Function FindTupleHashEntry

src/backend/executor/execGrouping.c:403–426

* Search for a hashtable entry matching the given tuple. No entry is * created if there's not a match. This is similar to the non-creating * case of LookupTupleHashEntry, except that it supports cross-type * comparisons, in which the given tuple is not of the same type as the * table entries. The caller must provide the hash functions to use for * the input tuple, as well as the equality f

 * different from the table's internal functions.
 */
TupleHashEntry
FindTupleHashEntry(TupleHashTable hashtable, TupleTableSlot *slot,
				   ExprState *eqcomp,
				   FmgrInfo *hashfunctions)
{
	TupleHashEntry entry;
	MemoryContext oldContext;
	MinimalTuple key;

	/* 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 = hashfunctions;
	hashtable->cur_eq_func = eqcomp;

	/* Search the hash table */
	key = NULL;					/* flag to reference inputslot */
	entry = tuplehash_lookup(hashtable->hashtab, key);
	MemoryContextSwitchTo(oldContext);

	return entry;
}

/*
 * If tuple is NULL, use the input slot instead. This convention avoids the