Function LookupTupleHashEntry_internal

src/backend/executor/execGrouping.c:506–542

* Does the work of LookupTupleHashEntry and LookupTupleHashEntryHash. Useful * so that we can avoid switching the memory context multiple times for * LookupTupleHashEntry. * * NB: This function may or may not change the memory context. Caller is * expected to change it back. */

 * expected to change it back.
 */
static inline TupleHashEntry
LookupTupleHashEntry_internal(TupleHashTable hashtable, TupleTableSlot *slot,
							  bool *isnew, uint32 hash)
{
	TupleHashEntryData *entry;
	bool		found;
	MinimalTuple key;

	key = NULL;					/* flag to reference inputslot */

	if (isnew)
	{
		entry = tuplehash_insert_hash(hashtable->hashtab, key, hash, &found);

		if (found)
		{
			/* found pre-existing entry */
			*isnew = false;
		}
		else
		{
			/* created new entry */
			*isnew = true;
			/* zero caller data */
			entry->additional = NULL;
			MemoryContextSwitchTo(hashtable->tablecxt);
			/* Copy the first tuple into the table context */
			entry->firstTuple = ExecCopySlotMinimalTuple(slot);
		}
	}
	else
	{
		entry = tuplehash_lookup_hash(hashtable->hashtab, key, hash);
	}

	return entry;
}

/*
 * See whether two tuples (presumably of the same hash value) match