Function CreateNodeSetHashTable

src/backend/optimizer/util/predtest_valueset.c:89–104

* returns a hashtable that can be used to map from a node to itself */

 * returns a hashtable that can be used to map from a node to itself
 */
static HTAB*
CreateNodeSetHashTable(MemoryContext memoryContext)
{
	HASHCTL	hash_ctl;

	MemSet(&hash_ctl, 0, sizeof(hash_ctl));

	hash_ctl.keysize = sizeof(Const **);
	hash_ctl.entrysize = sizeof(ConstHashValue);
	hash_ctl.hash = ConstHashTableHash;
	hash_ctl.match = ConstHashTableMatch;
	hash_ctl.hcxt = memoryContext;

	return hash_create("ConstantSet", 16, &hash_ctl,
					   HASH_ELEM | HASH_FUNCTION | HASH_COMPARE | HASH_CONTEXT);
}

/**
 * basic operation on PossibleValueSet:  initialize to "any value possible"