Function SearchCatCacheInternal

src/backend/utils/cache/catcache.c:1253–1356

* Work-horse for SearchCatCache/SearchCatCacheN. */

 * Work-horse for SearchCatCache/SearchCatCacheN.
 */
static inline HeapTuple
SearchCatCacheInternal(CatCache *cache,
					   int nkeys,
					   Datum v1,
					   Datum v2,
					   Datum v3,
					   Datum v4)
{
	Datum		arguments[CATCACHE_MAXKEYS];
	uint32		hashValue;
	Index		hashIndex;
	dlist_iter	iter;
	dlist_head *bucket;
	CatCTup    *ct;

	/* Make sure we're in an xact, even if this ends up being a cache hit */
	Assert(IsTransactionState());

	Assert(cache->cc_nkeys == nkeys);

	/*
	 * one-time startup overhead for each cache
	 */
	if (unlikely(cache->cc_tupdesc == NULL))
		CatalogCacheInitializeCache(cache);

#ifdef CATCACHE_STATS
	cache->cc_searches++;
#endif

	/* Initialize local parameter array */
	arguments[0] = v1;
	arguments[1] = v2;
	arguments[2] = v3;
	arguments[3] = v4;

	/*
	 * find the hash bucket in which to look for the tuple
	 */
	hashValue = CatalogCacheComputeHashValue(cache, nkeys, v1, v2, v3, v4);
	hashIndex = HASH_INDEX(hashValue, cache->cc_nbuckets);

	/*
	 * scan the hash bucket until we find a match or exhaust our tuples
	 *
	 * Note: it's okay to use dlist_foreach here, even though we modify the
	 * dlist within the loop, because we don't continue the loop afterwards.
	 */
	bucket = &cache->cc_bucket[hashIndex];
	dlist_foreach(iter, bucket)
	{
		ct = dlist_container(CatCTup, cache_elem, iter.cur);

		if (ct->dead)
			continue;			/* ignore dead entries */

		if (ct->hash_value != hashValue)
			continue;			/* quickly skip entry if wrong hash val */