Function LookupTupleHashEntry

src/backend/executor/execGrouping.c:316–343

* Find or create a hashtable entry for the tuple group containing the * given tuple. The tuple must be the same type as the hashtable entries. * * If isnew is NULL, we do not create new entries; we return NULL if no * match is found. * * If hash is not NULL, we set it to the calculated hash value. This allows * callers access to the hash value even if no entry is returned. * * If isnew i

 * been zeroed.
 */
TupleHashEntry
LookupTupleHashEntry(TupleHashTable hashtable, TupleTableSlot *slot,
					 bool *isnew, uint32 *hash)
{
	TupleHashEntry entry;
	MemoryContext oldContext;
	uint32		local_hash;

	/* Need to run the hash functions in short-lived context */
	oldContext = MemoryContextSwitchTo(hashtable->tempcxt);

	/* set up data needed by hash and match functions */
	hashtable->inputslot = slot;
	hashtable->in_hash_funcs = hashtable->tab_hash_funcs;
	hashtable->cur_eq_func = hashtable->tab_eq_func;

	local_hash = TupleHashTableHash_internal(hashtable->hashtab, NULL);
	entry = LookupTupleHashEntry_internal(hashtable, slot, isnew, local_hash);

	if (hash != NULL)
		*hash = local_hash;

	Assert(entry == NULL || entry->hash == local_hash);

	MemoryContextSwitchTo(oldContext);

	return entry;
}

/*
 * Compute the hash value for a tuple