Function lookup_ts_parser_cache

src/backend/utils/cache/ts_cache.c:110–202

* Fetch parser cache entry */

 * Fetch parser cache entry
 */
TSParserCacheEntry *
lookup_ts_parser_cache(Oid prsId)
{
	TSParserCacheEntry *entry;

	if (TSParserCacheHash == NULL)
	{
		/* First time through: initialize the hash table */
		HASHCTL		ctl;

		ctl.keysize = sizeof(Oid);
		ctl.entrysize = sizeof(TSParserCacheEntry);
		TSParserCacheHash = hash_create("Tsearch parser cache", 4,
										&ctl, HASH_ELEM | HASH_BLOBS);
		/* Flush cache on pg_ts_parser changes */
		CacheRegisterSyscacheCallback(TSPARSEROID, InvalidateTSCacheCallBack,
									  PointerGetDatum(TSParserCacheHash));

		/* Also make sure CacheMemoryContext exists */
		if (!CacheMemoryContext)
			CreateCacheMemoryContext();
	}

	/* Check single-entry cache */
	if (lastUsedParser && lastUsedParser->prsId == prsId &&
		lastUsedParser->isvalid)
		return lastUsedParser;

	/* Try to look up an existing entry */
	entry = (TSParserCacheEntry *) hash_search(TSParserCacheHash,
											   (void *) &prsId,
											   HASH_FIND, NULL);
	if (entry == NULL || !entry->isvalid)
	{
		/*
		 * If we didn't find one, we want to make one. But first look up the
		 * object to be sure the OID is real.
		 */
		HeapTuple	tp;
		Form_pg_ts_parser prs;

		tp = SearchSysCache1(TSPARSEROID, ObjectIdGetDatum(prsId));
		if (!HeapTupleIsValid(tp))
			elog(ERROR, "cache lookup failed for text search parser %u",
				 prsId);
		prs = (Form_pg_ts_parser) GETSTRUCT(tp);

		/*
		 * Sanity checks
		 */
		if (!OidIsValid(prs->prsstart))
			elog(ERROR, "text search parser %u has no prsstart method", prsId);
		if (!OidIsValid(prs->prstoken))
			elog(ERROR, "text search parser %u has no prstoken method", prsId);
		if (!OidIsValid(prs->prsend))
			elog(ERROR, "text search parser %u has no prsend method", prsId);

		if (entry == NULL)