExpandedObjectReadOnly(res,
                         fcinfo->isnull,
                         peraggstate->resulttypeLen);
    }
  }
  else
  {
    *result =
      MakeExpandedObjectReadOnly(peraggstate->transValue,
                     peraggstate->transValueIsNull,
                     peraggstate->transtypeLen);
    *isnull = peraggstate->transValueIsNull;
  }

  MemoryContextSwitchTo(oldContext);
}

/*
 * eval_windowaggregates
 * evaluate plain aggregates being used as window functions
 *
 * This differs from nodeAgg.c in two ways.  First, if the window's frame
 * start position moves, we use the inverse transition function (if it exists)
 * to remove rows from the transition value.  And second, we expect to be
 * able to call aggregate final functions repeatedly after aggregating more
 * data onto the same transition value.  This is not a behavior required by
 * nodeAgg.c.
 */
static void
eval_windowaggregates(WindowAggState *winstate)
{
  WindowStatePerAgg peraggstate;
  int     wfuncno,
        numaggs,
        numaggs_restart,
        i;
  int64   aggregatedupto_nonrestarted;
  MemoryContext oldContext;
  ExprContext *econtext;
  WindowObject agg_winobj;
  TupleTableSlot *agg_row_slot;
  TupleTableSlot *temp_slot;

  numaggs = winstate->numaggs;
  if (numaggs == 0)
    return;         /* nothing to do */

  /* final output execution is in ps_ExprContext */
  econtext = winstate->ss.ps.ps_ExprContext;
  agg_winobj = winstate->agg_winobj;
  agg_row_slot = winstate->agg_row_slot;
  temp_slot = winstate->temp_slot_1;

  /*
   * If the window's frame start clause is UNBOUNDED_PRECEDING and no
   * exclusion clause is specified, then the window frame consists of a
   * contiguous group of rows extending forward from the start of the
   * partition, and rows only enter the frame, never exit it, as the current
   * row advances forward.  This makes it possible to use an incremental
   * strategy for evaluating aggregates: we run the transition function for
   * each row added to the frame, and run the final function whenever we
   * need the current aggregate value.  This is considerably more efficient
   * than the naive approach of re-running the entire aggregate calculation
   * for each current row.  It does assume that the final function doesn't
   * damage the running transition value, but we have the same assumption in
   * nodeAgg.c too (when it rescans an existing hash table).
   *
   * If the frame start does sometimes move, we can still optimize as above
   * whenever successive rows share the same frame head, but if the frame
   * head moves beyond the previous head we try to remove those rows using
   * the aggregate's inverse transition function.  This function restores
   * the aggregate's current state to what it would be if the removed row
   * had never been aggregated in the first place.  Inverse transition
   * functions may optionally return NULL, indicating that the function was
   * unable to remove the tuple from aggregation.  If this happens, or if
   * the aggregate doesn't have an inverse transition function at all, we
   * must perform the aggregation all over again for all tuples within the
   * new frame boundaries.
   *
   * If there's any exclusion clause, then we may have to aggregate over a
   * non-contiguous set of rows, so we punt and recalculate for every row.
   * (For some frame end choices, it might be that the frame is always
   * contiguous anyway, but that's an optimization to investigate later.)
   *
   * In many common cases, multiple rows share the same frame and hence the
   * same aggregate value. (In particular, if there's no ORDER BY in a RANGE
   * window, then all rows are peers and so they all have window frame equal
   * to the whole partition.)  We optimize such cases by calculating the
   * aggregate value once when we reach the first row of a peer group, and
   * then returning the saved value for all subsequent rows.
   *
   * 'aggregatedupto' keeps track of the first row that has not yet been
   * accumulated into the aggregate transition values.  Whenever we start a
   * new peer group, we accumulate forward to the end of the peer group.
   */

  /*
   * First, update the frame head position.
   *
   * The frame head should never move backwards, and the code below wouldn't
   * cope if it did, so for safety we complain if it does.
   */
  update_frameheadpos(winstate);
  if (winstate->frameheadpos < winstate->aggregatedbase)
    elog(ERROR, "window frame head moved backward");

  /*
   * If the frame didn't change compared to the previous row, we can re-use
   * the result values that were previously saved at the bottom of this
   * function.  Since we don't know the current frame's end yet, this is not
   * possible to check for fully.  But if the frame end mode is UNBOUNDED
   * FOLLOWING or CURRENT ROW, no exclusion clause is specified, and the
   * current row lies within the previous row's frame, then the two frames'
   * ends must coincide.  Note that on the first row aggregatedbase ==
   * aggregatedupto, meaning this test must fail, so we don't need to check
   * the "there was no previous row" case explicitly here.
   */
  if (winstate->aggregatedbase == winstate->frameheadpos &&
    (winstate->frameOptions & (FRAMEOPTION_END_UNBOUNDED_FOLLOWING |
                   FRAMEOPTION_END_CURRENT_ROW)) &&
    !(winstate->frameOptions & FRAMEOPTION_EXCLUSION) &&
    winstate->aggregatedbase <= winstate->currentpos &&
    winstate->aggregatedupto > winstate->currentpos)
  {
    for (i = 0; i < numaggs; i++)
    {
      peraggstate = &winstate->peragg[i];
      wfuncno = peraggstate->wfuncno;
      econtext->ecxt_aggvalues[wfuncno] = peraggstate->resultValue;
      econtext->ecxt_aggnulls[wfuncno] = peraggstate->resultValueIsNull;
    }
    return;
  }

  /*----------
   * Initialize restart flags.
   *
   * We restart the aggregation:
   *   - if we're processing the first row in the partition, or
   *   - if the frame's head moved and we cannot use an inverse
   *     transition function, or
   *   - we have an EXCLUSION clause, or
   *   - if the new frame doesn't overlap the old one
   *
   * Note that we don't strictly need to restart in the last case, but if
   * we're going to remove all rows from the aggregation anyway, a restart
   * surely is faster.
   *----------
   */
  numaggs_restart = 0;
  for (i = 0; i < numaggs; i++)
  {
    peraggstate = &winstate->peragg[i];
    if (winstate->currentpos == 0 ||
      (winstate->aggregatedbase != winstate->frameheadpos &&
       !OidIsValid(peraggstate->invtransfn_oid)) ||
      (winstate->frameOptions & FRAMEOPTION_EXCLUSION) ||
      winstate->aggregatedupto <= winstate->frameheadpos)
    {
      peraggstate->restart = true;
      numaggs_restart++;
    }
    else
      peraggstate->restart = false;
  }

  /*
   * If we have any possibly-moving aggregates, attempt to advance
   * aggregatedbase to match the frame's head by removing input rows that
   * fell off the top of the frame from the aggregations.  This can fail,
   * i.e. advance_windowaggregate_base() can return false, in which case
   * we'll restart that aggregate below.
   */
  while (numaggs_restart < numaggs &&
       winstate->aggregatedbase < winstate->frameheadpos)
  {
    /*
     * Fetch the next tuple of those being removed. This should never fail
     * as we should have been here before.
     */
    if (!window_gettupleslot(agg_winobj, winstate->aggregatedbase,
                 temp_slot))
      elog(ERROR, "could not re-fetch previously fetched frame row");

    /* Set tuple context for evaluation of aggregate arguments */
    winstate->tmpcontext->ecxt_outertuple = temp_slot;

    /*
     * Perform the inverse transition for each aggregate function in the
     * window, unless it has already been marked as needing a restart.
     */
    for (i = 0; i < numaggs; i++)
    {
      bool    ok;

      peraggstate = &winstate->peragg[i];
      if (peraggstate->restart)
        continue;

      wfuncno = peraggstate->wfuncno;
      ok = advance_windowaggregate_base(winstate,
                        &winstate->perfunc[wfuncno],
                        peraggstate);
      if (!ok)
      {
        /* Inverse transition function has failed, must restart */
        peraggstate->restart = true;
        numaggs_restart++;
      }
    }

    /* Reset per-input-tuple context after each tuple */
    ResetExprContext(winstate->tmpcontext);

    /* And advance the aggregated-row state */
    winstate->aggregatedbase++;
    ExecClearTuple(temp_slot);
  }

  /*
   * If we successfully advanced the base rows of all the aggregates,
   * aggregatedbase now equals frameheadpos; but if we failed for any, we
   * must forcibly update aggregatedbase.
   */
  winstate->aggregatedbase = winstate->frameheadpos;

  /*
   * If we created a mark pointer for aggregates, keep it pushed up to frame
   * head, so that tuplestore can discard unnecessary rows.
   */
  if (agg_winobj->markptr >= 0)
    WinSetMarkPosition(agg_winobj, winstate->frameheadpos);

  /*
   * Now restart the aggregates that require it.
   *
   * We assume that aggregates using the shared context always restart if
   * *any* aggregate restarts, and we may thus clean up the shared
   * aggcontext if that is the case.  Private aggcontexts are reset by
   * initialize_windowaggregate() if their owning aggregate restarts. If we
   * aren't restarting an aggregate, we need to free any previously saved
   * result for it, else we'll leak memory.
   */
  if (numaggs_restart > 0)
    MemoryContextReset(winstate->aggcontext);
  for (i = 0; i < numaggs; i++)
  {
    peraggstate = &winstate->peragg[i];

    /* Aggregates using the shared ctx must restart if *any* agg does */
    Assert(peraggstate->aggcontext != winstate->aggcontext ||
         numaggs_restart == 0 ||
         peraggstate->restart);

    if (peraggstate->restart)
    {
      wfuncno = peraggstate->wfuncno;
      initialize_windowaggregate(winstate,
                     &winstate->perfunc[wfuncno],
                     peraggstate);
    }
    else if (!peraggstate->resultValueIsNull)
    {
      if (!peraggstate->resulttypeByVal)
        pfree(DatumGetPointer(peraggstate->resultValue));
      peraggstate->resultValue = (Datum) 0;
      peraggstate->resultValueIsNull = true;
    }
  }

  /*
   * Non-restarted aggregates now contain the rows between aggregatedbase
   * (i.e., frameheadpos) and aggregatedupto, while restarted aggregates
   * contain no rows.  If there are any restarted aggregates, we must thus
   * begin aggregating anew at frameheadpos, otherwise we may simply
   * continue at aggregatedupto.  We must remember the old value of
   * aggregatedupto to know how long to skip advancing non-restarted
   * aggregates.  If we modify aggregatedupto, we must also clear
   * agg_row_slot, per the loop invariant below.
   */
  aggregatedupto_nonrestarted = winstate->aggregatedupto;
  if (numaggs_restart > 0 &&
    winstate->aggregatedupto != winstate->frameheadpos)
  {
    winstate->aggregatedupto = winstate->frameheadpos;
    ExecClearTuple(agg_row_slot);
  }

  /*
   * Advance until we reach a row not in frame (or end of partition).
   *
   * Note the loop invariant: agg_row_slot is either empty or holds the row
   * at position aggregatedupto.  We advance aggregatedupto after processing
   * a row.
   */
  for (;;)
  {
    int     ret;

    /* Fetch next row if we didn't already */
    if (TupIsNull(agg_row_slot))
    {
      if (!window_gettupleslot(agg_winobj, winstate->aggregatedupto,
                   agg_row_slot))
        break;     /* must be end of partition */
    }

    /*
     * Exit loop if no more rows can be in frame.  Skip aggregation if
     * current row is not in frame but there might be more in the frame.
     */
    ret = row_is_in_frame(winstate, winstate->aggregatedupto, agg_row_slot);
    if (ret < 0)
      break;
    if (ret == 0)
      goto next_tuple;

    /* Set tuple context for evaluation of aggregate arguments */
    winstate->tmpcontext->ecxt_outertuple = agg_row_slot;

    /* Accumulate row into the aggregates */
    for (i = 0; i < numaggs; i++)
    {
      peraggstate = &winstate->peragg[i];

      /* Non-restarted aggs skip until aggregatedupto_nonrestarted */
      if (!peraggstate->restart &&
        winstate->aggregatedupto < aggregatedupto_nonrestarted)
        continue;

      wfuncno = peraggstate->wfuncno;
      advance_windowaggregate(winstate,
                  &winstate->perfunc[wfuncno],
                  peraggstate);
    }

next_tuple:
    /* Reset per-input-tuple context after each tuple */
    ResetExprContext(winstate->tmpcontext);

    /* And advance the aggregated-row state */
    winstate->aggregatedupto++;
    ExecClearTuple(agg_row_slot);
  }

  /* The frame's end is not supposed to move backwards, ever */
  Assert(aggregatedupto_nonrestarted <= winstate->aggregatedupto);

  /*
   * finalize aggregates and fill result/isnull fields.
   */
  for (i = 0; i < numaggs; i++)
  {
    Datum    *result;
    bool     *isnull;

    peraggstate = &winstate->peragg[i];
    wfuncno = peraggstate->wfuncno;
    result = &econtext->ecxt_aggvalues[wfuncno];
    isnull = &econtext->ecxt_aggnulls[wfuncno];
    finalize_windowaggregate(winstate,
                 &winstate->perfunc[wfuncno],
                 peraggstate,
                 result, isnull);

    /*
     * save the result in case next row shares the same frame.
     *
     * XXX in some framing modes, eg ROWS/END_CURRENT_ROW, we can know in
     * advance that the next row can't possibly share the same frame. Is
     * it worth detecting that and skipping this code?
     */
    if (!peraggstate->resulttypeByVal && !*isnull)
    {
      oldContext = MemoryContextSwitchTo(peraggstate->aggcontext);
      peraggstate->resultValue =
        datumCopy(*result,
              peraggstate->resulttypeByVal,
              peraggstate->resulttypeLen);
      MemoryContextSwitchTo(oldContext);
    }
    else
    {
      peraggstate->resultValue = *result;
    }
    peraggstate->resultValueIsNull = *isnull;
  }
}

/*
 * eval_windowfunction
 *
 * Arguments of window functions are not evaluated here, because a window
 * function can need random access to arbitrary rows in the partition.
 * The window function uses the special WinGetFuncArgInPartition and
 * WinGetFuncArgInFrame functions to evaluate the arguments for the rows
 * it wants.
 */
static void
eval_windowfunction(WindowAggState *winstate, WindowStatePerFunc perfuncstate,
          Datum *result, bool *isnull)
{
  LOCAL_FCINFO(fcinfo, FUNC_MAX_ARGS);
  MemoryContext oldContext;

  oldContext = MemoryContextSwitchTo(winstate->ss.ps.ps_ExprContext->ecxt_per_tuple_memory);

  /*
   * We don't pass any normal arguments to a window function, but we do pass
   * it the number of arguments, in order to permit window function
   * implementations to support varying numbers of arguments.  The real info
   * goes through the WindowObject, which is passed via fcinfo->context.
   */
  InitFunctionCallInfoData(*fcinfo, &(perfuncstate->flinfo),
               perfuncstate->numArguments,
               perfuncstate->winCollation,
               (Node *) perfuncstate->winobj, NULL);
  /* Just in case, make all the regular argument slots be null */
  for (int argno = 0; argno < perfuncstate->numArguments; argno++)
    fcinfo->args[argno].isnull = true;
  /* Window functions don't have a current aggregate context, either */
  winstate->curaggcontext = NULL;

  *result = FunctionCallInvoke(fcinfo);
  *isnull = fcinfo->isnull;

  /*
   * The window function might have returned a pass-by-ref result that's
   * just a pointer into one of the WindowObject's temporary slots.  That's
   * not a problem if it's the only window function using the WindowObject;
   * but if there's more than one function, we'd better copy the result to
   * ensure it's not clobbered by later window functions.
   */
  if (!perfuncstate->resulttypeByVal && !fcinfo->isnull &&
    winstate->numfuncs > 1)
    *result = datumCopy(*result,
              perfuncstate->resulttypeByVal,
              perfuncstate->resulttypeLen);

  MemoryContextSwitchTo(oldContext);
}

/*
 * prepare_tuplestore
 *    Prepare the tuplestore and all of the required read pointers for the
 *    WindowAggState's frameOptions.
 *
 * Note: We use pg_noinline to avoid bloating the calling function with code
 * which is only called once.
 */
static pg_noinline void
prepare_tuplestore(WindowAggState *winstate)
{
  WindowAgg  *node = (WindowAgg *) winstate->ss.ps.plan;
  int     frameOptions = winstate->frameOptions;
  int     numfuncs = winstate->numfuncs;

  /* we shouldn't be called if this was done already */
  Assert(winstate->buffer == NULL);

  /* Create new tuplestore */
  winstate->buffer = tuplestore_begin_heap(false, false, work_mem);

  /*
   * Set up read pointers for the tuplestore.  The current pointer doesn't
   * need BACKWARD capability, but the per-window-function read pointers do,
   * and the aggregate pointer does if we might need to restart aggregation.
   */
  winstate->current_ptr = 0;  /* read pointer 0 is pre-allocated */

  /* reset default REWIND capability bit for current ptr */
  tuplestore_set_eflags(winstate->buffer, 0);

  /* create read pointers for aggregates, if needed */
  if (winstate->numaggs > 0)
  {
    WindowObject agg_winobj = winstate->agg_winobj;
    int     readptr_flags = 0;

    /*
     * If the frame head is potentially movable, or we have an EXCLUSION
     * clause, we might need to restart aggregation ...
     */
    if (!(frameOptions & FRAMEOPTION_START_UNBOUNDED_PRECEDING) ||
      (frameOptions & FRAMEOPTION_EXCLUSION))
    {
      /* ... so create a mark pointer to track the frame head */
      agg_winobj->markptr = tuplestore_alloc_read_pointer(winstate->buffer, 0);
      /* and the read pointer will need BACKWARD capability */
      readptr_flags |= EXEC_FLAG_BACKWARD;
    }

    agg_winobj->readptr = tuplestore_alloc_read_pointer(winstate->buffer,
                              readptr_flags);
  }

  /* create mark and read pointers for each real window function */
  for (int i = 0; i < numfuncs; i++)
  {
    WindowStatePerFunc perfuncstate = &(winstate->perfunc[i]);

    if (!perfuncstate->plain_agg)
    {
      WindowObject winobj = perfuncstate->winobj;

      winobj->markptr = tuplestore_alloc_read_pointer(winstate->buffer,
                              0);
      winobj->readptr = tuplestore_alloc_read_pointer(winstate->buffer,
                              EXEC_FLAG_BACKWARD);
    }
  }

  /*
   * If we are in RANGE or GROUPS mode, then determining frame boundaries
   * requires physical access to the frame endpoint rows, except in certain
   * degenerate cases.  We create read pointers to point to those rows, to
   * simplify access and ensure that the tuplestore doesn't discard the
   * endpoint rows prematurely.  (Must create pointers in exactly the same
   * cases that update_frameheadpos and update_frametailpos need them.)
   */
  winstate->framehead_ptr = winstate->frametail_ptr = -1; /* if not used */

  if (frameOptions & (FRAMEOPTION_RANGE | FRAMEOPTION_GROUPS))
  {
    if (((frameOptions & FRAMEOPTION_START_CURRENT_ROW) &&
       node->ordNumCols != 0) ||
      (frameOptions & FRAMEOPTION_START_OFFSET))
      winstate->framehead_ptr =
        tuplestore_alloc_read_pointer(winstate->buffer, 0);
    if (((frameOptions & FRAMEOPTION_END_CURRENT_ROW) &&
       node->ordNumCols != 0) ||
      (frameOptions & FRAMEOPTION_END_OFFSET))
      winstate->frametail_ptr =
        tuplestore_alloc_read_pointer(winstate->buffer, 0);
  }

  /*
   * If we have an exclusion clause that requires knowing the boundaries of
   * the current row's peer group, we create a read pointer to track the
   * tail position of the peer group (i.e., first row of the next peer
   * group).  The head position does not require its own pointer because we
   * maintain that as a side effect of advancing the current row.
   */
  winstate->grouptail_ptr = -1;

  if ((frameOptions & (FRAMEOPTION_EXCLUDE_GROUP |
             FRAMEOPTION_EXCLUDE_TIES)) &&
    node->ordNumCols != 0)
  {
    winstate->grouptail_ptr =
      tuplestore_alloc_read_pointer(winstate->buffer, 0);
  }
}

/*
 * begin_partition
 * Start buffering rows of the next partition.
 */
static void
begin_partition(WindowAggState *winstate)
{
  PlanState  *outerPlan = outerPlanState(winstate);
  int     numfuncs = winstate->numfuncs;

  winstate->partition_spooled = false;
  winstate->framehead_valid = false;
  winstate->frametail_valid = false;
  winstate->grouptail_valid = false;
  winstate->spooled_rows = 0;
  winstate->currentpos = 0;
  winstate->frameheadpos = 0;
  winstate->frametailpos = 0;
  winstate->currentgroup = 0;
  winstate->frameheadgroup = 0;
  winstate->frametailgroup = 0;
  winstate->groupheadpos = 0;
  winstate->grouptailpos = -1;  /* see update_grouptailpos */
  ExecClearTuple(winstate->agg_row_slot);
  if (winstate->framehead_slot)
    ExecClearTuple(winstate->framehead_slot);
  if (winstate->frametail_slot)
    ExecClearTuple(winstate->frametail_slot);

  /*
   * If this is the very first partition, we need to fetch the first input
   * row to store in first_part_slot.
   */
  if (TupIsNull(winstate->first_part_slot))
  {
    TupleTableSlot *outerslot = ExecProcNode(outerPlan);

    if (!TupIsNull(outerslot))
      ExecCopySlot(winstate->first_part_slot, outerslot);
    else
    {
      /* outer plan is empty, so we have nothing to do */
      winstate->partition_spooled = true;
      winstate->more_partitions = false;
      return;
    }
  }

  /* Create new tuplestore if not done already. */
  if (unlikely(winstate->buffer == NULL))
    prepare_tuplestore(winstate);

  winstate->next_partition = false;

  if (winstate->numaggs > 0)
  {
    WindowObject agg_winobj = winstate->agg_winobj;

    /* reset mark and see positions for aggregate functions */
    agg_winobj->markpos = -1;
    agg_winobj->seekpos = -1;

    /* Also reset the row counters for aggregates */
    winstate->aggregatedbase = 0;
    winstate->aggregatedupto = 0;
  }

  /* reset mark and seek positions for each real window function */
  for (int i = 0; i < numfuncs; i++)
  {
    WindowStatePerFunc perfuncstate = &(winstate->perfunc[i]);

    if (!perfuncstate->plain_agg)
    {
      WindowObject winobj = perfuncstate->winobj;

      winobj->markpos = -1;
      winobj->seekpos = -1;
    }
  }

  /*
   * Store the first tuple into the tuplestore (it's always available now;
   * we either read it above, or saved it at the end of previous partition)
   */
  tuplestore_puttupleslot(winstate->buffer, winstate->first_part_slot);
  winstate->spooled_rows++;
}

/*
 * Read tuples from the outer node, up to and including position 'pos', and
 * store them into the tuplestore. If pos is -1, reads the whole partition.
 */
static void
spool_tuples(WindowAggState *winstate, int64 pos)
{
  WindowAgg  *node = (WindowAgg *) winstate->ss.ps.plan;
  PlanState  *outerPlan;
  TupleTableSlot *outerslot;
  MemoryContext oldcontext;

  if (!winstate->buffer)
    return;         /* just a safety check */
  if (winstate->partition_spooled)
    return;         /* whole partition done already */

  /*
   * When in pass-through mode we can just exhaust all tuples in the current
   * partition.  We don't need these tuples for any further window function
   * evaluation, however, we do need to keep them around if we're not the
   * top-level window as another WindowAgg node above must see these.
   */
  if (winstate->status != WINDOWAGG_RUN)
  {
    Assert(winstate->status == WINDOWAGG_PASSTHROUGH ||
         winstate->status == WINDOWAGG_PASSTHROUGH_STRICT);

    pos = -1;
  }

  /*
   * If the tuplestore has spilled to disk, alternate reading and writing
   * becomes quite expensive due to frequent buffer flushes.  It's cheaper
   * to force the entire partition to get spooled in one go.
   *
   * XXX this is a horrid kluge --- it'd be better to fix the performance
   * problem inside tuplestore.  FIXME
   */
  else if (!tuplestore_in_memory(winstate->buffer))
    pos = -1;

  outerPlan = outerPlanState(winstate);

  /* Must be in query context to call outerplan */
  oldcontext = MemoryContextSwitchTo(winstate->ss.ps.ps_ExprContext->ecxt_per_query_memory);

  while (winstate->spooled_rows <= pos || pos == -1)
  {
    outerslot = ExecProcNode(outerPlan);
    if (TupIsNull(outerslot))
    {
      /* reached the end of the last partition */
      winstate->partition_spooled = true;
      winstate->more_partitions = false;
      break;
    }

    if (node->partNumCols > 0)
    {
      ExprContext *econtext = winstate->tmpcontext;

      econtext->ecxt_innertuple = winstate->first_part_slot;
      econtext->ecxt_outertuple = outerslot;

      /* Check if this tuple still belongs to the current partition */
      if (!ExecQualAndReset(winstate->partEqfunction, econtext))
      {
        /*
         * end of partition; copy the tuple for the next cycle.
         */
        ExecCopySlot(winstate->first_part_slot, outerslot);
        winstate->partition_spooled = true;
        winstate->more_partitions = true;
        break;
      }
    }

    /*
     * Remember the tuple unless we're the top-level window and we're in
     * pass-through mode.
     */
    if (winstate->status != WINDOWAGG_PASSTHROUGH_STRICT)
    {
      /* Still in partition, so save it into the tuplestore */
      tuplestore_puttupleslot(winstate->buffer, outerslot);
      winstate->spooled_rows++;
    }
  }

  MemoryContextSwitchTo(oldcontext);
}

/*
 * release_partition
 * clear information kept within a partition, including
 * tuplestore and aggregate results.
 */
static void
release_partition(WindowAggState *winstate)
{
  int     i;

  for (i = 0; i < winstate->numfuncs; i++)
  {
    WindowStatePerFunc perfuncstate = &(winstate->perfunc[i]);

    /* Release any partition-local state of this window function */
    if (perfuncstate->winobj)
      perfuncstate->winobj->localmem = NULL;
  }

  /*
   * Release all partition-local memory (in particular, any partition-local
   * state that we might have trashed our pointers to in the above loop, and
   * any aggregate temp data).  We don't rely on retail pfree because some
   * aggregates might have allocated data we don't have direct pointers to.
   */
  MemoryContextReset(winstate->partcontext);
  MemoryContextReset(winstate->aggcontext);
  for (i = 0; i < winstate->numaggs; i++)
  {
    if (winstate->peragg[i].aggcontext != winstate->aggcontext)
      MemoryContextReset(winstate->peragg[i].aggcontext);
  }

  if (winstate->buffer)
    tuplestore_clear(winstate->buffer);
  winstate->partition_spooled = false;
  winstate->next_partition = true;
}

/*
 * row_is_in_frame
 * Determine whether a row is in the current row's window frame according
 * to our window framing rule
 *
 * The caller must have already determined that the row is in the partition
 * and fetched it into a slot.  This function just encapsulates the framing
 * rules.
 *
 * Returns:
 * -1, if the row is out of frame and no succeeding rows can be in frame
 * 0, if the row is out of frame but succeeding rows might be in frame
 * 1, if the row is in frame
 *
 * May clobber winstate->temp_slot_2.
 */
static int
row_is_in_frame(WindowAggState *winstate, int64 pos, TupleTableSlot *slot)
{
  int     frameOptions = winstate->frameOptions;

  Assert(pos >= 0);     /* else caller error */

  /*
   * First, check frame starting conditions.  We might as well delegate this
   * to update_frameheadpos always; it doesn't add any notable cost.
   */
  update_frameheadpos(winstate);
  if (pos < winstate->frameheadpos)
    return 0;

  /*
   * Okay so far, now check frame ending conditions.  Here, we avoid calling
   * update_frametailpos in simple cases, so as not to spool tuples further
   * ahead than necessary.
   */
  if (frameOptions & FRAMEOPTION_END_CURRENT_ROW)
  {
    if (frameOptions & FRAMEOPTION_ROWS)
    {
      /* rows after current row are out of frame */
      if (pos > winstate->currentpos)
        return -1;
    }
    else if (frameOptions & (FRAMEOPTION_RANGE | FRAMEOPTION_GROUPS))
    {
      /* following row that is not peer is out of frame */
      if (pos > winstate->currentpos &&
        !are_peers(winstate, slot, winstate->ss.ss_ScanTupleSlot))
        return -1;
    }
    else
      Assert(false);
  }
  else if (frameOptions & FRAMEOPTION_END_OFFSET)
  {
    if (frameOptions & FRAMEOPTION_ROWS)
    {
      int64   offset = DatumGetInt64(winstate->endOffsetValue);

      /* rows after current row + offset are out of frame */
      if (frameOptions & FRAMEOPTION_END_OFFSET_PRECEDING)
        offset = -offset;

      if (pos > winstate->currentpos + offset)
        return -1;
    }
    else if (frameOptions & (FRAMEOPTION_RANGE | FRAMEOPTION_GROUPS))
    {
      /* hard cases, so delegate to update_frametailpos */
      update_frametailpos(winstate);
      if (pos >= winstate->frametailpos)
        return -1;
    }
    else
      Assert(false);
  }

  /* Check exclusion clause */
  if (frameOptions & FRAMEOPTION_EXCLUDE_CURRENT_ROW)
  {
    if (pos == winstate->currentpos)
      return 0;
  }
  else if ((frameOptions & FRAMEOPTION_EXCLUDE_GROUP) ||
       ((frameOptions & FRAMEOPTION_EXCLUDE_TIES) &&
        pos != winstate->currentpos))
  {
    WindowAgg  *node = (WindowAgg *) winstate->ss.ps.plan;

    /* If no ORDER BY, all rows are peers with each other */
    if (node->ordNumCols == 0)
      return 0;
    /* Otherwise, check the group boundaries */
    if (pos >= winstate->groupheadpos)
    {
      update_grouptailpos(winstate);
      if (pos < winstate->grouptailpos)
        return 0;
    }
  }

  /* If we get here, it's in frame */
  return 1;
}

/*
 * update_frameheadpos
 * make frameheadpos valid for the current row
 *
 * Note that frameheadpos is computed without regard for any window exclusion
 * clause; the current row and/or its peers are considered part of the frame
 * for this purpose even if they must be excluded later.
 *
 * May clobber winstate->temp_slot_2.
 */
static void
update_frameheadpos(WindowAggState *winstate)
{
  WindowAgg  *node = (WindowAgg *) winstate->ss.ps.plan;
  int     frameOptions = winstate->frameOptions;
  MemoryContext oldcontext;

  if (winstate->framehead_valid)
    return;         /* already known for current row */

  /* We may be called in a short-lived context */
  oldcontext = MemoryContextSwitchTo(winstate->ss.ps.ps_ExprContext->ecxt_per_query_memory);

  if (frameOptions & FRAMEOPTION_START_UNBOUNDED_PRECEDING)
  {
    /* In UNBOUNDED PRECEDING mode, frame head is always row 0 */
    winstate->frameheadpos = 0;
    winstate->framehead_valid = true;
  }
  else if (frameOptions & FRAMEOPTION_START_CURRENT_ROW)
  {
    if (frameOptions & FRAMEOPTION_ROWS)
    {
      /* In ROWS mode, frame head is the same as current */
      winstate->frameheadpos = winstate->currentpos;
      winstate->framehead_valid = true;
    }
    else if (frameOptions & (FRAMEOPTION_RANGE | FRAMEOPTION_GROUPS))
    {
      /* If no ORDER BY, all rows are peers with each other */
      if (node->ordNumCols == 0)
      {
        winstate->frameheadpos = 0;
        winstate->framehead_valid = true;
        MemoryContextSwitchTo(oldcontext);
        return;
      }

      /*
       * In RANGE or GROUPS START_CURRENT_ROW mode, frame head is the
       * first row that is a peer of current row.  We keep a copy of the
       * last-known frame head row in framehead_slot, and advance as
       * necessary.  Note that if we reach end of partition, we will
       * leave frameheadpos = end+1 and framehead_slot empty.
       */
      tuplestore_select_read_pointer(winstate->buffer,
                       winstate->framehead_ptr);
      if (winstate->frameheadpos == 0 &&
        TupIsNull(winstate->framehead_slot))
      {
        /* fetch first row into framehead_slot, if we didn't already */
        if (!tuplestore_gettupleslot(winstate->buffer, true, true,
                       winstate->framehead_slot))
          elog(ERROR, "unexpected end of tuplestore");
      }

      while (!TupIsNull(winstate->framehead_slot))
      {
        if (are_peers(winstate, winstate->framehead_slot,
                winstate->ss.ss_ScanTupleSlot))
          break;   /* this row is the correct frame head */
        /* Note we advance frameheadpos even if the fetch fails */
        winstate->frameheadpos++;
        spool_tuples(winstate, winstate->frameheadpos);
        if (!tuplestore_gettupleslot(winstate->buffer, true, true,
                       winstate->framehead_slot))
          break;   /* end of partition */
      }
      winstate->framehead_valid = true;
    }
    else
      Assert(false);
  }
  else if (frameOptions & FRAMEOPTION_START_OFFSET)
  {
    if (frameOptions & FRAMEOPTION_ROWS)
    {
      /* In ROWS mode, bound is physically n before/after current */
      int64   offset = DatumGetInt64(winstate->startOffsetValue);

      if (frameOptions & FRAMEOPTION_START_OFFSET_PRECEDING)
        offset = -offset;

      winstate->frameheadpos = winstate->currentpos + offset;
      /* frame head can't go before first row */
      if (winstate->frameheadpos < 0)
        winstate->frameheadpos = 0;
      else if (winstate->frameheadpos > winstate->currentpos + 1)
      {
        /* make sure frameheadpos is not past end of partition */
        spool_tuples(winstate, winstate->frameheadpos - 1);
        if (winstate->frameheadpos > winstate->spooled_rows)
          winstate->frameheadpos = winstate->spooled_rows;
      }
      winstate->framehead_valid = true;
    }
    else if (frameOptions & FRAMEOPTION_RANGE)
    {
      /*
       * In RANGE START_OFFSET mode, frame head is the first row that
       * satisfies the in_range constraint relative to the current row.
       * We keep a copy of the last-known frame head row in
       * framehead_slot, and advance as necessary.  Note that if we
       * reach end of partition, we will leave frameheadpos = end+1 and
       * framehead_slot empty.
       */
      int     sortCol = node->ordColIdx[0];
      bool    sub,
            less;

      /* We must have an ordering column */
      Assert(node->ordNumCols == 1);

      /* Precompute flags for in_range checks */
      if (frameOptions & FRAMEOPTION_START_OFFSET_PRECEDING)
        sub = true;   /* subtract startOffset from current row */
      else
        sub = false; /* add it */
      less = false;   /* normally, we want frame head >= sum */
      /* If sort order is descending, flip both flags */
      if (!winstate->inRangeAsc)
      {
        sub = !sub;
        less = true;
      }

      tuplestore_select_read_pointer(winstate->buffer,
                       winstate->framehead_ptr);
      if (winstate->frameheadpos == 0 &&
        TupIsNull(winstate->framehead_slot))
      {
        /* fetch first row into framehead_slot, if we didn't already */
        if (!tuplestore_gettupleslot(winstate->buffer, true, true,
                       winstate->framehead_slot))
          elog(ERROR, "unexpected end of tuplestore");
      }

      while (!TupIsNull(winstate->framehead_slot))
      {
        Datum   headval,
              currval;
        bool    headisnull,
              currisnull;

        headval = slot_getattr(winstate->framehead_slot, sortCol,
                     &headisnull);
        currval = slot_getattr(winstate->ss.ss_ScanTupleSlot, sortCol,
                     &currisnull);
        if (headisnull || currisnull)
        {
          /* order of the rows depends only on nulls_first */
          if (winstate->inRangeNullsFirst)
          {
            /* advance head if head is null and curr is not */
            if (!headisnull || currisnull)
              break;
          }
          else
          {
            /* advance head if head is not null and curr is null */
            if (headisnull || !currisnull)
              break;
          }
        }
        else
        {
          if (DatumGetBool(FunctionCall5Coll(&winstate->startInRangeFunc,
                             winstate->inRangeColl,
                             headval,
                             currval,
                             winstate->startOffsetValue,
                             BoolGetDatum(sub),
                             BoolGetDatum(less))))
            break; /* this row is the correct frame head */
        }
        /* Note we advance frameheadpos even if the fetch fails */
        winstate->frameheadpos++;
        spool_tuples(winstate, winstate->frameheadpos);
        if (!tuplestore_gettupleslot(winstate->buffer, true, true,
                       winstate->framehead_slot))
          break;   /* end of partition */
      }
      winstate->framehead_valid = true;
    }
    else if (frameOptions & FRAMEOPTION_GROUPS)
    {
      /*
       * In GROUPS START_OFFSET mode, frame head is the first row of the
       * first peer group whose number satisfies the offset constraint.
       * We keep a copy of the last-known frame head row in
       * framehead_slot, and advance as necessary.  Note that if we
       * reach end of partition, we will leave frameheadpos = end+1 and
       * framehead_slot empty.
       */
      int64   offset = DatumGetInt64(winstate->startOffsetValue);
      int64   minheadgroup;

      if (frameOptions & FRAMEOPTION_START_OFFSET_PRECEDING)
        minheadgroup = winstate->currentgroup - offset;
      else
        minheadgroup = winstate->currentgroup + offset;

      tuplestore_select_read_pointer(winstate->buffer,
                       winstate->framehead_ptr);
      if (winstate->frameheadpos == 0 &&
        TupIsNull(winstate->framehead_slot))
      {
        /* fetch first row into framehead_slot, if we didn't already */
        if (!tuplestore_gettupleslot(winstate->buffer, true, true,
                       winstate->framehead_slot))
          elog(ERROR, "unexpected end of tuplestore");
      }

      while (!TupIsNull(winstate->framehead_slot))
      {
        if (winstate->frameheadgroup >= minheadgroup)
          break;   /* this row is the correct frame head */
        ExecCopySlot(winstate->temp_slot_2, winstate->framehead_slot);
        /* Note we advance frameheadpos even if the fetch fails */
        winstate->frameheadpos++;
        spool_tuples(winstate, winstate->frameheadpos);
        if (!tuplestore_gettupleslot(winstate->buffer, true, true,
                       winstate->framehead_slot))
          break;   /* end of partition */
        if (!are_peers(winstate, winstate->temp_slot_2,
                 winstate->framehead_slot))
          winstate->frameheadgroup++;
      }
      ExecClearTuple(winstate->temp_slot_2);
      winstate->framehead_valid = true;
    }
    else
      Assert(false);
  }
  else
    Assert(false);

  MemoryContextSwitchTo(oldcontext);
}

/*
 * update_frametailpos
 * make frametailpos valid for the current row
 *
 * Note that frametailpos is computed without regard for any window exclusion
 * clause; the current row and/or its peers are considered part of the frame
 * for this purpose even if they must be excluded later.
 *
 * May clobber winstate->temp_slot_2.
 */
static void
update_frametailpos(WindowAggState *winstate)
{
  WindowAgg  *node = (WindowAgg *) winstate->ss.ps.plan;
  int     frameOptions = winstate->frameOptions;
  MemoryContext oldcontext;

  if (winstate->frametail_valid)
    return;         /* already known for current row */

  /* We may be called in a short-lived context */
  oldcontext = MemoryContextSwitchTo(winstate->ss.ps.ps_ExprContext->ecxt_per_query_memory);

  if (frameOptions & FRAMEOPTION_END_UNBOUNDED_FOLLOWING)
  {
    /* In UNBOUNDED FOLLOWING mode, all partition rows are in frame */
    spool_tuples(winstate, -1);
    winstate->frametailpos = winstate->spooled_rows;
    winstate->frametail_valid = true;
  }
  else if (frameOptions & FRAMEOPTION_END_CURRENT_ROW)
  {
    if (frameOptions & FRAMEOPTION_ROWS)
    {
      /* In ROWS mode, exactly the rows up to current are in frame */
      winstate->frametailpos = winstate->currentpos + 1;
      winstate->frametail_valid = true;
    }
    else if (frameOptions & (FRAMEOPTION_RANGE | FRAMEOPTION_GROUPS))
    {
      /* If no ORDER BY, all rows are peers with each other */
      if (node->ordNumCols == 0)
      {
        spool_tuples(winstate, -1);
        winstate->frametailpos = winstate->spooled_rows;
        winstate->frametail_valid = true;
        MemoryContextSwitchTo(oldcontext);
        return;
      }

      /*
       * In RANGE or GROUPS END_CURRENT_ROW mode, frame end is the last
       * row that is a peer of current row, frame tail is the row after
       * that (if any).  We keep a copy of the last-known frame tail row
       * in frametail_slot, and advance as necessary.  Note that if we
       * reach end of partition, we will leave frametailpos = end+1 and
       * frametail_slot empty.
       */
      tuplestore_select_read_pointer(winstate->buffer,
                       winstate->frametail_ptr);
      if (winstate->frametailpos == 0 &&
        TupIsNull(winstate->frametail_slot))
      {
        /* fetch first row into frametail_slot, if we didn't already */
        if (!tuplestore_gettupleslot(winstate->buffer, true, true,
                       winstate->frametail_slot))
          elog(ERROR, "unexpected end of tuplestore");
      }

      while (!TupIsNull(winstate->frametail_slot))
      {
        if (winstate->frametailpos > winstate->currentpos &&
          !are_peers(winstate, winstate->frametail_slot,
                 winstate->ss.ss_ScanTupleSlot))
          break;   /* this row is the frame tail */
        /* Note we advance frametailpos even if the fetch fails */
        winstate->frametailpos++;
        spool_tuples(winstate, winstate->frametailpos);
        if (!tuplestore_gettupleslot(winstate->buffer, true, true,
                       winstate->frametail_slot))
          break;   /* end of partition */
      }
      winstate->frametail_valid = true;
    }
    else
      Assert(false);
  }
  else if (frameOptions & FRAMEOPTION_END_OFFSET)
  {
    if (frameOptions & FRAMEOPTION_ROWS)
    {
      /* In ROWS mode, bound is physically n before/after current */
      int64   offset = DatumGetInt64(winstate->endOffsetValue);

      if (frameOptions & FRAMEOPTION_END_OFFSET_PRECEDING)
        offset = -offset;

      winstate->frametailpos = winstate->currentpos + offset + 1;
      /* smallest allowable value of frametailpos is 0 */
      if (winstate->frametailpos < 0)
        winstate->frametailpos = 0;
      else if (winstate->frametailpos > winstate->currentpos + 1)
      {
        /* make sure frametailpos is not past end of partition */
        spool_tuples(winstate, winstate->frametailpos - 1);
        if (winstate->frametailpos > winstate->spooled_rows)
          winstate->frametailpos = winstate->spooled_rows;
      }
      winstate->frametail_valid = true;
    }
    else if (frameOptions & FRAMEOPTION_RANGE)
    {
      /*
       * In RANGE END_OFFSET mode, frame end is the last row that
       * satisfies the in_range constraint relative to the current row,
       * frame tail is the row after that (if any).  We keep a copy of
       * the last-known frame tail row in frametail_slot, and advance as
       * necessary.  Note that if we reach end of partition, we will
       * leave frametailpos = end+1 and frametail_slot empty.
       */
      int     sortCol = node->ordColIdx[0];
      bool    sub,
            less;

      /* We must have an ordering column */
      Assert(node->ordNumCols == 1);

      /* Precompute flags for in_range checks */
      if (frameOptions & FRAMEOPTION_END_OFFSET_PRECEDING)
        sub = true;   /* subtract endOffset from current row */
      else
        sub = false; /* add it */
      less = true;    /* normally, we want frame tail <= sum */
      /* If sort order is descending, flip both flags */
      if (!winstate->inRangeAsc)
      {
        sub = !sub;
        less = false;
      }

      tuplestore_select_read_pointer(winstate->buffer,
                       winstate->frametail_ptr);
      if (winstate->frametailpos == 0 &&
        TupIsNull(winstate->frametail_slot))
      {
        /* fetch first row into frametail_slot, if we didn't already */
        if (!tuplestore_gettupleslot(winstate->buffer, true, true,
                       winstate->frametail_slot))
          elog(ERROR, "unexpected end of tuplestore");
      }

      while (!TupIsNull(winstate->frametail_slot))
      {
        Datum   tailval,
              currval;
        bool    tailisnull,
              currisnull;

        tailval = slot_getattr(winstate->frametail_slot, sortCol,
                     &tailisnull);
        currval = slot_getattr(winstate->ss.ss_ScanTupleSlot, sortCol,
                     &currisnull);
        if (tailisnull || currisnull)
        {
          /* order of the rows depends only on nulls_first */
          if (winstate->inRangeNullsFirst)
          {
            /* advance tail if tail is null or curr is not */
            if (!tailisnull)
              break;
          }
          else
          {
            /* advance tail if tail is not null or curr is null */
            if (!currisnull)
              break;
          }
        }
        else
        {
          if (!DatumGetBool(FunctionCall5Coll(&winstate->endInRangeFunc,
                            winstate->inRangeColl,
                            tailval,
                            currval,
                            winstate->endOffsetValue,
                            BoolGetDatum(sub),
                            BoolGetDatum(less))))
            break; /* this row is the correct frame tail */
        }
        /* Note we advance frametailpos even if the fetch fails */
        winstate->frametailpos++;
        spool_tuples(winstate, winstate->frametailpos);
        if (!tuplestore_gettupleslot(winstate->buffer, true, true,
                       winstate->frametail_slot))
          break;   /* end of partition */
      }
      winstate->frametail_valid = true;
    }
    else if (frameOptions & FRAMEOPTION_GROUPS)
    {
      /*
       * In GROUPS END_OFFSET mode, frame end is the last row of the
       * last peer group whose number satisfies the offset constraint,
       * and frame tail is the row after that (if any).  We keep a copy
       * of the last-known frame tail row in frametail_slot, and advance
       * as necessary.  Note that if we reach end of partition, we will
       * leave frametailpos = end+1 and frametail_slot empty.
       */
      int64   offset = DatumGetInt64(winstate->endOffsetValue);
      int64   maxtailgroup;

      if (frameOptions & FRAMEOPTION_END_OFFSET_PRECEDING)
        maxtailgroup = winstate->currentgroup - offset;
      else
        maxtailgroup = winstate->currentgroup + offset;

      tuplestore_select_read_pointer(winstate->buffer,
                       winstate->frametail_ptr);
      if (winstate->frametailpos == 0 &&
        TupIsNull(winstate->frametail_slot))
      {
        /* fetch first row into frametail_slot, if we didn't already */
        if (!tuplestore_gettupleslot(winstate->buffer, true, true,
                       winstate->frametail_slot))
          elog(ERROR, "unexpected end of tuplestore");
      }

      while (!TupIsNull(winstate->frametail_slot))
      {
        if (winstate->frametailgroup > maxtailgroup)
          break;   /* this row is the correct frame tail */
        ExecCopySlot(winstate->temp_slot_2, winstate->frametail_slot);
        /* Note we advance frametailpos even if the fetch fails */
        winstate->frametailpos++;
        spool_tuples(winstate, winstate->frametailpos);
        if (!tuplestore_gettupleslot(winstate->buffer, true, true,
                       winstate->frametail_slot))
          break;   /* end of partition */
        if (!are_peers(winstate, winstate->temp_slot_2,
                 winstate->frametail_slot))
          winstate->frametailgroup++;
      }
      ExecClearTuple(winstate->temp_slot_2);
      winstate->frametail_valid = true;
    }
    else
      Assert(false);
  }
  else
    Assert(false);

  MemoryContextSwitchTo(oldcontext);
}

/*
 * update_grouptailpos
 * make grouptailpos valid for the current row
 *
 * May clobber winstate->temp_slot_2.
 */
static void
update_grouptailpos(WindowAggState *winstate)
{
  WindowAgg  *node = (WindowAgg *) winstate->ss.ps.plan;
  MemoryContext oldcontext;

  if (winstate->grouptail_valid)
    return;         /* already known for current row */

  /* We may be called in a short-lived context */
  oldcontext = MemoryContextSwitchTo(winstate->ss.ps.ps_ExprContext->ecxt_per_query_memory);

  /* If no ORDER BY, all rows are peers with each other */
  if (node->ordNumCols == 0)
  {
    spool_tuples(winstate, -1);
    winstate->grouptailpos = winstate->spooled_rows;
    winstate->grouptail_valid = true;
    MemoryContextSwitchTo(oldcontext);
    return;
  }

  /*
   * Because grouptail_valid is reset only when current row advances into a
   * new peer group, we always reach here knowing that grouptailpos needs to
   * be advanced by at least one row.  Hence, unlike the otherwise similar
   * case for frame tail tracking, we do not need persistent storage of the
   * group tail row.
   */
  Assert(winstate->grouptailpos <= winstate->currentpos);
  tuplestore_select_read_pointer(winstate->buffer,
                   winstate->grouptail_ptr);
  for (;;)
  {
    /* Note we advance grouptailpos even if the fetch fails */
    winstate->grouptailpos++;
    spool_tuples(winstate, winstate->grouptailpos);
    if (!tuplestore_gettupleslot(winstate->buffer, true, true,
                   winstate->temp_slot_2))
      break;       /* end of partition */
    if (winstate->grouptailpos > winstate->currentpos &&
      !are_peers(winstate, winstate->temp_slot_2,
             winstate->ss.ss_ScanTupleSlot))
      break;       /* this row is the group tail */
  }
  ExecClearTuple(winstate->temp_slot_2);
  winstate->grouptail_valid = true;

  MemoryContextSwitchTo(oldcontext);
}

/*
 * calculate_frame_offsets
 *    Determine the startOffsetValue and endOffsetValue values for the
 *    WindowAgg's frame options.
 */
static pg_noinline void
calculate_frame_offsets(PlanState *pstate)
{
  WindowAggState *winstate = castNode(WindowAggState, pstate);
  ExprContext *econtext;
  int     frameOptions = winstate->frameOptions;
  Datum   value;
  bool    isnull;
  int16   len;
  bool    byval;

  /* Ensure we've not been called before for this scan */
  Assert(winstate->all_first);

  econtext = winstate->ss.ps.ps_ExprContext;

  if (frameOptions & FRAMEOPTION_START_OFFSET)
  {
    Assert(winstate->startOffset != NULL);
    value = ExecEvalExprSwitchContext(winstate->startOffset,
                      econtext,
                      &isnull);
    if (isnull)
      ereport(ERROR,
          (errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
           errmsg("frame starting offset must not be null")));
    /* copy value into query-lifespan context */
    get_typlenbyval(exprType((Node *) winstate->startOffset->expr),
            &len,
            &byval);
    winstate->startOffsetValue = datumCopy(value, byval, len);
    if (frameOptions & (FRAMEOPTION_ROWS | FRAMEOPTION_GROUPS))
    {
      /* value is known to be int8 */
      int64   offset = DatumGetInt64(value);

      if (offset < 0)
        ereport(ERROR,
            (errcode(ERRCODE_INVALID_PRECEDING_OR_FOLLOWING_SIZE),
             errmsg("frame starting offset must not be negative")));
    }
  }

  if (frameOptions & FRAMEOPTION_END_OFFSET)
  {
    Assert(winstate->endOffset != NULL);
    value = ExecEvalExprSwitchContext(winstate->endOffset,
                      econtext,
                      &isnull);
    if (isnull)
      ereport(ERROR,
          (errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
           errmsg("frame ending offset must not be null")));
    /* copy value into query-lifespan context */
    get_typlenbyval(exprType((Node *) winstate->endOffset->expr),
            &len,
            &byval);
    winstate->endOffsetValue = datumCopy(value, byval, len);
    if (frameOptions & (FRAMEOPTION_ROWS | FRAMEOPTION_GROUPS))
    {
      /* value is known to be int8 */
      int64   offset = DatumGetInt64(value);

      if (offset < 0)
        ereport(ERROR,
            (errcode(ERRCODE_INVALID_PRECEDING_OR_FOLLOWING_SIZE),
             errmsg("frame ending offset must not be negative")));
    }
  }
  winstate->all_first = false;
}

/* -----------------
 * ExecWindowAgg
 *
 *  ExecWindowAgg receives tuples from its outer subplan and
 *  stores them into a tuplestore, then processes window functions.
 *  This node doesn't reduce nor qualify any row so the number of
 *  returned rows is exactly the same as its outer subplan's result.
 * -----------------
 */
static TupleTableSlot *
ExecWindowAgg(PlanState *pstate)
{
  WindowAggState *winstate = castNode(WindowAggState, pstate);
  TupleTableSlot *slot;
  ExprContext *econtext;
  int     i;
  int     numfuncs;

  CHECK_FOR_INTERRUPTS();

  if (winstate->status == WINDOWAGG_DONE)
    return NULL;

  /*
   * Compute frame offset values, if any, during first call (or after a
   * rescan).  These are assumed to hold constant throughout the scan; if
   * user gives us a volatile expression, we'll only use its initial value.
   */
  if (unlikely(winstate->all_first))
    calculate_frame_offsets(pstate);

  /* We need to loop as the runCondition or qual may filter out tuples */
  for (;;)
  {
    if (winstate->next_partition)
    {
      /* Initialize for first partition and set current row = 0 */
      begin_partition(winstate);
      /* If there are no input rows, we'll detect that and exit below */
    }
    else
    {
      /* Advance current row within partition */
      winstate->currentpos++;
      /* This might mean that the frame moves, too */
      winstate->framehead_valid = false;
      winstate->frametail_valid = false;
      /* we don't need to invalidate grouptail here; see below */
    }

    /*
     * Spool all tuples up to and including the current row, if we haven't
     * already
     */
    spool_tuples(winstate, winstate->currentpos);

    /* Move to the next partition if we reached the end of this partition */
    if (winstate->partition_spooled &&
      winstate->currentpos >= winstate->spooled_rows)
    {
      release_partition(winstate);

      if (winstate->more_partitions)
      {
        begin_partition(winstate);
        Assert(winstate->spooled_rows > 0);

        /* Come out of pass-through mode when changing partition */
        winstate->status = WINDOWAGG_RUN;
      }
      else
      {
        /* No further partitions?  We're done */
        winstate->status = WINDOWAGG_DONE;
        return NULL;
      }
    }

    /* final output execution is in ps_ExprContext */
    econtext = winstate->ss.ps.ps_ExprContext;

    /* Clear the per-output-tuple context for current row */
    ResetExprContext(econtext);

    /*
     * Read the current row from the tuplestore, and save in
     * ScanTupleSlot. (We can't rely on the outerplan's output slot
     * because we may have to read beyond the current row.  Also, we have
     * to actually copy the row out of the tuplestore, since window
     * function evaluation might cause the tuplestore to dump its state to
     * disk.)
     *
     * In GROUPS mode, or when tracking a group-oriented exclusion clause,
     * we must also detect entering a new peer group and update associated
     * state when that happens.  We use temp_slot_2 to temporarily hold
     * the previous row for this purpose.
     *
     * Current row must be in the tuplestore, since we spooled it above.
     */
    tuplestore_select_read_pointer(winstate->buffer, winstate->current_ptr);
    if ((winstate->frameOptions & (FRAMEOPTION_GROUPS |
                     FRAMEOPTION_EXCLUDE_GROUP |
                     FRAMEOPTION_EXCLUDE_TIES)) &&
      winstate->currentpos > 0)
    {
      ExecCopySlot(winstate->temp_slot_2, winstate->ss.ss_ScanTupleSlot);
      if (!tuplestore_gettupleslot(winstate->buffer, true, true,
                     winstate->ss.ss_ScanTupleSlot))
        elog(ERROR, "unexpected end of tuplestore");
      if (!are_peers(winstate, winstate->temp_slot_2,
               winstate->ss.ss_ScanTupleSlot))
      {
        winstate->currentgroup++;
        winstate->groupheadpos = winstate->currentpos;
        winstate->grouptail_valid = false;
      }
      ExecClearTuple(winstate->temp_slot_2);
    }
    else
    {
      if (!tuplestore_gettupleslot(winstate->buffer, true, true,
                     winstate->ss.ss_ScanTupleSlot))
        elog(ERROR, "unexpected end of tuplestore");
    }

    /* don't evaluate the window functions when we're in pass-through mode */
    if (winstate->status == WINDOWAGG_RUN)
    {
      /*
       * Evaluate true window functions
       */
      numfuncs = winstate->numfuncs;
      for (i = 0; i < numfuncs; i++)
      {
        WindowStatePerFunc perfuncstate = &(winstate->perfunc[i]);

        if (perfuncstate->plain_agg)
          continue;
        eval_windowfunction(winstate, perfuncstate,
                  &(econtext->ecxt_aggvalues[perfuncstate->wfuncstate->wfuncno]),
                  &(econtext->ecxt_aggnulls[perfuncstate->wfuncstate->wfuncno]));
      }

      /*
       * Evaluate aggregates
       */
      if (winstate->numaggs > 0)
        eval_windowaggregates(winstate);
    }

    /*
     * If we have created auxiliary read pointers for the frame or group
     * boundaries, force them to be kept up-to-date, because we don't know
     * whether the window function(s) will do anything that requires that.
     * Failing to advance the pointers would result in being unable to
     * trim data from the tuplestore, which is bad.  (If we could know in
     * advance whether the window functions will use frame boundary info,
     * we could skip creating these pointers in the first place ... but
     * unfortunately the window function API doesn't require that.)
     */
    if (winstate->framehead_ptr >= 0)
      update_frameheadpos(winstate);
    if (winstate->frametail_ptr >= 0)
      update_frametailpos(winstate);
    if (winstate->grouptail_ptr >= 0)
      update_grouptailpos(winstate);

    /*
     * Truncate any no-longer-needed rows from the tuplestore.
     */
    tuplestore_trim(winstate->buffer);

    /*
     * Form and return a projection tuple using the windowfunc results and
     * the current row.  Setting ecxt_outertuple arranges that any Vars
     * will be evaluated with respect to that row.
     */
    econtext->ecxt_outertuple = winstate->ss.ss_ScanTupleSlot;

    slot = ExecProject(winstate->ss.ps.ps_ProjInfo);

    if (winstate->status == WINDOWAGG_RUN)
    {
      econtext->ecxt_scantuple = slot;

      /*
       * Now evaluate the run condition to see if we need to go into
       * pass-through mode, or maybe stop completely.
       */
      if (!ExecQual(winstate->runcondition, econtext))
      {
        /*
         * Determine which mode to move into.  If there is no
         * PARTITION BY clause and we're the top-level WindowAgg then
         * we're done.  This tuple and any future tuples cannot
         * possibly match the runcondition.  However, when there is a
         * PARTITION BY clause or we're not the top-level window we
         * can't just stop as we need to either process other
         * partitions or ensure WindowAgg nodes above us receive all
         * of the tuples they need to process their WindowFuncs.
         */
        if (winstate->use_pass_through)
        {
          /*
           * When switching into a pass-through mode, we'd better
           * NULLify the aggregate results as these are no longer
           * updated and NULLifying them avoids the old stale
           * results lingering.  Some of these might be byref types
           * so we can't have them pointing to free'd memory.  The
           * planner insisted that quals used in the runcondition
           * are strict, so the top-level WindowAgg will always
           * filter these NULLs out in the filter clause.
           */
          numfuncs = winstate->numfuncs;
          for (i = 0; i < numfuncs; i++)
          {
            econtext->ecxt_aggvalues[i] = (Datum) 0;
            econtext->ecxt_aggnulls[i] = true;
          }

          /*
           * STRICT pass-through mode is required for the top window
           * when there is a PARTITION BY clause.  Otherwise we must
           * ensure we store tuples that don't match the
           * runcondition so they're available to WindowAggs above.
           */
          if (winstate->top_window)
          {
            winstate->status = WINDOWAGG_PASSTHROUGH_STRICT;
            continue;
          }
          else
          {
            winstate->status = WINDOWAGG_PASSTHROUGH;
          }
        }
        else
        {
          /*
           * Pass-through not required.  We can just return NULL.
           * Nothing else will match the runcondition.
           */
          winstate->status = WINDOWAGG_DONE;
          return NULL;
        }
      }

      /*
       * Filter out any tuples we don't need in the top-level WindowAgg.
       */
      if (!ExecQual(winstate->ss.ps.qual, econtext))
      {
        InstrCountFiltered1(winstate, 1);
        continue;
      }

      break;
    }

    /*
     * When not in WINDOWAGG_RUN mode, we must still return this tuple if
     * we're anything apart from the top window.
     */
    else if (!winstate->top_window)
      break;
  }

  return slot;
}

/* -----------------
 * ExecInitWindowAgg
 *
 *  Creates the run-time information for the WindowAgg node produced by the
 *  planner and initializes its outer subtree
 * -----------------
 */
WindowAggState *
ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
{
  WindowAggState *winstate;
  Plan     *outerPlan;
  ExprContext *econtext;
  ExprContext *tmpcontext;
  WindowStatePerFunc perfunc;
  WindowStatePerAgg peragg;
  int     frameOptions = node->frameOptions;
  int     numfuncs,
        wfuncno,
        numaggs,
        aggno;
  TupleDesc scanDesc;
  ListCell   *l;

  /* check for unsupported flags */
  Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));

  /*
   * create state structure
   */
  winstate = makeNode(WindowAggState);
  winstate->ss.ps.plan = (Plan *) node;
  winstate->ss.ps.state = estate;
  winstate->ss.ps.ExecProcNode = ExecWindowAgg;

  /* copy frame options to state node for easy access */
  winstate->frameOptions = frameOptions;

  /*
   * Create expression contexts.  We need two, one for per-input-tuple
   * processing and one for per-output-tuple processing.  We cheat a little
   * by using ExecAssignExprContext() to build both.
   */
  ExecAssignExprContext(estate, &winstate->ss.ps);
  tmpcontext = winstate->ss.ps.ps_ExprContext;
  winstate->tmpcontext = tmpcontext;
  ExecAssignExprContext(estate, &winstate->ss.ps);

  /* Create long-lived context for storage of partition-local memory etc */
  winstate->partcontext =
    AllocSetContextCreate(CurrentMemoryContext,
                "WindowAgg Partition",
                ALLOCSET_DEFAULT_SIZES);

  /*
   * Create mid-lived context for aggregate trans values etc.
   *
   * Note that moving aggregates each use their own private context, not
   * this one.
   */
  winstate->aggcontext =
    AllocSetContextCreate(CurrentMemoryContext,
                "WindowAgg Aggregates",
                ALLOCSET_DEFAULT_SIZES);

  /* Only the top-level WindowAgg may have a qual */
  Assert(node->plan.qual == NIL || node->topWindow);

  /* Initialize the qual */
  winstate->ss.ps.qual = ExecInitQual(node->plan.qual,
                    (PlanState *) winstate);

  /*
   * Setup the run condition, if we received one from the query planner.
   * When set, this may allow us to move into pass-through mode so that we
   * don't have to perform any further evaluation of WindowFuncs in the
   * current partition or possibly stop returning tuples altogether when all
   * tuples are in the same partition.
   */
  winstate->runcondition = ExecInitQual(node->runCondition,
                      (PlanState *) winstate);

  /*
   * When we're not the top-level WindowAgg node or we are but have a
   * PARTITION BY clause we must move into one of the WINDOWAGG_PASSTHROUGH*
   * modes when the runCondition becomes false.
   */
  winstate->use_pass_through = !node->topWindow || node->partNumCols > 0;

  /* remember if we're the top-window or we are below the top-window */
  winstate->top_window = node->topWindow;

  /*
   * initialize child nodes
   */
  outerPlan = outerPlan(node);
  outerPlanState(winstate) = ExecInitNode(outerPlan, estate, eflags);

  /*
   * initialize source tuple type (which is also the tuple type that we'll
   * store in the tuplestore and use in all our working slots).
   */
  ExecCreateScanSlotFromOuterPlan(estate, &winstate->ss, &TTSOpsMinimalTuple);
  scanDesc = winstate->ss.ss_ScanTupleSlot->tts_tupleDescriptor;

  /* the outer tuple isn't the child's tuple, but always a minimal tuple */
  winstate->ss.ps.outeropsset = true;
  winstate->ss.ps.outerops = &TTSOpsMinimalTuple;
  winstate->ss.ps.outeropsfixed = true;

  /*
   * tuple table initialization
   */
  winstate->first_part_slot = ExecInitExtraTupleSlot(estate, scanDesc,
                             &TTSOpsMinimalTuple);
  winstate->agg_row_slot = ExecInitExtraTupleSlot(estate, scanDesc,
                          &TTSOpsMinimalTuple);
  winstate->temp_slot_1 = ExecInitExtraTupleSlot(estate, scanDesc,
                           &TTSOpsMinimalTuple);
  winstate->temp_slot_2 = ExecInitExtraTupleSlot(estate, scanDesc,
                           &TTSOpsMinimalTuple);

  /*
   * create frame head and tail slots only if needed (must create slots in
   * exactly the same cases that update_frameheadpos and update_frametailpos
   * need them)
   */
  winstate->framehead_slot = winstate->frametail_slot = NULL;

  if (frameOptions & (FRAMEOPTION_RANGE | FRAMEOPTION_GROUPS))
  {
    if (((frameOptions & FRAMEOPTION_START_CURRENT_ROW) &&
       node->ordNumCols != 0) ||
      (frameOptions & FRAMEOPTION_START_OFFSET))
      winstate->framehead_slot = ExecInitExtraTupleSlot(estate, scanDesc,
                                &TTSOpsMinimalTuple);
    if (((frameOptions & FRAMEOPTION_END_CURRENT_ROW) &&
       node->ordNumCols != 0) ||
      (frameOptions & FRAMEOPTION_END_OFFSET))
      winstate->frametail_slot = ExecInitExtraTupleSlot(estate, scanDesc,
                                &TTSOpsMinimalTuple);
  }

  /*
   * Initialize result slot, type and projection.
   */
  ExecInitResultTupleSlotTL(&winstate->ss.ps, &TTSOpsVirtual);
  ExecAssignProjectionInfo(&winstate->ss.ps, NULL);

  /* Set up data for comparing tuples */
  if (node->partNumCols > 0)
    winstate->partEqfunction =
      execTuplesMatchPrepare(scanDesc,
                   node->partNumCols,
                   node->partColIdx,
                   node->partOperators,
                   node->partCollations,
                   &winstate->ss.ps);

  if (node->ordNumCols > 0)
    winstate->ordEqfunction =
      execTuplesMatchPrepare(scanDesc,
                   node->ordNumCols,
                   node->ordColIdx,
                   node->ordOperators,
                   node->ordCollations,
                   &winstate->ss.ps);

  /*
   * WindowAgg nodes use aggvalues and aggnulls as well as Agg nodes.
   */
  numfuncs = winstate->numfuncs;
  numaggs = winstate->numaggs;
  econtext = winstate->ss.ps.ps_ExprContext;
  econtext->ecxt_aggvalues = (Datum *) palloc0(sizeof(Datum) * numfuncs);
  econtext->ecxt_aggnulls = (bool *) palloc0(sizeof(bool) * numfuncs);

  /*
   * allocate per-wfunc/per-agg state information.
   */
  perfunc = (WindowStatePerFunc) palloc0(sizeof(WindowStatePerFuncData) * numfuncs);
  peragg = (WindowStatePerAgg) palloc0(sizeof(WindowStatePerAggData) * numaggs);
  winstate->perfunc = perfunc;
  winstate->peragg = peragg;

  wfuncno = -1;
  aggno = -1;
  foreach(l, winstate->funcs)
  {
    WindowFuncExprState *wfuncstate = (WindowFuncExprState *) lfirst(l);
    WindowFunc *wfunc = wfuncstate->wfunc;
    WindowStatePerFunc perfuncstate;
    AclResult aclresult;
    int     i;

    if (wfunc->winref != node->winref) /* planner screwed up? */
      elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
         wfunc->winref, node->winref);

    /* Look for a previous duplicate window function */
    for (i = 0; i <= wfuncno; i++)
    {
      if (equal(wfunc, perfunc[i].wfunc) &&
        !contain_volatile_functions((Node *) wfunc))
        break;
    }
    if (i <= wfuncno)
    {
      /* Found a match to an existing entry, so just mark it */
      wfuncstate->wfuncno = i;
      continue;
    }

    /* Nope, so assign a new PerAgg record */
    perfuncstate = &perfunc[++wfuncno];

    /* Mark WindowFunc state node with assigned index in the result array */
    wfuncstate->wfuncno = wfuncno;

    /* Check permission to call window function */
    aclresult = object_aclcheck(ProcedureRelationId, wfunc->winfnoid, GetUserId(),
                  ACL_EXECUTE);
    if (aclresult != ACLCHECK_OK)
      aclcheck_error(aclresult, OBJECT_FUNCTION,
               get_func_name(wfunc->winfnoid));
    InvokeFunctionExecuteHook(wfunc->winfnoid);

    /* Fill in the perfuncstate data */
    perfuncstate->wfuncstate = wfuncstate;
    perfuncstate->wfunc = wfunc;
    perfuncstate->numArguments = list_length(wfuncstate->args);
    perfuncstate->winCollation = wfunc->inputcollid;

    get_typlenbyval(wfunc->wintype,
            &perfuncstate->resulttypeLen,
            &perfuncstate->resulttypeByVal);

    /*
     * If it's really just a plain aggregate function, we'll emulate the
     * Agg environment for it.
     */
    perfuncstate->plain_agg = wfunc->winagg;
    if (wfunc->winagg)
    {
      WindowStatePerAgg peraggstate;

      perfuncstate->aggno = ++aggno;
      peraggstate = &winstate->peragg[aggno];
      initialize_peragg(winstate, wfunc, peraggstate);
      peraggstate->wfuncno = wfuncno;
    }
    else
    {
      WindowObject winobj = makeNode(WindowObjectData);

      winobj->winstate = winstate;
      winobj->argstates = wfuncstate->args;
      winobj->localmem = NULL;
      perfuncstate->winobj = winobj;

      /* It's a real window function, so set up to call it. */
      fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
              econtext->ecxt_per_query_memory);
      fmgr_info_set_expr((Node *) wfunc, &perfuncstate->flinfo);
    }
  }

  /* Update numfuncs, numaggs to match number of unique functions found */
  winstate->numfuncs = wfuncno + 1;
  winstate->numaggs = aggno + 1;

  /* Set up WindowObject for aggregates, if needed */
  if (winstate->numaggs > 0)
  {
    WindowObject agg_winobj = makeNode(WindowObjectData);

    agg_winobj->winstate = winstate;
    agg_winobj->argstates = NIL;
    agg_winobj->localmem = NULL;
    /* make sure markptr = -1 to invalidate. It may not get used */
    agg_winobj->markptr = -1;
    agg_winobj->readptr = -1;
    winstate->agg_winobj = agg_winobj;
  }

  /* Set the status to running */
  winstate->status = WINDOWAGG_RUN;

  /* initialize frame bound offset expressions */
  winstate->startOffset = ExecInitExpr((Expr *) node->startOffset,
                     (PlanState *) winstate);
  winstate->endOffset = ExecInitExpr((Expr *) node->endOffset,
                     (PlanState *) winstate);

  /* Lookup in_range support functions if needed */
  if (OidIsValid(node->startInRangeFunc))
    fmgr_info(node->startInRangeFunc, &winstate->startInRangeFunc);
  if (OidIsValid(node->endInRangeFunc))
    fmgr_info(node->endInRangeFunc, &winstate->endInRangeFunc);
  winstate->inRangeColl = node->inRangeColl;
  winstate->inRangeAsc = node->inRangeAsc;
  winstate->inRangeNullsFirst = node->inRangeNullsFirst;

  winstate->all_first = true;
  winstate->partition_spooled = false;
  winstate->more_partitions = false;
  winstate->next_partition = true;

  return winstate;
}

/* -----------------
 * ExecEndWindowAgg
 * -----------------
 */
void
ExecEndWindowAgg(WindowAggState *node)
{
  PlanState  *outerPlan;
  int     i;

  if (node->buffer != NULL)
  {
    tuplestore_end(node->buffer);

    /* nullify so that release_partition skips the tuplestore_clear() */
    node->buffer = NULL;
  }

  release_partition(node);

  for (i = 0; i < node->numaggs; i++)
  {
    if (node->peragg[i].aggcontext != node->aggcontext)
      MemoryContextDelete(node->peragg[i].aggcontext);
  }
  MemoryContextDelete(node->partcontext);
  MemoryContextDelete(node->aggcontext);

  pfree(node->perfunc);
  pfree(node->peragg);

  outerPlan = outerPlanState(node);
  ExecEndNode(outerPlan);
}

/* -----------------
 * ExecReScanWindowAgg
 * -----------------
 */
void
ExecReScanWindowAgg(WindowAggState *node)
{
  PlanState  *outerPlan = outerPlanState(node);
  ExprContext *econtext = node->ss.ps.ps_ExprContext;

  node->status = WINDOWAGG_RUN;
  node->all_first = true;

  /* release tuplestore et al */
  release_partition(node);

  /* release all temp tuples, but especially first_part_slot */
  ExecClearTuple(node->ss.ss_ScanTupleSlot);
  ExecClearTuple(node->first_part_slot);
  ExecClearTuple(node->agg_row_slot);
  ExecClearTuple(node->temp_slot_1);
  ExecClearTuple(node->temp_slot_2);
  if (node->framehead_slot)
    ExecClearTuple(node->framehead_slot);
  if (node->frametail_slot)
    ExecClearTuple(node->frametail_slot);

  /* Forget current wfunc values */
  MemSet(econtext->ecxt_aggvalues, 0, sizeof(Datum) * node->numfuncs);
  MemSet(econtext->ecxt_aggnulls, 0, sizeof(bool) * node->numfuncs);

  /*
   * if chgParam of subnode is not null then plan will be re-scanned by
   * first ExecProcNode.
   */
  if (outerPlan->chgParam == NULL)
    ExecReScan(outerPlan);
}

/*
 * initialize_peragg
 *
 * Almost same as in nodeAgg.c, except we don't support DISTINCT currently.
 */
static WindowStatePerAggData *
initialize_peragg(WindowAggState *winstate, WindowFunc *wfunc,
          WindowStatePerAgg peraggstate)
{
  Oid     inputTypes[FUNC_MAX_ARGS];
  int     numArguments;
  HeapTuple aggTuple;
  Form_pg_aggregate aggform;
  Oid     aggtranstype;
  AttrNumber  initvalAttNo;
  AclResult aclresult;
  bool    use_ma_code;
  Oid     transfn_oid,
        invtransfn_oid,
        finalfn_oid;
  bool    finalextra;
  char    finalmodify;
  Expr     *transfnexpr,
         *invtransfnexpr,
         *finalfnexpr;
  Datum   textInitVal;
  int     i;
  ListCell   *lc;

  numArguments = list_length(wfunc->args);

  i = 0;
  foreach(lc, wfunc->args)
  {
    inputTypes[i++] = exprType((Node *) lfirst(lc));
  }

  aggTuple = SearchSysCache1(AGGFNOID, ObjectIdGetDatum(wfunc->winfnoid));
  if (!HeapTupleIsValid(aggTuple))
    elog(ERROR, "cache lookup failed for aggregate %u",
       wfunc->winfnoid);
  aggform = (Form_pg_aggregate) GETSTRUCT(aggTuple);

  /*
   * Figure out whether we want to use the moving-aggregate implementation,
   * and collect the right set of fields from the pg_aggregate entry.
   *
   * It's possible that an aggregate would supply a safe moving-aggregate
   * implementation and an unsafe normal one, in which case our hand is
   * forced.  Otherwise, if the frame head can't move, we don't need
   * moving-aggregate code.  Even if we'd like to use it, don't do so if the
   * aggregate's arguments (and FILTER clause if any) contain any calls to
   * volatile functions.  Otherwise, the difference between restarting and
   * not restarting the aggregation would be user-visible.
   *
   * We also don't risk using moving aggregates when there are subplans in
   * the arguments or FILTER clause.  This is partly because
   * contain_volatile_functions() doesn't look inside subplans; but there
   * are other reasons why a subplan's output might be volatile.  For
   * example, syncscan mode can render the results nonrepeatable.
   */
  if (!OidIsValid(aggform->aggminvtransfn))
    use_ma_code = false; /* sine qua non */
  else if (aggform->aggmfinalmodify == AGGMODIFY_READ_ONLY &&
       aggform->aggfinalmodify != AGGMODIFY_READ_ONLY)
    use_ma_code = true;   /* decision forced by safety */
  else if (winstate->frameOptions & FRAMEOPTION_START_UNBOUNDED_PRECEDING)
    use_ma_code = false; /* non-moving frame head */
  else if (contain_volatile_functions((Node *) wfunc))
    use_ma_code = false; /* avoid possible behavioral change */
  else if (contain_subplans((Node *) wfunc))
    use_ma_code = false; /* subplans might contain volatile functions */
  else
    use_ma_code = true;   /* yes, let's use it */
  if (use_ma_code)
  {
    peraggstate->transfn_oid = transfn_oid = aggform->aggmtransfn;
    peraggstate->invtransfn_oid = invtransfn_oid = aggform->aggminvtransfn;
    peraggstate->finalfn_oid = finalfn_oid = aggform->aggmfinalfn;
    finalextra = aggform->aggmfinalextra;
    finalmodify = aggform->aggmfinalmodify;
    aggtranstype = aggform->aggmtranstype;
    initvalAttNo = Anum_pg_aggregate_aggminitval;
  }
  else
  {
    peraggstate->transfn_oid = transfn_oid = aggform->aggtransfn;
    peraggstate->invtransfn_oid = invtransfn_oid = InvalidOid;
    peraggstate->finalfn_oid = finalfn_oid = aggform->aggfinalfn;
    finalextra = aggform->aggfinalextra;
    finalmodify = aggform->aggfinalmodify;
    aggtranstype = aggform->aggtranstype;
    initvalAttNo = Anum_pg_aggregate_agginitval;
  }

  /*
   * ExecInitWindowAgg already checked permission to call aggregate function
   * ... but we still need to check the component functions
   */

  /* Check that aggregate owner has permission to call component fns */
  {
    HeapTuple procTuple;
    Oid     aggOwner;

    procTuple = SearchSysCache1(PROCOID,
                  ObjectIdGetDatum(wfunc->winfnoid));
    if (!HeapTupleIsValid(procTuple))
      elog(ERROR, "cache lookup failed for function %u",
         wfunc->winfnoid);
    aggOwner = ((Form_pg_proc) GETSTRUCT(procTuple))->proowner;
    ReleaseSysCache(procTuple);

    aclresult = object_aclcheck(ProcedureRelationId, transfn_oid, aggOwner,
                  ACL_EXECUTE);
    if (aclresult != ACLCHECK_OK)
      aclcheck_error(aclresult, OBJECT_FUNCTION,
               get_func_name(transfn_oid));
    InvokeFunctionExecuteHook(transfn_oid);

    if (OidIsValid(invtransfn_oid))
    {
      aclresult = object_aclcheck(ProcedureRelationId, invtransfn_oid, aggOwner,
                    ACL_EXECUTE);
      if (aclresult != ACLCHECK_OK)
        aclcheck_error(aclresult, OBJECT_FUNCTION,
                 get_func_name(invtransfn_oid));
      InvokeFunctionExecuteHook(invtransfn_oid);
    }

    if (OidIsValid(finalfn_oid))
    {
      aclresult = object_aclcheck(ProcedureRelationId, finalfn_oid, aggOwner,
                    ACL_EXECUTE);
      if (aclresult != ACLCHECK_OK)
        aclcheck_error(aclresult, OBJECT_FUNCTION,
                 get_func_name(finalfn_oid));
      InvokeFunctionExecuteHook(finalfn_oid);
    }
  }

  /*
   * If the selected finalfn isn't read-only, we can't run this aggregate as
   * a window function.  This is a user-facing error, so we take a bit more
   * care with the error message than elsewhere in this function.
   */
  if (finalmodify != AGGMODIFY_READ_ONLY)
    ereport(ERROR,
        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
         errmsg("aggregate function %s does not support use as a window function",
            format_procedure(wfunc->winfnoid))));

  /* Detect how many arguments to pass to the finalfn */
  if (finalextra)
    peraggstate->numFinalArgs = numArguments + 1;
  else
    peraggstate->numFinalArgs = 1;

  /* resolve actual type of transition state, if polymorphic */
  aggtranstype = resolve_aggregate_transtype(wfunc->winfnoid,
                         aggtranstype,
                         inputTypes,
                         numArguments);

  /* build expression trees using actual argument & result types */
  build_aggregate_transfn_expr(inputTypes,
                 numArguments,
                 0, /* no ordered-set window functions yet */
                 false, /* no variadic window functions yet */
                 aggtranstype,
                 wfunc->inputcollid,
                 transfn_oid,
                 invtransfn_oid,
                 &transfnexpr,
                 &invtransfnexpr);

  /* set up infrastructure for calling the transfn(s) and finalfn */
  fmgr_info(transfn_oid, &peraggstate->transfn);
  fmgr_info_set_expr((Node *) transfnexpr, &peraggstate->transfn);

  if (OidIsValid(invtransfn_oid))
  {
    fmgr_info(invtransfn_oid, &peraggstate->invtransfn);
    fmgr_info_set_expr((Node *) invtransfnexpr, &peraggstate->invtransfn);
  }

  if (OidIsValid(finalfn_oid))
  {
    build_aggregate_finalfn_expr(inputTypes,
                   peraggstate->numFinalArgs,
                   aggtranstype,
                   wfunc->wintype,
                   wfunc->inputcollid,
                   finalfn_oid,
                   &finalfnexpr);
    fmgr_info(finalfn_oid, &peraggstate->finalfn);
    fmgr_info_set_expr((Node *) finalfnexpr, &peraggstate->finalfn);
  }

  /* get info about relevant datatypes */
  get_typlenbyval(wfunc->wintype,
          &peraggstate->resulttypeLen,
          &peraggstate->resulttypeByVal);
  get_typlenbyval(aggtranstype,
          &peraggstate->transtypeLen,
          &peraggstate->transtypeByVal);

  /*
   * initval is potentially null, so don't try to access it as a struct
   * field. Must do it the hard way with SysCacheGetAttr.
   */
  textInitVal = SysCacheGetAttr(AGGFNOID, aggTuple, initvalAttNo,
                  &peraggstate->initValueIsNull);

  if (peraggstate->initValueIsNull)
    peraggstate->initValue = (Datum) 0;
  else
    peraggstate->initValue = GetAggInitVal(textInitVal,
                         aggtranstype);

  /*
   * If the transfn is strict and the initval is NULL, make sure input type
   * and transtype are the same (or at least binary-compatible), so that
   * it's OK to use the first input value as the initial transValue.  This
   * should have been checked at agg definition time, but we must check
   * again in case the transfn's strictness property has been changed.
   */
  if (peraggstate->transfn.fn_strict && peraggstate->initValueIsNull)
  {
    if (numArguments < 1 ||
      !IsBinaryCoercible(inputTypes[0], aggtranstype))
      ereport(ERROR,
          (errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
           errmsg("aggregate %u needs to have compatible input type and transition type",
              wfunc->winfnoid)));
  }

  /*
   * Insist that forward and inverse transition functions have the same
   * strictness setting.  Allowing them to differ would require handling
   * more special cases in advance_windowaggregate and
   * advance_windowaggregate_base, for no discernible benefit.  This should
   * have been checked at agg definition time, but we must check again in
   * case either function's strictness property has been changed.
   */
  if (OidIsValid(invtransfn_oid) &&
    peraggstate->transfn.fn_strict != peraggstate->invtransfn.fn_strict)
    ereport(ERROR,
        (errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
         errmsg("strictness of aggregate's forward and inverse transition functions must match")));

  /*
   * Moving aggregates use their own aggcontext.
   *
   * This is necessary because they might restart at different times, so we
   * might never be able to reset the shared context otherwise.  We can't
   * make it the aggregates' responsibility to clean up after themselves,
   * because strict aggregates must be restarted whenever we remove their
   * last non-NULL input, which the aggregate won't be aware is happening.
   * Also, just pfree()ing the transValue upon restarting wouldn't help,
   * since we'd miss any indirectly referenced data.  We could, in theory,
   * make the memory allocation rules for moving aggregates different than
   * they have historically been for plain aggregates, but that seems grotty
   * and likely to lead to memory leaks.
   */
  if (OidIsValid(invtransfn_oid))
    peraggstate->aggcontext =
      AllocSetContextCreate(CurrentMemoryContext,
                  "WindowAgg Per Aggregate",
                  ALLOCSET_DEFAULT_SIZES);
  else
    peraggstate->aggcontext = winstate->aggcontext;

  ReleaseSysCache(aggTuple);

  return peraggstate;
}

static Datum
GetAggInitVal(Datum textInitVal, Oid transtype)
{
  Oid     typinput,
        typioparam;
  char     *strInitVal;
  Datum   initVal;

  getTypeInputInfo(transtype, &typinput, &typioparam);
  strInitVal = TextDatumGetCString(textInitVal);
  initVal = OidInputFunctionCall(typinput, strInitVal,
                   typioparam, -1);
  pfree(strInitVal);
  return initVal;
}

/*
 * are_peers
 * compare two rows to see if they are equal according to the ORDER BY clause
 *
 * NB: this does not consider the window frame mode.
 */
static bool
are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
      TupleTableSlot *slot2)
{
  WindowAgg  *node = (WindowAgg *) winstate->ss.ps.plan;
  ExprContext *econtext = winstate->tmpcontext;

  /* If no ORDER BY, all rows are peers with each other */
  if (node->ordNumCols == 0)
    return true;

  econtext->ecxt_outertuple = slot1;
  econtext->ecxt_innertuple = slot2;
  return ExecQualAndReset(winstate->ordEqfunction, econtext);
}

/*
 * window_gettupleslot
 *  Fetch the pos'th tuple of the current partition into the slot,
 *  using the winobj's read pointer
 *
 * Returns true if successful, false if no such row
 */
static bool
window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
{
  WindowAggState *winstate = winobj->winstate;
  MemoryContext oldcontext;

  /* often called repeatedly in a row */
  CHECK_FOR_INTERRUPTS();

  /* Don't allow passing -1 to spool_tuples here */
  if (pos < 0)
    return false;

  /* If necessary, fetch the tuple into the spool */
  spool_tuples(winstate, pos);

  if (pos >= winstate->spooled_rows)
    return false;

  if (pos < winobj->markpos)
    elog(ERROR, "cannot fetch row before WindowObject's mark position");

  oldcontext = MemoryContextSwitchTo(winstate->ss.ps.ps_ExprContext->ecxt_per_query_memory);

  tuplestore_select_read_pointer(winstate->buffer, winobj->readptr);

  /*
   * Advance or rewind until we are within one tuple of the one we want.
   */
  if (winobj->seekpos < pos - 1)
  {
    if (!tuplestore_skiptuples(winstate->buffer,
                   pos - 1 - winobj->seekpos,
                   true))
      elog(ERROR, "unexpected end of tuplestore");
    winobj->seekpos = pos - 1;
  }
  else if (winobj->seekpos > pos + 1)
  {
    if (!tuplestore_skiptuples(winstate->buffer,
                   winobj->seekpos - (pos + 1),
                   false))
      elog(ERROR, "unexpected end of tuplestore");
    winobj->seekpos = pos + 1;
  }
  else if (winobj->seekpos == pos)
  {
    /*
     * There's no API to refetch the tuple at the current position.  We
     * have to move one tuple forward, and then one backward.  (We don't
     * do it the other way because we might try to fetch the row before
     * our mark, which isn't allowed.)  XXX this case could stand to be
     * optimized.
     */
    tuplestore_advance(winstate->buffer, true);
    winobj->seekpos++;
  }

  /*
   * Now we should be on the tuple immediately before or after the one we
   * want, so just fetch forwards or backwards as appropriate.
   *
   * Notice that we tell tuplestore_gettupleslot to make a physical copy of
   * the fetched tuple.  This ensures that the slot's contents remain valid
   * through manipulations of the tuplestore, which some callers depend on.
   */
  if (winobj->seekpos > pos)
  {
    if (!tuplestore_gettupleslot(winstate->buffer, false, true, slot))
      elog(ERROR, "unexpected end of tuplestore");
    winobj->seekpos--;
  }
  else
  {
    if (!tuplestore_gettupleslot(winstate->buffer, true, true, slot))
      elog(ERROR, "unexpected end of tuplestore");
    winobj->seekpos++;
  }

  Assert(winobj->seekpos == pos);

  MemoryContextSwitchTo(oldcontext);

  return true;
}


/***********************************************************************
 * API exposed to window functions
 ***********************************************************************/


/*
 * WinGetPartitionLocalMemory
 *    Get working memory that lives till end of partition processing
 *
 * On first call within a given partition, this allocates and zeroes the
 * requested amount of space.  Subsequent calls just return the same chunk.
 *
 * Memory obtained this way is normally used to hold state that should be
 * automatically reset for each new partition.  If a window function wants
 * to hold state across the whole query, fcinfo->fn_extra can be used in the
 * usual way for that.
 */
void *
WinGetPartitionLocalMemory(WindowObject winobj, Size sz)
{
  Assert(WindowObjectIsValid(winobj));
  if (winobj->localmem == NULL)
    winobj->localmem =
      MemoryContextAllocZero(winobj->winstate->partcontext, sz);
  return winobj->localmem;
}

/*
 * WinGetCurrentPosition
 *    Return the current row's position (counting from 0) within the current
 *    partition.
 */
int64
WinGetCurrentPosition(WindowObject winobj)
{
  Assert(WindowObjectIsValid(winobj));
  return winobj->winstate->currentpos;
}

/*
 * WinGetPartitionRowCount
 *    Return total number of rows contained in the current partition.
 *
 * Note: this is a relatively expensive operation because it forces the
 * whole partition to be "spooled" into the tuplestore at once.  Once
 * executed, however, additional calls within the same partition are cheap.
 */
int64
WinGetPartitionRowCount(WindowObject winobj)
{
  Assert(WindowObjectIsValid(winobj));
  spool_tuples(winobj->winstate, -1);
  return winobj->winstate->spooled_rows;
}

/*
 * WinSetMarkPosition
 *    Set the "mark" position for the window object, which is the oldest row
 *    number (counting from 0) it is allowed to fetch during all subsequent
 *    operations within the current partition.
 *
 * Window functions do not have to call this, but are encouraged to move the
 * mark forward when possible to keep the tuplestore size down and prevent
 * having to spill rows to disk.
 */
void
WinSetMarkPosition(WindowObject winobj, int64 markpos)
{
  WindowAggState *winstate;

  Assert(WindowObjectIsValid(winobj));
  winstate = winobj->winstate;

  if (markpos < winobj->markpos)
    elog(ERROR, "cannot move WindowObject's mark position backward");
  tuplestore_select_read_pointer(winstate->buffer, winobj->markptr);
  if (markpos > winobj->markpos)
  {
    tuplestore_skiptuples(winstate->buffer,
                markpos - winobj->markpos,
                true);
    winobj->markpos = markpos;
  }
  tuplestore_select_read_pointer(winstate->buffer, winobj->readptr);
  if (markpos > winobj->seekpos)
  {
    tuplestore_skiptuples(winstate->buffer,
                markpos - winobj->seekpos,
                true);
    winobj->seekpos = markpos;
  }
}

/*
 * WinRowsArePeers
 *    Compare two rows (specified by absolute position in partition) to see
 *    if they are equal according to the ORDER BY clause.
 *
 * NB: this does not consider the window frame mode.
 */
bool
WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2)
{
  WindowAggState *winstate;
  WindowAgg  *node;
  TupleTableSlot *slot1;
  TupleTableSlot *slot2;
  bool    res;

  Assert(WindowObjectIsValid(winobj));
  winstate = winobj->winstate;
  node = (WindowAgg *) winstate->ss.ps.plan;

  /* If no ORDER BY, all rows are peers; don't bother to fetch them */
  if (node->ordNumCols == 0)
    return true;

  /*
   * Note: OK to use temp_slot_2 here because we aren't calling any
   * frame-related functions (those tend to clobber temp_slot_2).
   */
  slot1 = winstate->temp_slot_1;
  slot2 = winstate->temp_slot_2;

  if (!window_gettupleslot(winobj, pos1, slot1))
    elog(ERROR, "specified position is out of window: " INT64_FORMAT,
       pos1);
  if (!window_gettupleslot(winobj, pos2, slot2))
    elog(ERROR, "specified position is out of window: " INT64_FORMAT,
       pos2);

  res = are_peers(winstate, slot1, slot2);

  ExecClearTuple(slot1);
  ExecClearTuple(slot2);

  return res;
}

/*
 * WinGetFuncArgInPartition
 *    Evaluate a window function's argument expression on a specified
 *    row of the partition.  The row is identified in lseek(2) style,
 *    i.e. relative to the current, first, or last row.
 *
 * argno: argument number to evaluate (counted from 0)
 * relpos: signed rowcount offset from the seek position
 * seektype: WINDOW_SEEK_CURRENT, WINDOW_SEEK_HEAD, or WINDOW_SEEK_TAIL
 * set_mark: If the row is found and set_mark is true, the mark is moved to
 *    the row as a side-effect.
 * isnull: output argument, receives isnull status of result
 * isout: output argument, set to indicate whether target row position
 *    is out of partition (can pass NULL if caller doesn't care about this)
 *
 * Specifying a nonexistent row is not an error, it just causes a null result
 * (plus setting *isout true, if isout isn't NULL).
 */
Datum
WinGetFuncArgInPartition(WindowObject winobj, int argno,
             int relpos, int seektype, bool set_mark,
             bool *isnull, bool *isout)
{
  WindowAggState *winstate;
  ExprContext *econtext;
  TupleTableSlot *slot;
  bool    gottuple;
  int64   abs_pos;

  Assert(WindowObjectIsValid(winobj));
  winstate = winobj->winstate;
  econtext = winstate->ss.ps.ps_ExprContext;
  slot = winstate->temp_slot_1;

  switch (seektype)
  {
    case WINDOW_SEEK_CURRENT:
      abs_pos = winstate->currentpos + relpos;
      break;
    case WINDOW_SEEK_HEAD:
      abs_pos = relpos;
      break;
    case WINDOW_SEEK_TAIL:
      spool_tuples(winstate, -1);
      abs_pos = winstate->spooled_rows - 1 + relpos;
      break;
    default:
      elog(ERROR, "unrecognized window seek type: %d", seektype);
      abs_pos = 0;    /* keep compiler quiet */
      break;
  }

  gottuple = window_gettupleslot(winobj, abs_pos, slot);

  if (!gottuple)
  {
    if (isout)
      *isout = true;
    *isnull = true;
    return (Datum) 0;
  }
  else
  {
    if (isout)
      *isout = false;
    if (set_mark)
      WinSetMarkPosition(winobj, abs_pos);
    econtext->ecxt_outertuple = slot;
    return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
              econtext, isnull);
  }
}

/*
 * WinGetFuncArgInFrame
 *    Evaluate a window function's argument expression on a specified
 *    row of the window frame.  The row is identified in lseek(2) style,
 *    i.e. relative to the first or last row of the frame.  (We do not
 *    support WINDOW_SEEK_CURRENT here, because it's not very clear what
 *    that should mean if the current row isn't part of the frame.)
 *
 * argno: argument number to evaluate (counted from 0)
 * relpos: signed rowcount offset from the seek position
 * seektype: WINDOW_SEEK_HEAD or WINDOW_SEEK_TAIL
 * set_mark: If the row is found/in frame and set_mark is true, the mark is
 *    moved to the row as a side-effect.
 * isnull: output argument, receives isnull status of result
 * isout: output argument, set to indicate whether target row position
 *    is out of frame (can pass NULL if caller doesn't care about this)
 *
 * Specifying a nonexistent or not-in-frame row is not an error, it just
 * causes a null result (plus setting *isout true, if isout isn't NULL).
 *
 * Note that some exclusion-clause options lead to situations where the
 * rows that are in-frame are not consecutive in the partition.  But we
 * count only in-frame rows when measuring relpos.
 *
 * The set_mark flag is interpreted as meaning that the caller will specify
 * a constant (or, perhaps, monotonically increasing) relpos in successive
 * calls, so that *if there is no exclusion clause* there will be no need
 * to fetch a row before the previously fetched row.  But we do not expect
 * the caller to know how to account for exclusion clauses.  Therefore,
 * if there is an exclusion clause we take responsibility for adjusting the
 * mark request to something that will be safe given the above assumption
 * about relpos.
 */
Datum
WinGetFuncArgInFrame(WindowObject winobj, int argno,
           int relpos, int seektype, bool set_mark,
           bool *isnull, bool *isout)
{
  WindowAggState *winstate;
  ExprContext *econtext;
  TupleTableSlot *slot;
  int64   abs_pos;
  int64   mark_pos;

  Assert(WindowObjectIsValid(winobj));
  winstate = winobj->winstate;
  econtext = winstate->ss.ps.ps_ExprContext;
  slot = winstate->temp_slot_1;

  switch (seektype)
  {
    case WINDOW_SEEK_CURRENT:
      elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
      abs_pos = mark_pos = 0; /* keep compiler quiet */
      break;
    case WINDOW_SEEK_HEAD:
      /* rejecting relpos < 0 is easy and simplifies code below */
      if (relpos < 0)
        goto out_of_frame;
      update_frameheadpos(winstate);
      abs_pos = winstate->frameheadpos + relpos;
      mark_pos = abs_pos;

      /*
       * Account for exclusion option if one is active, but advance only
       * abs_pos not mark_pos.  This prevents changes of the current
       * row's peer group from resulting in trying to fetch a row before
       * some previous mark position.
       *
       * Note that in some corner cases such as current row being
       * outside frame, these calculations are theoretically too simple,
       * but it doesn't matter because we'll end up deciding the row is
       * out of frame.  We do not attempt to avoid fetching rows past
       * end of frame; that would happen in some cases anyway.
       */
      switch (winstate->frameOptions & FRAMEOPTION_EXCLUSION)
      {
        case 0:
          /* no adjustment needed */
          break;
        case FRAMEOPTION_EXCLUDE_CURRENT_ROW:
          if (abs_pos >= winstate->currentpos &&
            winstate->currentpos >= winstate->frameheadpos)
            abs_pos++;
          break;
        case FRAMEOPTION_EXCLUDE_GROUP:
          update_grouptailpos(winstate);
          if (abs_pos >= winstate->groupheadpos &&
            winstate->grouptailpos > winstate->frameheadpos)
          {
            int64   overlapstart = Max(winstate->groupheadpos,
                             winstate->frameheadpos);

            abs_pos += winstate->grouptailpos - overlapstart;
          }
          break;
        case FRAMEOPTION_EXCLUDE_TIES:
          update_grouptailpos(winstate);
          if (abs_pos >= winstate->groupheadpos &&
            winstate->grouptailpos > winstate->frameheadpos)
          {
            int64   overlapstart = Max(winstate->groupheadpos,
                             winstate->frameheadpos);

            if (abs_pos == overlapstart)
              abs_pos = winstate->currentpos;
            else
              abs_pos += winstate->grouptailpos - overlapstart - 1;
          }
          break;
        default:
          elog(ERROR, "unrecognized frame option state: 0x%x",
             winstate->frameOptions);
          break;
      }
      break;
    case WINDOW_SEEK_TAIL:
      /* rejecting relpos > 0 is easy and simplifies code below */
      if (relpos > 0)
        goto out_of_frame;
      update_frametailpos(winstate);
      abs_pos = winstate->frametailpos - 1 + relpos;

      /*
       * Account for exclusion option if one is active.  If there is no
       * exclusion, we can safely set the mark at the accessed row.  But
       * if there is, we can only mark the frame start, because we can't
       * be sure how far back in the frame the exclusion might cause us
       * to fetch in future.  Furthermore, we have to actually check
       * against frameheadpos here, since it's unsafe to try to fetch a
       * row before frame start if the mark might be there already.
       */
      switch (winstate->frameOptions & FRAMEOPTION_EXCLUSION)
      {
        case 0:
          /* no adjustment needed */
          mark_pos = abs_pos;
          break;
        case FRAMEOPTION_EXCLUDE_CURRENT_ROW:
          if (abs_pos <= winstate->currentpos &&
            winstate->currentpos < winstate->frametailpos)
            abs_pos--;
          update_frameheadpos(winstate);
          if (abs_pos < winstate->frameheadpos)
            goto out_of_frame;
          mark_pos = winstate->frameheadpos;
          break;
        case FRAMEOPTION_EXCLUDE_GROUP:
          update_grouptailpos(winstate);
          if (abs_pos < winstate->grouptailpos &&
            winstate->groupheadpos < winstate->frametailpos)
          {
            int64   overlapend = Min(winstate->grouptailpos,
                           winstate->frametailpos);

            abs_pos -= overlapend - winstate->groupheadpos;
          }
          update_frameheadpos(winstate);
          if (abs_pos < winstate->frameheadpos)
            goto out_of_frame;
          mark_pos = winstate->frameheadpos;
          break;
        case FRAMEOPTION_EXCLUDE_TIES:
          update_grouptailpos(winstate);
          if (abs_pos < winstate->grouptailpos &&
            winstate->groupheadpos < winstate->frametailpos)
          {
            int64   overlapend = Min(winstate->grouptailpos,
                           winstate->frametailpos);

            if (abs_pos == overlapend - 1)
              abs_pos = winstate->currentpos;
            else
              abs_pos -= overlapend - 1 - winstate->groupheadpos;
          }
          update_frameheadpos(winstate);
          if (abs_pos < winstate->frameheadpos)
            goto out_of_frame;
          mark_pos = winstate->frameheadpos;
          break;
        default:
          elog(ERROR, "unrecognized frame option state: 0x%x",
             winstate->frameOptions);
          mark_pos = 0; /* keep compiler quiet */
          break;
      }
      break;
    default:
      elog(ERROR, "unrecognized window seek type: %d", seektype);
      abs_pos = mark_pos = 0; /* keep compiler quiet */
      break;
  }

  if (!window_gettupleslot(winobj, abs_pos, slot))
    goto out_of_frame;

  /* The code above does not detect all out-of-frame cases, so check */
  if (row_is_in_frame(winstate, abs_pos, slot) <= 0)
    goto out_of_frame;

  if (isout)
    *isout = false;
  if (set_mark)
    WinSetMarkPosition(winobj, mark_pos);
  econtext->ecxt_outertuple = slot;
  return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
            econtext, isnull);

out_of_frame:
  if (isout)
    *isout = true;
  *isnull = true;
  return (Datum) 0;
}

/*
 * WinGetFuncArgCurrent
 *    Evaluate a window function's argument expression on the current row.
 *
 * argno: argument number to evaluate (counted from 0)
 * isnull: output argument, receives isnull status of result
 *
 * Note: this isn't quite equivalent to WinGetFuncArgInPartition or
 * WinGetFuncArgInFrame targeting the current row, because it will succeed
 * even if the WindowObject's mark has been set beyond the current row.
 * This should generally be used for "ordinary" arguments of a window
 * function, such as the offset argument of lead() or lag().
 */
Datum
WinGetFuncArgCurrent(WindowObject winobj, int argno, bool *isnull)
{
  WindowAggState *winstate;
  ExprContext *econtext;

  Assert(WindowObjectIsValid(winobj));
  winstate = winobj->winstate;

  econtext = winstate->ss.ps.ps_ExprContext;

  econtext->ecxt_outertuple = winstate->ss.ss_ScanTupleSlot;
  return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
            econtext, isnull);
}

Coverage Report

Created: 2025-07-03 06:49