/*-------------------------------------------------------------------------

 *

 * indexam.c

 *    general index access method routines

 *

 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group

 * Portions Copyright (c) 1994, Regents of the University of California

 *

 *

 * IDENTIFICATION

 *    src/backend/access/index/indexam.c

 *

 * INTERFACE ROUTINES

 *    index_open    - open an index relation by relation OID

 *    index_close   - close an index relation

 *    index_beginscan - start a scan of an index with amgettuple

 *    index_beginscan_bitmap - start a scan of an index with amgetbitmap

 *    index_rescan  - restart a scan of an index

 *    index_endscan - end a scan

 *    index_insert  - insert an index tuple into a relation

 *    index_markpos - mark a scan position

 *    index_restrpos  - restore a scan position

 *    index_parallelscan_estimate - estimate shared memory for parallel scan

 *    index_parallelscan_initialize - initialize parallel scan

 *    index_parallelrescan  - (re)start a parallel scan of an index

 *    index_beginscan_parallel - join parallel index scan

 *    index_getbitmap - get all tuples from a scan

 *    index_bulk_delete - bulk deletion of index tuples

 *    index_vacuum_cleanup  - post-deletion cleanup of an index

 *    index_can_return  - does index support index-only scans?

 *    index_getprocid - get a support procedure OID

 *    index_getprocinfo - get a support procedure's lookup info

 *

 * NOTES

 *    This file contains the index_ routines which used

 *    to be a scattered collection of stuff in access/genam.

 *

 *-------------------------------------------------------------------------

 */

#include "postgres.h"

#include "access/amapi.h"

#include "access/relation.h"

#include "access/reloptions.h"

#include "access/relscan.h"

#include "access/tableam.h"

#include "catalog/index.h"

#include "catalog/pg_type.h"

#include "nodes/execnodes.h"

#include "pgstat.h"

#include "storage/lmgr.h"

#include "storage/lock.h"

#include "storage/predicate.h"

#include "utils/ruleutils.h"

#include "utils/snapmgr.h"

#include "utils/syscache.h"

/* ----------------------------------------------------------------

 *          macros used in index_ routines

 *

 * Note: the ReindexIsProcessingIndex() check in RELATION_CHECKS is there

 * to check that we don't try to scan or do retail insertions into an index

 * that is currently being rebuilt or pending rebuild.  This helps to catch

 * things that don't work when reindexing system catalogs, as well as prevent

 * user errors like index expressions that access their own tables.  The check

 * doesn't prevent the actual rebuild because we don't use RELATION_CHECKS

 * when calling the index AM's ambuild routine, and there is no reason for

 * ambuild to call its subsidiary routines through this file.

 * ----------------------------------------------------------------

 */

#define RELATION_CHECKS \

do { \

  Assert(RelationIsValid(indexRelation)); \

  Assert(indexRelation->rd_indam); \

  if (unlikely(ReindexIsProcessingIndex(RelationGetRelid(indexRelation)))) \

    ereport(ERROR, \

        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), \

         errmsg("cannot access index \"%s\" while it is being reindexed", \

            RelationGetRelationName(indexRelation)))); \

} while(0)

#define SCAN_CHECKS \

( \

  AssertMacro(scan), \

  AssertMacro(RelationIsValid(scan->indexRelation)), \

  AssertMacro(scan->indexRelation->rd_indam) \

)

#define CHECK_REL_PROCEDURE(pname) \

do { \

  if (indexRelation->rd_indam->pname == NULL) \

    elog(ERROR, "function \"%s\" is not defined for index \"%s\"", \

       CppAsString(pname), RelationGetRelationName(indexRelation)); \

} while(0)

#define CHECK_SCAN_PROCEDURE(pname) \

do { \

  if (scan->indexRelation->rd_indam->pname == NULL) \

    elog(ERROR, "function \"%s\" is not defined for index \"%s\"", \

       CppAsString(pname), RelationGetRelationName(scan->indexRelation)); \

} while(0)

static inline void validate_relation_as_index(Relation r);

static pg_always_inline IndexScanDesc index_beginscan_internal(Relation indexRelation,

                                 Relation heapRelation,

                                 int nkeys,

                                 int norderbys,

                                 Snapshot snapshot,

                                 ParallelIndexScanDesc pscan,

                                 IndexScanInstrumentation *instrument,

                                 bool index_only_scan,

                                 bool temp_snap,

                                 uint32 flags);

/* ----------------------------------------------------------------

 *           index_ interface functions

 * ----------------------------------------------------------------

 */

/* ----------------

 *    index_open - open an index relation by relation OID

 *

 *    If lockmode is not "NoLock", the specified kind of lock is

 *    obtained on the index.  (Generally, NoLock should only be

 *    used if the caller knows it has some appropriate lock on the

 *    index already.)

 *

 *    An error is raised if the index does not exist.

 *

 *    This is a convenience routine adapted for indexscan use.

 *    Some callers may prefer to use relation_open directly.

 * ----------------

 */

Relation

index_open(Oid relationId, LOCKMODE lockmode)

{

  Relation  r;

  r = relation_open(relationId, lockmode);

  validate_relation_as_index(r);

  return r;

}

/* ----------------

 *    try_index_open - open an index relation by relation OID

 *

 *    Same as index_open, except return NULL instead of failing

 *    if the relation does not exist.

 * ----------------

 */

Relation

try_index_open(Oid relationId, LOCKMODE lockmode)

{

  Relation  r;

  r = try_relation_open(relationId, lockmode);

  /* leave if index does not exist */

  if (!r)

    return NULL;

  validate_relation_as_index(r);

  return r;

}

/* ----------------

 *    index_close - close an index relation

 *

 *    If lockmode is not "NoLock", we then release the specified lock.

 *

 *    Note that it is often sensible to hold a lock beyond index_close;

 *    in that case, the lock is released automatically at xact end.

 * ----------------

 */

void

index_close(Relation relation, LOCKMODE lockmode)

{

  LockRelId relid = relation->rd_lockInfo.lockRelId;

  Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES);

  /* The relcache does the real work... */

  RelationClose(relation);

  if (lockmode != NoLock)

    UnlockRelationId(&relid, lockmode);

}

/* ----------------

 *    validate_relation_as_index

 *

 *    Make sure relkind is an index or a partitioned index.

 * ----------------

 */

static inline void

validate_relation_as_index(Relation r)

{

  if (r->rd_rel->relkind != RELKIND_INDEX &&

    r->rd_rel->relkind != RELKIND_PARTITIONED_INDEX)

    ereport(ERROR,

        (errcode(ERRCODE_WRONG_OBJECT_TYPE),

         errmsg("\"%s\" is not an index",

            RelationGetRelationName(r))));

}

/* ----------------

 *    index_insert - insert an index tuple into a relation

 * ----------------

 */

bool

index_insert(Relation indexRelation,

       Datum *values,

       bool *isnull,

       ItemPointer heap_t_ctid,

       Relation heapRelation,

       IndexUniqueCheck checkUnique,

       bool indexUnchanged,

       IndexInfo *indexInfo)

{

  RELATION_CHECKS;

  CHECK_REL_PROCEDURE(aminsert);

  if (!(indexRelation->rd_indam->ampredlocks))

    CheckForSerializableConflictIn(indexRelation,

                     (ItemPointer) NULL,

                     InvalidBlockNumber);

  return indexRelation->rd_indam->aminsert(indexRelation, values, isnull,

                       heap_t_ctid, heapRelation,

                       checkUnique, indexUnchanged,

                       indexInfo);

}

/* -------------------------

 *    index_insert_cleanup - clean up after all index inserts are done

 * -------------------------

 */

void

index_insert_cleanup(Relation indexRelation,

           IndexInfo *indexInfo)

{

  RELATION_CHECKS;

  if (indexRelation->rd_indam->aminsertcleanup)

    indexRelation->rd_indam->aminsertcleanup(indexRelation, indexInfo);

}

/*

 * index_beginscan - start a scan of an index with amgettuple

 *

 * Caller must be holding suitable locks on the heap and the index.

 */

IndexScanDesc

index_beginscan(Relation heapRelation,

        Relation indexRelation,

        bool index_only_scan,

        Snapshot snapshot,

        IndexScanInstrumentation *instrument,

        int nkeys, int norderbys,

        uint32 flags)

{

  Assert(snapshot != InvalidSnapshot);

  pg_assume(heapRelation != NULL);

  /* Check that a historic snapshot is not used for non-catalog tables */

  if (IsHistoricMVCCSnapshot(snapshot) &&

    !RelationIsAccessibleInLogicalDecoding(heapRelation))

  {

    ereport(ERROR,

        (errcode(ERRCODE_INVALID_TRANSACTION_STATE),

         errmsg("cannot query non-catalog table \"%s\" during logical decoding",

            RelationGetRelationName(heapRelation))));

  }

  return index_beginscan_internal(indexRelation, heapRelation,

                  nkeys, norderbys,

                  snapshot, NULL, instrument,

                  index_only_scan, false, flags);

}

/*

 * index_beginscan_bitmap - start a scan of an index with amgetbitmap

 *

 * As above, caller had better be holding some lock on the parent heap

 * relation, even though it's not explicitly mentioned here.

 */

IndexScanDesc

index_beginscan_bitmap(Relation indexRelation,

             Snapshot snapshot,

             IndexScanInstrumentation *instrument,

             int nkeys)

{

  Assert(snapshot != InvalidSnapshot);

  Assert(IsMVCCLikeSnapshot(snapshot));

  return index_beginscan_internal(indexRelation, NULL, nkeys, 0, snapshot,

                  NULL, instrument, false, false, SO_NONE);

}

/*

 * index_beginscan_internal --- common code for index_beginscan variants

 *

 * When heapRelation is not NULL, also initializes table AM index scan state.

 */

static pg_always_inline IndexScanDesc

index_beginscan_internal(Relation indexRelation, Relation heapRelation,

             int nkeys, int norderbys, Snapshot snapshot,

             ParallelIndexScanDesc pscan,

             IndexScanInstrumentation *instrument,

             bool index_only_scan, bool temp_snap, uint32 flags)

{

  IndexScanDesc scan;

  RELATION_CHECKS;

  CHECK_REL_PROCEDURE(ambeginscan);

  if (!(indexRelation->rd_indam->ampredlocks))

    PredicateLockRelation(indexRelation, snapshot);

  /*

   * We hold a reference count to the relcache entry throughout the scan.

   */

  RelationIncrementReferenceCount(indexRelation);

  /*

   * Tell the AM to open a scan.

   */

  scan = indexRelation->rd_indam->ambeginscan(indexRelation, nkeys,

                        norderbys);

  /* Initialize information for parallel scan. */

  scan->parallel_scan = pscan;

  scan->xs_temp_snap = temp_snap;

  scan->xs_snapshot = snapshot;

  scan->instrument = instrument;

  /*

   * Initialize heap-side scan state when a heap relation is provided.

   * Bitmap index scans don't provide one.

   */

  if (heapRelation != NULL)

  {

    scan->heapRelation = heapRelation;

    scan->xs_want_itup = index_only_scan;

    scan->xs_heap_continue = false;

    /*

     * The "name" type's btree opclass stores index keys as cstrings

     * rather than names to save space, so keys returned by an index-only

     * scan must be re-padded to NAMEDATALEN allocations.  Set up the

     * state tableam_index_fill_ios_slot uses to do that.  We detect such

     * columns generically (stored type CSTRINGOID, opclass input type

     * NAMEOID) in case other opclasses adopt the same optimization.

     */

    if (index_only_scan)

    {

      int     indnkeyatts = indexRelation->rd_index->indnkeyatts;

      int     namecount = 0;

      for (int attnum = 0; attnum < indnkeyatts; attnum++)

      {

        if (TupleDescAttr(indexRelation->rd_att, attnum)->atttypid == CSTRINGOID &&

          indexRelation->rd_opcintype[attnum] == NAMEOID)

          namecount++;

      }

      if (unlikely(namecount > 0))

      {

        int     idx = 0;

        scan->xs_name_cstring_attnums = palloc_array(AttrNumber, namecount);

        for (int attnum = 0; attnum < indnkeyatts; attnum++)

        {

          if (TupleDescAttr(indexRelation->rd_att, attnum)->atttypid == CSTRINGOID &&

            indexRelation->rd_opcintype[attnum] == NAMEOID)

            scan->xs_name_cstring_attnums[idx++] = (AttrNumber) attnum;

        }

        scan->xs_name_cstring_buf = palloc(namecount * NAMEDATALEN);

        scan->xs_name_cstring_count = namecount;

      }

    }

    /* set up table AM state for the index scan (sets xs_table_opaque) */

    table_index_scan_begin(scan, flags);

    /* table AM must set these for us */

    Assert(scan->xs_getnext_slot != NULL && scan->xs_table_opaque != NULL);

  }

  return scan;

}

/* ----------------

 *    index_rescan  - (re)start a scan of an index

 *

 * During a restart, the caller may specify a new set of scankeys and/or

 * orderbykeys; but the number of keys cannot differ from what index_beginscan

 * was told.  (Later we might relax that to "must not exceed", but currently

 * the index AMs tend to assume that scan->numberOfKeys is what to believe.)

 * To restart the scan without changing keys, pass NULL for the key arrays.

 * (Of course, keys *must* be passed on the first call, unless

 * scan->numberOfKeys is zero.)

 * ----------------

 */

void

index_rescan(IndexScanDesc scan,

       ScanKey keys, int nkeys,

       ScanKey orderbys, int norderbys)

{

  SCAN_CHECKS;

  CHECK_SCAN_PROCEDURE(amrescan);

  Assert(nkeys == scan->numberOfKeys);

  Assert(norderbys == scan->numberOfOrderBys);

  /* reset table AM state for rescan */

  if (scan->xs_table_opaque)

    table_index_scan_reset(scan);

  scan->kill_prior_tuple = false; /* for safety */

  scan->xs_heap_continue = false;

  scan->indexRelation->rd_indam->amrescan(scan, keys, nkeys,

                      orderbys, norderbys);

}

/* ----------------

 *    index_endscan - end a scan

 * ----------------

 */

void

index_endscan(IndexScanDesc scan)

{

  SCAN_CHECKS;

  CHECK_SCAN_PROCEDURE(amendscan);

  /* Release resources (like buffer pins) from table accesses */

  if (scan->xs_table_opaque)

    table_index_scan_end(scan);

  /* End the AM's scan */

  scan->indexRelation->rd_indam->amendscan(scan);

  /* Release index refcount acquired by index_beginscan */

  RelationDecrementReferenceCount(scan->indexRelation);

  if (scan->xs_temp_snap)

    UnregisterSnapshot(scan->xs_snapshot);

  /* Release the scan data structure itself */

  IndexScanEnd(scan);

}

/* ----------------

 *    index_markpos  - mark a scan position

 * ----------------

 */

void

index_markpos(IndexScanDesc scan)

{

  SCAN_CHECKS;

  CHECK_SCAN_PROCEDURE(ammarkpos);

  scan->indexRelation->rd_indam->ammarkpos(scan);

}

/* ----------------

 *    index_restrpos  - restore a scan position

 *

 * NOTE: this only restores the internal scan state of the index AM.  See

 * comments for ExecRestrPos().

 *

 * NOTE: For heap, in the presence of HOT chains, mark/restore only works

 * correctly if the scan's snapshot is MVCC-safe; that ensures that there's at

 * most one returnable tuple in each HOT chain, and so restoring the prior

 * state at the granularity of the index AM is sufficient.  Since the only

 * current user of mark/restore functionality is nodeMergejoin.c, this

 * effectively means that merge-join plans only work for MVCC snapshots.  This

 * could be fixed if necessary, but for now it seems unimportant.

 * ----------------

 */

void

index_restrpos(IndexScanDesc scan)

{

  Assert(IsMVCCLikeSnapshot(scan->xs_snapshot));

  SCAN_CHECKS;

  CHECK_SCAN_PROCEDURE(amrestrpos);

  /* reset table AM state for restoring the marked position */

  if (scan->xs_table_opaque)

    table_index_scan_reset(scan);

  scan->kill_prior_tuple = false; /* for safety */

  scan->xs_heap_continue = false;

  scan->indexRelation->rd_indam->amrestrpos(scan);

}

/*

 * Estimates the shared memory needed for parallel scan, including any

 * AM-specific parallel scan state.

 */

Size

index_parallelscan_estimate(Relation indexRelation, int nkeys, int norderbys,

              Snapshot snapshot)

{

  Size    nbytes;

  RELATION_CHECKS;

  nbytes = offsetof(ParallelIndexScanDescData, ps_snapshot_data);

  nbytes = add_size(nbytes, EstimateSnapshotSpace(snapshot));

  nbytes = MAXALIGN(nbytes);

  /*

   * If parallel scan index AM interface can't be used (or index AM provides

   * no such interface), assume there is no AM-specific data needed

   */

  if (indexRelation->rd_indam->amestimateparallelscan != NULL)

    nbytes = add_size(nbytes,

              indexRelation->rd_indam->amestimateparallelscan(indexRelation,

                                      nkeys,

                                      norderbys));

  return nbytes;

}

/*

 * index_parallelscan_initialize - initialize parallel scan

 *

 * We initialize both the ParallelIndexScanDesc proper and the AM-specific

 * information which follows it.

 *

 * This function calls access method specific initialization routine to

 * initialize am specific information.  Call this just once in the leader

 * process; then, individual workers attach via index_beginscan_parallel.

 */

void

index_parallelscan_initialize(Relation heapRelation, Relation indexRelation,

                Snapshot snapshot,

                ParallelIndexScanDesc target)

{

  Size    offset;

  RELATION_CHECKS;

  offset = add_size(offsetof(ParallelIndexScanDescData, ps_snapshot_data),

            EstimateSnapshotSpace(snapshot));

  offset = MAXALIGN(offset);

  target->ps_locator = heapRelation->rd_locator;

  target->ps_indexlocator = indexRelation->rd_locator;

  target->ps_offset_am = 0;

  SerializeSnapshot(snapshot, target->ps_snapshot_data);

  /* aminitparallelscan is optional; assume no-op if not provided by AM */

  if (indexRelation->rd_indam->aminitparallelscan != NULL)

  {

    void     *amtarget;

    target->ps_offset_am = offset;

    amtarget = OffsetToPointer(target, target->ps_offset_am);

    indexRelation->rd_indam->aminitparallelscan(amtarget);

  }

}

/* ----------------

 *    index_parallelrescan  - (re)start a parallel scan of an index

 * ----------------

 */

void

index_parallelrescan(IndexScanDesc scan)

{

  SCAN_CHECKS;

  /* reset table AM state for rescan */

  if (scan->xs_table_opaque)

    table_index_scan_reset(scan);

  /* amparallelrescan is optional; assume no-op if not provided by AM */

  if (scan->indexRelation->rd_indam->amparallelrescan != NULL)

    scan->indexRelation->rd_indam->amparallelrescan(scan);

}

/*

 * index_beginscan_parallel - join parallel index scan

 *

 * flags is a bitmask of ScanOptions affecting the underlying table scan. No

 * SO_INTERNAL_FLAGS are permitted.

 *

 * Caller must be holding suitable locks on the heap and the index.

 */

IndexScanDesc

index_beginscan_parallel(Relation heaprel, Relation indexrel,

             bool index_only_scan,

             IndexScanInstrumentation *instrument,

             int nkeys, int norderbys,

             ParallelIndexScanDesc pscan,

             uint32 flags)

{

  Snapshot  snapshot;

  Assert(RelFileLocatorEquals(heaprel->rd_locator, pscan->ps_locator));

  Assert(RelFileLocatorEquals(indexrel->rd_locator, pscan->ps_indexlocator));

  pg_assume(heaprel != NULL);

  snapshot = RestoreSnapshot(pscan->ps_snapshot_data);

  RegisterSnapshot(snapshot);

  return index_beginscan_internal(indexrel, heaprel, nkeys, norderbys,

                  snapshot, pscan, instrument,

                  index_only_scan, true, flags);

}

/* ----------------

 *    index_getbitmap - get all tuples at once from an index scan

 *

 * Adds the TIDs of all heap tuples satisfying the scan keys to a bitmap.

 * Since there's no interlock between the index scan and the eventual heap

 * access, this is only safe to use with MVCC-based snapshots: the heap

 * item slot could have been replaced by a newer tuple by the time we get

 * to it.

 *

 * Returns the number of matching tuples found.  (Note: this might be only

 * approximate, so it should only be used for statistical purposes.)

 * ----------------

 */

int64

index_getbitmap(IndexScanDesc scan, TIDBitmap *bitmap)

{

  int64   ntids;

  SCAN_CHECKS;

  CHECK_SCAN_PROCEDURE(amgetbitmap);

  /* just make sure this is false... */

  scan->kill_prior_tuple = false;

  /*

   * have the am's getbitmap proc do all the work.

   */

  ntids = scan->indexRelation->rd_indam->amgetbitmap(scan, bitmap);

  pgstat_count_index_tuples(scan->indexRelation, ntids);

  return ntids;

}

/* ----------------

 *    index_bulk_delete - do mass deletion of index entries

 *

 *    callback routine tells whether a given main-heap tuple is

 *    to be deleted

 *

 *    return value is an optional palloc'd struct of statistics

 * ----------------

 */

IndexBulkDeleteResult *

index_bulk_delete(IndexVacuumInfo *info,

          IndexBulkDeleteResult *istat,

          IndexBulkDeleteCallback callback,

          void *callback_state)

{

  Relation  indexRelation = info->index;

  RELATION_CHECKS;

  CHECK_REL_PROCEDURE(ambulkdelete);

  return indexRelation->rd_indam->ambulkdelete(info, istat,

                         callback, callback_state);

}

/* ----------------

 *    index_vacuum_cleanup - do post-deletion cleanup of an index

 *

 *    return value is an optional palloc'd struct of statistics

 * ----------------

 */

IndexBulkDeleteResult *

index_vacuum_cleanup(IndexVacuumInfo *info,

           IndexBulkDeleteResult *istat)

{

  Relation  indexRelation = info->index;

  RELATION_CHECKS;

  CHECK_REL_PROCEDURE(amvacuumcleanup);

  return indexRelation->rd_indam->amvacuumcleanup(info, istat);

}

/* ----------------

 *    index_can_return

 *

 *    Does the index access method support index-only scans for the given

 *    column?

 * ----------------

 */

bool

index_can_return(Relation indexRelation, int attno)

{

  RELATION_CHECKS;

  /* amcanreturn is optional; assume false if not provided by AM */

  if (indexRelation->rd_indam->amcanreturn == NULL)

    return false;

  return indexRelation->rd_indam->amcanreturn(indexRelation, attno);

}

/* ----------------

 *    index_getprocid

 *

 *    Index access methods typically require support routines that are

 *    not directly the implementation of any WHERE-clause query operator

 *    and so cannot be kept in pg_amop.  Instead, such routines are kept

 *    in pg_amproc.  These registered procedure OIDs are assigned numbers

 *    according to a convention established by the access method.

 *    The general index code doesn't know anything about the routines

 *    involved; it just builds an ordered list of them for

 *    each attribute on which an index is defined.

 *

 *    As of Postgres 8.3, support routines within an operator family

 *    are further subdivided by the "left type" and "right type" of the

 *    query operator(s) that they support.  The "default" functions for a

 *    particular indexed attribute are those with both types equal to

 *    the index opclass' opcintype (note that this is subtly different

 *    from the indexed attribute's own type: it may be a binary-compatible

 *    type instead).  Only the default functions are stored in relcache

 *    entries --- access methods can use the syscache to look up non-default

 *    functions.

 *

 *    This routine returns the requested default procedure OID for a

 *    particular indexed attribute.

 * ----------------

 */

RegProcedure

index_getprocid(Relation irel,

        AttrNumber attnum,

        uint16 procnum)

{

  RegProcedure *loc;

  int     nproc;

  int     procindex;

  nproc = irel->rd_indam->amsupport;

  Assert(procnum > 0 && procnum <= (uint16) nproc);

  procindex = (nproc * (attnum - 1)) + (procnum - 1);

  loc = irel->rd_support;

  Assert(loc != NULL);

  return loc[procindex];

}

/* ----------------

 *    index_getprocinfo

 *

 *    This routine allows index AMs to keep fmgr lookup info for

 *    support procs in the relcache.  As above, only the "default"

 *    functions for any particular indexed attribute are cached.

 *

 * Note: the return value points into cached data that will be lost during

 * any relcache rebuild!  Therefore, either use the callinfo right away,

 * or save it only after having acquired some type of lock on the index rel.

 * ----------------

 */

FmgrInfo *

index_getprocinfo(Relation irel,

          AttrNumber attnum,

          uint16 procnum)

{

  FmgrInfo   *locinfo;

  int     nproc;

  int     optsproc;

  int     procindex;

  nproc = irel->rd_indam->amsupport;

  optsproc = irel->rd_indam->amoptsprocnum;

  Assert(procnum > 0 && procnum <= (uint16) nproc);

  procindex = (nproc * (attnum - 1)) + (procnum - 1);

  locinfo = irel->rd_supportinfo;

  Assert(locinfo != NULL);

  locinfo += procindex;

  /* Initialize the lookup info if first time through */

  if (locinfo->fn_oid == InvalidOid)

  {

    RegProcedure *loc = irel->rd_support;

    RegProcedure procId;

    Assert(loc != NULL);

    procId = loc[procindex];

    /*

     * Complain if function was not found during IndexSupportInitialize.

     * This should not happen unless the system tables contain bogus

     * entries for the index opclass.  (If an AM wants to allow a support

     * function to be optional, it can use index_getprocid.)

     */

    if (!RegProcedureIsValid(procId))

      elog(ERROR, "missing support function %d for attribute %d of index \"%s\"",

         procnum, attnum, RelationGetRelationName(irel));

    fmgr_info_cxt(procId, locinfo, irel->rd_indexcxt);

    if (procnum != optsproc)

    {

      /* Initialize locinfo->fn_expr with opclass options Const */

      bytea   **attoptions = RelationGetIndexAttOptions(irel, false);

      MemoryContext oldcxt = MemoryContextSwitchTo(irel->rd_indexcxt);

      set_fn_opclass_options(locinfo, attoptions[attnum - 1]);

      MemoryContextSwitchTo(oldcxt);

    }

  }

  return locinfo;

}

/* ----------------

 *    index_store_float8_orderby_distances

 *

 *    Convert AM distance function's results (that can be inexact)

 *    to ORDER BY types and save them into xs_orderbyvals/xs_orderbynulls

 *    for a possible recheck.

 * ----------------

 */

void

index_store_float8_orderby_distances(IndexScanDesc scan, Oid *orderByTypes,

                   IndexOrderByDistance *distances,

                   bool recheckOrderBy)

{

  int     i;

  Assert(distances || !recheckOrderBy);

  scan->xs_recheckorderby = recheckOrderBy;

  for (i = 0; i < scan->numberOfOrderBys; i++)

  {

    if (orderByTypes[i] == FLOAT8OID)

    {

      if (distances && !distances[i].isnull)

      {

        scan->xs_orderbyvals[i] = Float8GetDatum(distances[i].value);

        scan->xs_orderbynulls[i] = false;

      }

      else

      {

        scan->xs_orderbyvals[i] = (Datum) 0;

        scan->xs_orderbynulls[i] = true;

      }

    }

    else if (orderByTypes[i] == FLOAT4OID)

    {

      /* convert distance function's result to ORDER BY type */

      if (distances && !distances[i].isnull)

      {

        scan->xs_orderbyvals[i] = Float4GetDatum((float4) distances[i].value);

        scan->xs_orderbynulls[i] = false;

      }

      else

      {

        scan->xs_orderbyvals[i] = (Datum) 0;

        scan->xs_orderbynulls[i] = true;

      }

    }

    else

    {

      /*

       * If the ordering operator's return value is anything else, we

       * don't know how to convert the float8 bound calculated by the

       * distance function to that.  The executor won't actually need

       * the order by values we return here, if there are no lossy

       * results, so only insist on converting if the *recheck flag is

       * set.

       */

      if (scan->xs_recheckorderby)

        elog(ERROR, "ORDER BY operator must return float8 or float4 if the distance function is lossy");

      scan->xs_orderbynulls[i] = true;

    }

  }

}

/* ----------------

 *      index_opclass_options

 *

 *      Parse opclass-specific options for index column.

 * ----------------

 */

bytea *

index_opclass_options(Relation indrel, AttrNumber attnum, Datum attoptions,

            bool validate)

{

  int     amoptsprocnum = indrel->rd_indam->amoptsprocnum;

  Oid     procid = InvalidOid;

  FmgrInfo   *procinfo;

  local_relopts relopts;

  /* fetch options support procedure if specified */

  if (amoptsprocnum != 0)

    procid = index_getprocid(indrel, attnum, amoptsprocnum);

  if (!OidIsValid(procid))

  {

    Oid     opclass;

    Datum   indclassDatum;

    oidvector  *indclass;

    if (!DatumGetPointer(attoptions))

      return NULL;   /* ok, no options, no procedure */

    /*

     * Report an error if the opclass's options-parsing procedure does not

     * exist but the opclass options are specified.

     */

    indclassDatum = SysCacheGetAttrNotNull(INDEXRELID, indrel->rd_indextuple,

                         Anum_pg_index_indclass);

    indclass = (oidvector *) DatumGetPointer(indclassDatum);

    opclass = indclass->values[attnum - 1];

    ereport(ERROR,

        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),

         errmsg("operator class %s has no options",

            generate_opclass_name(opclass))));

  }

  init_local_reloptions(&relopts, 0);

  procinfo = index_getprocinfo(indrel, attnum, amoptsprocnum);

  (void) FunctionCall1(procinfo, PointerGetDatum(&relopts));

  return build_local_reloptions(&relopts, attoptions, validate);

}