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

 * relation.c

 *     PostgreSQL logical replication relation mapping cache

 *

 * Copyright (c) 2016-2026, PostgreSQL Global Development Group

 *

 * IDENTIFICATION

 *    src/backend/replication/logical/relation.c

 *

 * NOTES

 *    Routines in this file mainly have to do with mapping the properties

 *    of local replication target relations to the properties of their

 *    remote counterpart.

 *

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

 */

#include "postgres.h"

#include "access/amapi.h"

#include "access/genam.h"

#include "access/table.h"

#include "catalog/namespace.h"

#include "catalog/pg_subscription_rel.h"

#include "executor/executor.h"

#include "nodes/makefuncs.h"

#include "replication/logicalrelation.h"

#include "replication/worker_internal.h"

#include "utils/inval.h"

#include "utils/lsyscache.h"

#include "utils/syscache.h"

#include "utils/typcache.h"

static MemoryContext LogicalRepRelMapContext = NULL;

static HTAB *LogicalRepRelMap = NULL;

/*

 * Partition map (LogicalRepPartMap)

 *

 * When a partitioned table is used as replication target, replicated

 * operations are actually performed on its leaf partitions, which requires

 * the partitions to also be mapped to the remote relation.  Parent's entry

 * (LogicalRepRelMapEntry) cannot be used as-is for all partitions, because

 * individual partitions may have different attribute numbers, which means

 * attribute mappings to remote relation's attributes must be maintained

 * separately for each partition.

 */

static MemoryContext LogicalRepPartMapContext = NULL;

static HTAB *LogicalRepPartMap = NULL;

typedef struct LogicalRepPartMapEntry

{

  Oid     partoid;    /* LogicalRepPartMap's key */

  LogicalRepRelMapEntry relmapentry;

} LogicalRepPartMapEntry;

static Oid  FindLogicalRepLocalIndex(Relation localrel, LogicalRepRelation *remoterel,

                   AttrMap *attrMap, bool *idxisreplident);

/*

 * Relcache invalidation callback for our relation map cache.

 */

static void

logicalrep_relmap_invalidate_cb(Datum arg, Oid reloid)

{

  LogicalRepRelMapEntry *entry;

  /* Just to be sure. */

  if (LogicalRepRelMap == NULL)

    return;

  if (reloid != InvalidOid)

  {

    HASH_SEQ_STATUS status;

    hash_seq_init(&status, LogicalRepRelMap);

    /* TODO, use inverse lookup hashtable? */

    while ((entry = (LogicalRepRelMapEntry *) hash_seq_search(&status)) != NULL)

    {

      if (entry->localreloid == reloid)

      {

        entry->localrelvalid = false;

        hash_seq_term(&status);

        break;

      }

    }

  }

  else

  {

    /* invalidate all cache entries */

    HASH_SEQ_STATUS status;

    hash_seq_init(&status, LogicalRepRelMap);

    while ((entry = (LogicalRepRelMapEntry *) hash_seq_search(&status)) != NULL)

      entry->localrelvalid = false;

  }

}

/*

 * Initialize the relation map cache.

 */

static void

logicalrep_relmap_init(void)

{

  HASHCTL   ctl;

  if (!LogicalRepRelMapContext)

    LogicalRepRelMapContext =

      AllocSetContextCreate(CacheMemoryContext,

                  "LogicalRepRelMapContext",

                  ALLOCSET_DEFAULT_SIZES);

  /* Initialize the relation hash table. */

  ctl.keysize = sizeof(LogicalRepRelId);

  ctl.entrysize = sizeof(LogicalRepRelMapEntry);

  ctl.hcxt = LogicalRepRelMapContext;

  LogicalRepRelMap = hash_create("logicalrep relation map cache", 128, &ctl,

                   HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);

  /* Watch for invalidation events. */

  CacheRegisterRelcacheCallback(logicalrep_relmap_invalidate_cb,

                  (Datum) 0);

}

/*

 * Free the entry of a relation map cache.

 */

static void

logicalrep_relmap_free_entry(LogicalRepRelMapEntry *entry)

{

  LogicalRepRelation *remoterel;

  remoterel = &entry->remoterel;

  pfree(remoterel->nspname);

  pfree(remoterel->relname);

  if (remoterel->natts > 0)

  {

    int     i;

    for (i = 0; i < remoterel->natts; i++)

      pfree(remoterel->attnames[i]);

    pfree(remoterel->attnames);

    pfree(remoterel->atttyps);

  }

  bms_free(remoterel->attkeys);

  if (entry->attrmap)

    free_attrmap(entry->attrmap);

}

/*

 * Add new entry or update existing entry in the relation map cache.

 *

 * Called when new relation mapping is sent by the publisher to update

 * our expected view of incoming data from said publisher.

 */

void

logicalrep_relmap_update(LogicalRepRelation *remoterel)

{

  MemoryContext oldctx;

  LogicalRepRelMapEntry *entry;

  bool    found;

  int     i;

  if (LogicalRepRelMap == NULL)

    logicalrep_relmap_init();

  /*

   * HASH_ENTER returns the existing entry if present or creates a new one.

   */

  entry = hash_search(LogicalRepRelMap, &remoterel->remoteid,

            HASH_ENTER, &found);

  if (found)

    logicalrep_relmap_free_entry(entry);

  memset(entry, 0, sizeof(LogicalRepRelMapEntry));

  /* Make cached copy of the data */

  oldctx = MemoryContextSwitchTo(LogicalRepRelMapContext);

  entry->remoterel.remoteid = remoterel->remoteid;

  entry->remoterel.nspname = pstrdup(remoterel->nspname);

  entry->remoterel.relname = pstrdup(remoterel->relname);

  entry->remoterel.natts = remoterel->natts;

  entry->remoterel.attnames = palloc_array(char *, remoterel->natts);

  entry->remoterel.atttyps = palloc_array(Oid, remoterel->natts);

  for (i = 0; i < remoterel->natts; i++)

  {

    entry->remoterel.attnames[i] = pstrdup(remoterel->attnames[i]);

    entry->remoterel.atttyps[i] = remoterel->atttyps[i];

  }

  entry->remoterel.replident = remoterel->replident;

  /*

   * XXX The walsender currently does not transmit the relkind of the remote

   * relation when replicating changes. Since we support replicating only

   * table changes at present, we default to initializing relkind as

   * RELKIND_RELATION. This is needed in CheckSubscriptionRelkind() to check

   * if the publisher and subscriber relation kinds are compatible.

   */

  entry->remoterel.relkind =

    (remoterel->relkind == 0) ? RELKIND_RELATION : remoterel->relkind;

  entry->remoterel.attkeys = bms_copy(remoterel->attkeys);

  MemoryContextSwitchTo(oldctx);

}

/*

 * Find attribute index in TupleDesc struct by attribute name.

 *

 * Returns -1 if not found.

 */

static int

logicalrep_rel_att_by_name(LogicalRepRelation *remoterel, const char *attname)

{

  int     i;

  for (i = 0; i < remoterel->natts; i++)

  {

    if (strcmp(remoterel->attnames[i], attname) == 0)

      return i;

  }

  return -1;

}

/*

 * Returns a comma-separated string of attribute names based on the provided

 * relation and bitmap indicating which attributes to include.

 */

static char *

logicalrep_get_attrs_str(LogicalRepRelation *remoterel, Bitmapset *atts)

{

  StringInfoData attsbuf;

  bool    first = true;

  int     i = -1;

  Assert(!bms_is_empty(atts));

  initStringInfo(&attsbuf);

  while ((i = bms_next_member(atts, i)) >= 0)

  {

    if (first)

      appendStringInfo(&attsbuf, _("\"%s\""), remoterel->attnames[i]);

    else

      appendStringInfo(&attsbuf, _(", \"%s\""), remoterel->attnames[i]);

    first = false;

  }

  return attsbuf.data;

}

/*

 * If attempting to replicate missing or generated columns, report an error.

 * Prioritize 'missing' errors if both occur though the prioritization is

 * arbitrary.

 */

static void

logicalrep_report_missing_or_gen_attrs(LogicalRepRelation *remoterel,

                     Bitmapset *missingatts,

                     Bitmapset *generatedatts)

{

  if (!bms_is_empty(missingatts))

    ereport(ERROR,

        errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),

        errmsg_plural("logical replication target relation \"%s.%s\" is missing replicated column: %s",

                "logical replication target relation \"%s.%s\" is missing replicated columns: %s",

                bms_num_members(missingatts),

                remoterel->nspname,

                remoterel->relname,

                logicalrep_get_attrs_str(remoterel,

                             missingatts)));

  if (!bms_is_empty(generatedatts))

    ereport(ERROR,

        errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),

        errmsg_plural("logical replication target relation \"%s.%s\" has incompatible generated column: %s",

                "logical replication target relation \"%s.%s\" has incompatible generated columns: %s",

                bms_num_members(generatedatts),

                remoterel->nspname,

                remoterel->relname,

                logicalrep_get_attrs_str(remoterel,

                             generatedatts)));

}

/*

 * Check if replica identity matches and mark the updatable flag.

 *

 * We allow for stricter replica identity (fewer columns) on subscriber as

 * that will not stop us from finding unique tuple. IE, if publisher has

 * identity (id,timestamp) and subscriber just (id) this will not be a

 * problem, but in the opposite scenario it will.

 *

 * We just mark the relation entry as not updatable here if the local

 * replica identity is found to be insufficient for applying

 * updates/deletes (inserts don't care!) and leave it to

 * check_relation_updatable() to throw the actual error if needed.

 */

static void

logicalrep_rel_mark_updatable(LogicalRepRelMapEntry *entry)

{

  Bitmapset  *idkey;

  LogicalRepRelation *remoterel = &entry->remoterel;

  int     i;

  entry->updatable = true;

  idkey = RelationGetIndexAttrBitmap(entry->localrel,

                     INDEX_ATTR_BITMAP_IDENTITY_KEY);

  /* fallback to PK if no replica identity */

  if (idkey == NULL)

  {

    idkey = RelationGetIndexAttrBitmap(entry->localrel,

                       INDEX_ATTR_BITMAP_PRIMARY_KEY);

    /*

     * If no replica identity index and no PK, the published table must

     * have replica identity FULL.

     */

    if (idkey == NULL && remoterel->replident != REPLICA_IDENTITY_FULL)

      entry->updatable = false;

  }

  i = -1;

  while ((i = bms_next_member(idkey, i)) >= 0)

  {

    int     attnum = i + FirstLowInvalidHeapAttributeNumber;

    if (!AttrNumberIsForUserDefinedAttr(attnum))

      ereport(ERROR,

          (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),

           errmsg("logical replication target relation \"%s.%s\" uses "

              "system columns in REPLICA IDENTITY index",

              remoterel->nspname, remoterel->relname)));

    attnum = AttrNumberGetAttrOffset(attnum);

    if (entry->attrmap->attnums[attnum] < 0 ||

      !bms_is_member(entry->attrmap->attnums[attnum], remoterel->attkeys))

    {

      entry->updatable = false;

      break;

    }

  }

}

/*

 * Open the local relation associated with the remote one.

 *

 * Rebuilds the Relcache mapping if it was invalidated by local DDL.

 */

LogicalRepRelMapEntry *

logicalrep_rel_open(LogicalRepRelId remoteid, LOCKMODE lockmode)

{

  LogicalRepRelMapEntry *entry;

  bool    found;

  LogicalRepRelation *remoterel;

  if (LogicalRepRelMap == NULL)

    logicalrep_relmap_init();

  /* Search for existing entry. */

  entry = hash_search(LogicalRepRelMap, &remoteid,

            HASH_FIND, &found);

  if (!found)

    elog(ERROR, "no relation map entry for remote relation ID %u",

       remoteid);

  remoterel = &entry->remoterel;

  /* Ensure we don't leak a relcache refcount. */

  if (entry->localrel)

    elog(ERROR, "remote relation ID %u is already open", remoteid);

  /*

   * When opening and locking a relation, pending invalidation messages are

   * processed which can invalidate the relation.  Hence, if the entry is

   * currently considered valid, try to open the local relation by OID and

   * see if invalidation ensues.

   */

  if (entry->localrelvalid)

  {

    entry->localrel = try_table_open(entry->localreloid, lockmode);

    if (!entry->localrel)

    {

      /* Table was renamed or dropped. */

      entry->localrelvalid = false;

    }

    else if (!entry->localrelvalid)

    {

      /* Note we release the no-longer-useful lock here. */

      table_close(entry->localrel, lockmode);

      entry->localrel = NULL;

    }

  }

  /*

   * If the entry has been marked invalid since we last had lock on it,

   * re-open the local relation by name and rebuild all derived data.

   */

  if (!entry->localrelvalid)

  {

    Oid     relid;

    TupleDesc desc;

    MemoryContext oldctx;

    int     i;

    Bitmapset  *missingatts;

    Bitmapset  *generatedattrs = NULL;

    /* Release the no-longer-useful attrmap, if any. */

    if (entry->attrmap)

    {

      free_attrmap(entry->attrmap);

      entry->attrmap = NULL;

    }

    /* Try to find and lock the relation by name. */

    relid = RangeVarGetRelid(makeRangeVar(remoterel->nspname,

                        remoterel->relname, -1),

                 lockmode, true);

    if (!OidIsValid(relid))

      ereport(ERROR,

          (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),

           errmsg("logical replication target relation \"%s.%s\" does not exist",

              remoterel->nspname, remoterel->relname)));

    entry->localrel = table_open(relid, NoLock);

    entry->localreloid = relid;

    /* Check for supported relkind. */

    CheckSubscriptionRelkind(entry->localrel->rd_rel->relkind,

                 remoterel->relkind,

                 remoterel->nspname, remoterel->relname);

    /*

     * Build the mapping of local attribute numbers to remote attribute

     * numbers and validate that we don't miss any replicated columns as

     * that would result in potentially unwanted data loss.

     */

    desc = RelationGetDescr(entry->localrel);

    oldctx = MemoryContextSwitchTo(LogicalRepRelMapContext);

    entry->attrmap = make_attrmap(desc->natts);

    MemoryContextSwitchTo(oldctx);

    /* check and report missing attrs, if any */

    missingatts = bms_add_range(NULL, 0, remoterel->natts - 1);

    for (i = 0; i < desc->natts; i++)

    {

      int     attnum;

      Form_pg_attribute attr = TupleDescAttr(desc, i);

      if (attr->attisdropped)

      {

        entry->attrmap->attnums[i] = -1;

        continue;

      }

      attnum = logicalrep_rel_att_by_name(remoterel,

                        NameStr(attr->attname));

      entry->attrmap->attnums[i] = attnum;

      if (attnum >= 0)

      {

        /* Remember which subscriber columns are generated. */

        if (attr->attgenerated)

          generatedattrs = bms_add_member(generatedattrs, attnum);

        missingatts = bms_del_member(missingatts, attnum);

      }

    }

    logicalrep_report_missing_or_gen_attrs(remoterel, missingatts,

                         generatedattrs);

    /* be tidy */

    bms_free(generatedattrs);

    bms_free(missingatts);

    /*

     * Set if the table's replica identity is enough to apply

     * update/delete.

     */

    logicalrep_rel_mark_updatable(entry);

    /*

     * Finding a usable index is an infrequent task. It occurs when an

     * operation is first performed on the relation, or after invalidation

     * of the relation cache entry (such as ANALYZE or CREATE/DROP index

     * on the relation).

     */

    entry->localindexoid = FindLogicalRepLocalIndex(entry->localrel, remoterel,

                            entry->attrmap,

                            &entry->idxisreplident);

    entry->localrelvalid = true;

  }

  if (entry->state != SUBREL_STATE_READY)

    entry->state = GetSubscriptionRelState(MySubscription->oid,

                         entry->localreloid,

                         &entry->statelsn);

  return entry;

}

/*

 * Close the previously opened logical relation.

 */

void

logicalrep_rel_close(LogicalRepRelMapEntry *rel, LOCKMODE lockmode)

{

  table_close(rel->localrel, lockmode);

  rel->localrel = NULL;

}

/*

 * Partition cache: look up partition LogicalRepRelMapEntry's

 *

 * Unlike relation map cache, this is keyed by partition OID, not remote

 * relation OID, because we only have to use this cache in the case where

 * partitions are not directly mapped to any remote relation, such as when

 * replication is occurring with one of their ancestors as target.

 */

/*

 * Relcache invalidation callback

 */

static void

logicalrep_partmap_invalidate_cb(Datum arg, Oid reloid)

{

  LogicalRepPartMapEntry *entry;

  /* Just to be sure. */

  if (LogicalRepPartMap == NULL)

    return;

  if (reloid != InvalidOid)

  {

    /*

     * LogicalRepPartMap is keyed by partition OID, matching with

     * entry->relmapentry.localreloid (see logicalrep_partition_open), so

     * we can invalidate via a direct hash lookup.

     */

    entry = hash_search(LogicalRepPartMap, &reloid, HASH_FIND, NULL);

    if (entry != NULL)

      entry->relmapentry.localrelvalid = false;

  }

  else

  {

    /* invalidate all cache entries */

    HASH_SEQ_STATUS status;

    hash_seq_init(&status, LogicalRepPartMap);

    while ((entry = (LogicalRepPartMapEntry *) hash_seq_search(&status)) != NULL)

      entry->relmapentry.localrelvalid = false;

  }

}

/*

 * Reset the entries in the partition map that refer to remoterel.

 *

 * Called when new relation mapping is sent by the publisher to update our

 * expected view of incoming data from said publisher.

 *

 * Note that we don't update the remoterel information in the entry here,

 * we will update the information in logicalrep_partition_open to avoid

 * unnecessary work.

 */

void

logicalrep_partmap_reset_relmap(LogicalRepRelation *remoterel)

{

  HASH_SEQ_STATUS status;

  LogicalRepPartMapEntry *part_entry;

  LogicalRepRelMapEntry *entry;

  if (LogicalRepPartMap == NULL)

    return;

  hash_seq_init(&status, LogicalRepPartMap);

  while ((part_entry = (LogicalRepPartMapEntry *) hash_seq_search(&status)) != NULL)

  {

    entry = &part_entry->relmapentry;

    if (entry->remoterel.remoteid != remoterel->remoteid)

      continue;

    logicalrep_relmap_free_entry(entry);

    memset(entry, 0, sizeof(LogicalRepRelMapEntry));

  }

}

/*

 * Initialize the partition map cache.

 */

static void

logicalrep_partmap_init(void)

{

  HASHCTL   ctl;

  if (!LogicalRepPartMapContext)

    LogicalRepPartMapContext =

      AllocSetContextCreate(CacheMemoryContext,

                  "LogicalRepPartMapContext",

                  ALLOCSET_DEFAULT_SIZES);

  /* Initialize the relation hash table. */

  ctl.keysize = sizeof(Oid);  /* partition OID */

  ctl.entrysize = sizeof(LogicalRepPartMapEntry);

  ctl.hcxt = LogicalRepPartMapContext;

  LogicalRepPartMap = hash_create("logicalrep partition map cache", 64, &ctl,

                  HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);

  /* Watch for invalidation events. */

  CacheRegisterRelcacheCallback(logicalrep_partmap_invalidate_cb,

                  (Datum) 0);

}

/*

 * logicalrep_partition_open

 *

 * Returned entry reuses most of the values of the root table's entry, save

 * the attribute map, which can be different for the partition.  However,

 * we must physically copy all the data, in case the root table's entry

 * gets freed/rebuilt.

 *

 * Note there's no logicalrep_partition_close, because the caller closes the

 * component relation.

 */

LogicalRepRelMapEntry *

logicalrep_partition_open(LogicalRepRelMapEntry *root,

              Relation partrel, AttrMap *map)

{

  LogicalRepRelMapEntry *entry;

  LogicalRepPartMapEntry *part_entry;

  LogicalRepRelation *remoterel = &root->remoterel;

  Oid     partOid = RelationGetRelid(partrel);

  AttrMap    *attrmap = root->attrmap;

  bool    found;

  MemoryContext oldctx;

  if (LogicalRepPartMap == NULL)

    logicalrep_partmap_init();

  /* Search for existing entry. */

  part_entry = (LogicalRepPartMapEntry *) hash_search(LogicalRepPartMap,

                            &partOid,

                            HASH_ENTER, &found);

  entry = &part_entry->relmapentry;

  /*

   * We must always overwrite entry->localrel with the latest partition

   * Relation pointer, because the Relation pointed to by the old value may

   * have been cleared after the caller would have closed the partition

   * relation after the last use of this entry.  Note that localrelvalid is

   * only updated by the relcache invalidation callback, so it may still be

   * true irrespective of whether the Relation pointed to by localrel has

   * been cleared or not.

   */

  if (found && entry->localrelvalid)

  {

    Assert(entry->localreloid == partOid);

    entry->localrel = partrel;

    return entry;

  }

  /* Switch to longer-lived context. */

  oldctx = MemoryContextSwitchTo(LogicalRepPartMapContext);

  if (!found)

  {

    memset(part_entry, 0, sizeof(LogicalRepPartMapEntry));

    part_entry->partoid = partOid;

  }

  /* Release the no-longer-useful attrmap, if any. */

  if (entry->attrmap)

  {

    free_attrmap(entry->attrmap);

    entry->attrmap = NULL;

  }

  if (!entry->remoterel.remoteid)

  {

    int     i;

    /* Remote relation is copied as-is from the root entry. */

    entry->remoterel.remoteid = remoterel->remoteid;

    entry->remoterel.nspname = pstrdup(remoterel->nspname);

    entry->remoterel.relname = pstrdup(remoterel->relname);

    entry->remoterel.natts = remoterel->natts;

    entry->remoterel.attnames = palloc_array(char *, remoterel->natts);

    entry->remoterel.atttyps = palloc_array(Oid, remoterel->natts);

    for (i = 0; i < remoterel->natts; i++)

    {

      entry->remoterel.attnames[i] = pstrdup(remoterel->attnames[i]);

      entry->remoterel.atttyps[i] = remoterel->atttyps[i];

    }

    entry->remoterel.replident = remoterel->replident;

    entry->remoterel.attkeys = bms_copy(remoterel->attkeys);

  }

  entry->localrel = partrel;

  entry->localreloid = partOid;

  /*

   * If the partition's attributes don't match the root relation's, we'll

   * need to make a new attrmap which maps partition attribute numbers to

   * remoterel's, instead of the original which maps root relation's

   * attribute numbers to remoterel's.

   *

   * Note that 'map' which comes from the tuple routing data structure

   * contains 1-based attribute numbers (of the parent relation).  However,

   * the map in 'entry', a logical replication data structure, contains

   * 0-based attribute numbers (of the remote relation).

   */

  if (map)

  {

    AttrNumber  attno;

    entry->attrmap = make_attrmap(map->maplen);

    for (attno = 0; attno < entry->attrmap->maplen; attno++)

    {

      AttrNumber  root_attno = map->attnums[attno];

      /* 0 means it's a dropped attribute.  See comments atop AttrMap. */

      if (root_attno == 0)

        entry->attrmap->attnums[attno] = -1;

      else

        entry->attrmap->attnums[attno] = attrmap->attnums[root_attno - 1];

    }

  }

  else

  {

    /* Lacking copy_attmap, do this the hard way. */

    entry->attrmap = make_attrmap(attrmap->maplen);

    memcpy(entry->attrmap->attnums, attrmap->attnums,

         attrmap->maplen * sizeof(AttrNumber));

  }

  /* Set if the table's replica identity is enough to apply update/delete. */

  logicalrep_rel_mark_updatable(entry);

  /* state and statelsn are left set to 0. */

  MemoryContextSwitchTo(oldctx);

  /*

   * Finding a usable index is an infrequent task. It occurs when an

   * operation is first performed on the relation, or after invalidation of

   * the relation cache entry (such as ANALYZE or CREATE/DROP index on the

   * relation).

   *

   * We also prefer to run this code on the oldctx so that we do not leak

   * anything in the LogicalRepPartMapContext (hence CacheMemoryContext).

   */

  entry->localindexoid = FindLogicalRepLocalIndex(partrel, remoterel,

                          entry->attrmap,

                          &entry->idxisreplident);

  entry->localrelvalid = true;

  return entry;

}

/*

 * Returns the oid of an index that can be used by the apply worker to scan

 * the relation.

 *

 * We expect to call this function when REPLICA IDENTITY FULL is defined for

 * the remote relation.

 *

 * If no suitable index is found, returns InvalidOid.

 */

static Oid

FindUsableIndexForReplicaIdentityFull(Relation localrel, AttrMap *attrmap)

{

  List     *idxlist = RelationGetIndexList(localrel);

  foreach_oid(idxoid, idxlist)

  {

    bool    isUsableIdx;

    Relation  idxRel;

    idxRel = index_open(idxoid, AccessShareLock);

    /*

     * indisvalid is checked here, not in

     * IsIndexUsableForReplicaIdentityFull(), since that function's other

     * caller (an assertion) must tolerate an index made transiently

     * invalid by a concurrent DROP INDEX CONCURRENTLY, whereas a

     * permanently invalid leftover of a failed CREATE INDEX CONCURRENTLY

     * must never be chosen here.

     */

    isUsableIdx = idxRel->rd_index->indisvalid &&

      IsIndexUsableForReplicaIdentityFull(idxRel, attrmap);

    index_close(idxRel, AccessShareLock);

    /* Return the first eligible index found */

    if (isUsableIdx)

      return idxoid;

  }

  return InvalidOid;

}

/*

 * Returns true if the index is usable for replica identity full.

 *

 * The index must have an equal strategy for each key column, be non-partial,

 * and the leftmost field must be a column (not an expression) that references

 * the remote relation column. These limitations help to keep the index scan

 * similar to PK/RI index scans.

 *

 * attrmap is a map of local attributes to remote ones. We can consult this

 * map to check whether the local index attribute has a corresponding remote

 * attribute.

 *

 * Note that this function does not check indisvalid. Callers that are

 * selecting an index to use for future lookups must check indisvalid

 * themselves and reject invalid indexes.

 *

 * Note that the limitations of index scans for replica identity full only

 * adheres to a subset of the limitations of PK/RI. For example, we support

 * columns that are marked as [NULL] or we are not interested in the [NOT

 * DEFERRABLE] aspect of constraints here. It works for us because we always

 * compare the tuples for non-PK/RI index scans. See

 * RelationFindReplTupleByIndex().

 *

 * XXX: To support partial indexes, the required changes are likely to be larger.

 * If none of the tuples satisfy the expression for the index scan, we fall-back

 * to sequential execution, which might not be a good idea in some cases.

 */

bool

IsIndexUsableForReplicaIdentityFull(Relation idxrel, AttrMap *attrmap)

{

  AttrNumber  keycol;

  oidvector  *indclass;

  /* The index must not be a partial index */

  if (!heap_attisnull(idxrel->rd_indextuple, Anum_pg_index_indpred, NULL))

    return false;

  Assert(idxrel->rd_index->indnatts >= 1);

  indclass = (oidvector *) DatumGetPointer(SysCacheGetAttrNotNull(INDEXRELID,

                                  idxrel->rd_indextuple,

                                  Anum_pg_index_indclass));

  /* Ensure that the index has a valid equal strategy for each key column */

  for (int i = 0; i < idxrel->rd_index->indnkeyatts; i++)

  {

    Oid     opfamily;

    opfamily = get_opclass_family(indclass->values[i]);

    if (IndexAmTranslateCompareType(COMPARE_EQ, idxrel->rd_rel->relam, opfamily, true) == InvalidStrategy)

      return false;

  }

  /*

   * For indexes other than PK and REPLICA IDENTITY, we need to match the

   * local and remote tuples.  The equality routine tuples_equal() cannot

   * accept a data type where the type cache cannot provide an equality

   * operator.

   */

  for (int i = 0; i < idxrel->rd_att->natts; i++)

  {

    TypeCacheEntry *typentry;

    typentry = lookup_type_cache(TupleDescAttr(idxrel->rd_att, i)->atttypid, TYPECACHE_EQ_OPR_FINFO);

    if (!OidIsValid(typentry->eq_opr_finfo.fn_oid))

      return false;

  }

  /* The leftmost index field must not be an expression */

  keycol = idxrel->rd_index->indkey.values[0];

  if (!AttributeNumberIsValid(keycol))

    return false;

  /*

   * And the leftmost index field must reference the remote relation column.

   * This is because if it doesn't, the sequential scan is favorable over

   * index scan in most cases.

   */

  if (attrmap->maplen <= AttrNumberGetAttrOffset(keycol) ||

    attrmap->attnums[AttrNumberGetAttrOffset(keycol)] < 0)

    return false;

  /*

   * The given index access method must implement "amgettuple", which will

   * be used later to fetch the tuples.  See RelationFindReplTupleByIndex().

   */

  if (GetIndexAmRoutineByAmId(idxrel->rd_rel->relam, false)->amgettuple == NULL)

    return false;

  return true;

}

/*

 * Return the OID of the replica identity index if one is defined;

 * the OID of the PK if one exists and is not deferrable;

 * otherwise, InvalidOid.

 */

Oid

GetRelationIdentityOrPK(Relation rel)

{

  Oid     idxoid;

  idxoid = RelationGetReplicaIndex(rel);

  if (!OidIsValid(idxoid))

    idxoid = RelationGetPrimaryKeyIndex(rel, false);

  return idxoid;

}

/*

 * Returns the index oid if we can use an index for subscriber. Otherwise,

 * returns InvalidOid.

 *

 * '*idxisreplident' is true if the returned index is the relation's replica

 * identity or primary key, and false otherwise.

 */

static Oid

FindLogicalRepLocalIndex(Relation localrel, LogicalRepRelation *remoterel,

             AttrMap *attrMap, bool *idxisreplident)

{

  Oid     idxoid;

  *idxisreplident = false;