Function CatalogCacheComputeHashValue

src/backend/utils/cache/catcache.c:270–312

* CatalogCacheComputeHashValue * * Compute the hash value associated with a given set of lookup keys */

 * Compute the hash value associated with a given set of lookup keys
 */
static uint32
CatalogCacheComputeHashValue(CatCache *cache, int nkeys,
							 Datum v1, Datum v2, Datum v3, Datum v4)
{
	uint32		hashValue = 0;
	uint32		oneHash;
	CCHashFN   *cc_hashfunc = cache->cc_hashfunc;

	CACHE_elog(DEBUG2, "CatalogCacheComputeHashValue %s %d %p",
			   cache->cc_relname, nkeys, cache);

	switch (nkeys)
	{
		case 4:
			oneHash = (cc_hashfunc[3]) (v4);

			hashValue ^= oneHash << 24;
			hashValue ^= oneHash >> 8;
			/* FALLTHROUGH */
		case 3:
			oneHash = (cc_hashfunc[2]) (v3);

			hashValue ^= oneHash << 16;
			hashValue ^= oneHash >> 16;
			/* FALLTHROUGH */
		case 2:
			oneHash = (cc_hashfunc[1]) (v2);

			hashValue ^= oneHash << 8;
			hashValue ^= oneHash >> 24;
			/* FALLTHROUGH */
		case 1:
			oneHash = (cc_hashfunc[0]) (v1);

			hashValue ^= oneHash;
			break;
		default:
			elog(FATAL, "wrong number of hash keys: %d", nkeys);
			break;
	}

	return hashValue;
}

/*
 *		CatalogCacheComputeTupleHashValue