Function RelationGetIndexList

src/backend/utils/cache/relcache.c:4942–5038

* RelationGetIndexList -- get a list of OIDs of indexes on this relation * * The index list is created only if someone requests it. We scan pg_index * to find relevant indexes, and add the list to the relcache entry so that * we won't have to compute it again. Note that shared cache inval of a * relcache entry will delete the old list and set rd_indexvalid to false, * so that we must recom

 * replication identity index, or InvalidOid if there is no such index.
 */
List *
RelationGetIndexList(Relation relation)
{
	Relation	indrel;
	SysScanDesc indscan;
	ScanKeyData skey;
	HeapTuple	htup;
	List	   *result;
	List	   *oldlist;
	char		replident = relation->rd_rel->relreplident;
	Oid			pkeyIndex = InvalidOid;
	Oid			candidateIndex = InvalidOid;
	MemoryContext oldcxt;

	/* Quick exit if we already computed the list. */
	if (relation->rd_indexvalid)
		return list_copy(relation->rd_indexlist);

	/*
	 * We build the list we intend to return (in the caller's context) while
	 * doing the scan.  After successfully completing the scan, we copy that
	 * list into the relcache entry.  This avoids cache-context memory leakage
	 * if we get some sort of error partway through.
	 */
	result = NIL;

	/* Prepare to scan pg_index for entries having indrelid = this rel. */
	ScanKeyInit(&skey,
				Anum_pg_index_indrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(relation)));

	indrel = table_open(IndexRelationId, AccessShareLock);
	indscan = systable_beginscan(indrel, IndexIndrelidIndexId, true,
								 NULL, 1, &skey);

	while (HeapTupleIsValid(htup = systable_getnext(indscan)))
	{
		Form_pg_index index = (Form_pg_index) GETSTRUCT(htup);

		/*
		 * Ignore any indexes that are currently being dropped.  This will
		 * prevent them from being searched, inserted into, or considered in
		 * HOT-safety decisions.  It's unsafe to touch such an index at all
		 * since its catalog entries could disappear at any instant.
		 */
		if (!index->indislive)
			continue;

		/* add index's OID to result list */
		result = lappend_oid(result, index->indexrelid);

		/*
		 * Invalid, non-unique, non-immediate or predicate indexes aren't
		 * interesting for either oid indexes or replication identity indexes,
		 * so don't check them.
		 */
		if (!index->indisvalid || !index->indisunique ||