syscache.c

来自「PostgreSQL7.4.6 for Linux」· C语言 代码 · 共 731 行 · 第 1/2 页

	{RelationRelationName,		/* RELOID */
		ClassOidIndex,
		ObjectIdAttributeNumber,
		1,
		{
			ObjectIdAttributeNumber,
			0,
			0,
			0
	}},
	{RewriteRelationName,		/* RULERELNAME */
		RewriteRelRulenameIndex,
		Anum_pg_rewrite_ev_class,
		2,
		{
			Anum_pg_rewrite_ev_class,
			Anum_pg_rewrite_rulename,
			0,
			0
	}},
	{ShadowRelationName,		/* SHADOWNAME */
		ShadowNameIndex,
		0,
		1,
		{
			Anum_pg_shadow_usename,
			0,
			0,
			0
	}},
	{ShadowRelationName,		/* SHADOWSYSID */
		ShadowSysidIndex,
		0,
		1,
		{
			Anum_pg_shadow_usesysid,
			0,
			0,
			0
	}},
	{StatisticRelationName,		/* STATRELATT */
		StatisticRelidAttnumIndex,
		Anum_pg_statistic_starelid,
		2,
		{
			Anum_pg_statistic_starelid,
			Anum_pg_statistic_staattnum,
			0,
			0
	}},
	{TypeRelationName,			/* TYPENAMENSP */
		TypeNameNspIndex,
		Anum_pg_type_typrelid,
		2,
		{
			Anum_pg_type_typname,
			Anum_pg_type_typnamespace,
			0,
			0
	}},
	{TypeRelationName,			/* TYPEOID */
		TypeOidIndex,
		Anum_pg_type_typrelid,
		1,
		{
			ObjectIdAttributeNumber,
			0,
			0,
			0
	}}
};

static CatCache *SysCache[lengthof(cacheinfo)];
static int	SysCacheSize = lengthof(cacheinfo);
static bool CacheInitialized = false;


/*
 * InitCatalogCache - initialize the caches
 *
 * Note that no database access is done here; we only allocate memory
 * and initialize the cache structure.	Interrogation of the database
 * to complete initialization of a cache happens upon first use
 * of that cache.
 */
void
InitCatalogCache(void)
{
	int			cacheId;

	Assert(!CacheInitialized);

	MemSet((char *) SysCache, 0, sizeof(SysCache));

	for (cacheId = 0; cacheId < SysCacheSize; cacheId++)
	{
		SysCache[cacheId] = InitCatCache(cacheId,
										 cacheinfo[cacheId].name,
										 cacheinfo[cacheId].indname,
										 cacheinfo[cacheId].reloidattr,
										 cacheinfo[cacheId].nkeys,
										 cacheinfo[cacheId].key);
		if (!PointerIsValid(SysCache[cacheId]))
			elog(ERROR, "could not initialize cache %s (%d)",
				 cacheinfo[cacheId].name, cacheId);
	}
	CacheInitialized = true;
}


/*
 * InitCatalogCachePhase2 - finish initializing the caches
 *
 * Finish initializing all the caches, including necessary database
 * access.
 *
 * This is *not* essential; normally we allow syscaches to be initialized
 * on first use.  However, it is useful as a mechanism to preload the
 * relcache with entries for the most-commonly-used system catalogs.
 * Therefore, we invoke this routine when we need to write a new relcache
 * init file.
 */
void
InitCatalogCachePhase2(void)
{
	int			cacheId;

	Assert(CacheInitialized);

	for (cacheId = 0; cacheId < SysCacheSize; cacheId++)
		InitCatCachePhase2(SysCache[cacheId]);
}


/*
 * SearchSysCache
 *
 *	A layer on top of SearchCatCache that does the initialization and
 *	key-setting for you.
 *
 *	Returns the cache copy of the tuple if one is found, NULL if not.
 *	The tuple is the 'cache' copy and must NOT be modified!
 *
 *	When the caller is done using the tuple, call ReleaseSysCache()
 *	to release the reference count grabbed by SearchSysCache().  If this
 *	is not done, the tuple will remain locked in cache until end of
 *	transaction, which is tolerable but not desirable.
 *
 *	CAUTION: The tuple that is returned must NOT be freed by the caller!
 */
HeapTuple
SearchSysCache(int cacheId,
			   Datum key1,
			   Datum key2,
			   Datum key3,
			   Datum key4)
{
	if (cacheId < 0 || cacheId >= SysCacheSize ||
		!PointerIsValid(SysCache[cacheId]))
		elog(ERROR, "invalid cache id: %d", cacheId);

	return SearchCatCache(SysCache[cacheId], key1, key2, key3, key4);
}

/*
 * ReleaseSysCache
 *		Release previously grabbed reference count on a tuple
 */
void
ReleaseSysCache(HeapTuple tuple)
{
	ReleaseCatCache(tuple);
}

/*
 * SearchSysCacheCopy
 *
 * A convenience routine that does SearchSysCache and (if successful)
 * returns a modifiable copy of the syscache entry.  The original
 * syscache entry is released before returning.  The caller should
 * heap_freetuple() the result when done with it.
 */
HeapTuple
SearchSysCacheCopy(int cacheId,
				   Datum key1,
				   Datum key2,
				   Datum key3,
				   Datum key4)
{
	HeapTuple	tuple,
				newtuple;

	tuple = SearchSysCache(cacheId, key1, key2, key3, key4);
	if (!HeapTupleIsValid(tuple))
		return tuple;
	newtuple = heap_copytuple(tuple);
	ReleaseSysCache(tuple);
	return newtuple;
}

/*
 * SearchSysCacheExists
 *
 * A convenience routine that just probes to see if a tuple can be found.
 * No lock is retained on the syscache entry.
 */
bool
SearchSysCacheExists(int cacheId,
					 Datum key1,
					 Datum key2,
					 Datum key3,
					 Datum key4)
{
	HeapTuple	tuple;

	tuple = SearchSysCache(cacheId, key1, key2, key3, key4);
	if (!HeapTupleIsValid(tuple))
		return false;
	ReleaseSysCache(tuple);
	return true;
}

/*
 * GetSysCacheOid
 *
 * A convenience routine that does SearchSysCache and returns the OID
 * of the found tuple, or InvalidOid if no tuple could be found.
 * No lock is retained on the syscache entry.
 */
Oid
GetSysCacheOid(int cacheId,
			   Datum key1,
			   Datum key2,
			   Datum key3,
			   Datum key4)
{
	HeapTuple	tuple;
	Oid			result;

	tuple = SearchSysCache(cacheId, key1, key2, key3, key4);
	if (!HeapTupleIsValid(tuple))
		return InvalidOid;
	result = HeapTupleGetOid(tuple);
	ReleaseSysCache(tuple);
	return result;
}


/*
 * SearchSysCacheAttName
 *
 * This routine is equivalent to SearchSysCache on the ATTNAME cache,
 * except that it will return NULL if the found attribute is marked
 * attisdropped.  This is convenient for callers that want to act as
 * though dropped attributes don't exist.
 */
HeapTuple
SearchSysCacheAttName(Oid relid, const char *attname)
{
	HeapTuple	tuple;

	tuple = SearchSysCache(ATTNAME,
						   ObjectIdGetDatum(relid),
						   CStringGetDatum(attname),
						   0, 0);
	if (!HeapTupleIsValid(tuple))
		return NULL;
	if (((Form_pg_attribute) GETSTRUCT(tuple))->attisdropped)
	{
		ReleaseSysCache(tuple);
		return NULL;
	}
	return tuple;
}

/*
 * SearchSysCacheCopyAttName
 *
 * As above, an attisdropped-aware version of SearchSysCacheCopy.
 */
HeapTuple
SearchSysCacheCopyAttName(Oid relid, const char *attname)
{
	HeapTuple	tuple,
				newtuple;

	tuple = SearchSysCacheAttName(relid, attname);
	if (!HeapTupleIsValid(tuple))
		return tuple;
	newtuple = heap_copytuple(tuple);
	ReleaseSysCache(tuple);
	return newtuple;
}

/*
 * SearchSysCacheExistsAttName
 *
 * As above, an attisdropped-aware version of SearchSysCacheExists.
 */
bool
SearchSysCacheExistsAttName(Oid relid, const char *attname)
{
	HeapTuple	tuple;

	tuple = SearchSysCacheAttName(relid, attname);
	if (!HeapTupleIsValid(tuple))
		return false;
	ReleaseSysCache(tuple);
	return true;
}


/*
 * SysCacheGetAttr
 *
 *		Given a tuple previously fetched by SearchSysCache(),
 *		extract a specific attribute.
 *
 * This is equivalent to using heap_getattr() on a tuple fetched
 * from a non-cached relation.	Usually, this is only used for attributes
 * that could be NULL or variable length; the fixed-size attributes in
 * a system table are accessed just by mapping the tuple onto the C struct
 * declarations from include/catalog/.
 *
 * As with heap_getattr(), if the attribute is of a pass-by-reference type
 * then a pointer into the tuple data area is returned --- the caller must
 * not modify or pfree the datum!
 */
Datum
SysCacheGetAttr(int cacheId, HeapTuple tup,
				AttrNumber attributeNumber,
				bool *isNull)
{
	/*
	 * We just need to get the TupleDesc out of the cache entry, and then
	 * we can apply heap_getattr().  We expect that the cache control data
	 * is currently valid --- if the caller recently fetched the tuple,
	 * then it should be.
	 */
	if (cacheId < 0 || cacheId >= SysCacheSize)
		elog(ERROR, "invalid cache id: %d", cacheId);
	if (!PointerIsValid(SysCache[cacheId]) ||
		!PointerIsValid(SysCache[cacheId]->cc_tupdesc))
		elog(ERROR, "missing cache data for cache id %d", cacheId);

	return heap_getattr(tup, attributeNumber,
						SysCache[cacheId]->cc_tupdesc,
						isNull);
}

/*
 * List-search interface
 */
struct catclist *
SearchSysCacheList(int cacheId, int nkeys,
				   Datum key1, Datum key2, Datum key3, Datum key4)
{
	if (cacheId < 0 || cacheId >= SysCacheSize ||
		!PointerIsValid(SysCache[cacheId]))
		elog(ERROR, "invalid cache id: %d", cacheId);

	return SearchCatCacheList(SysCache[cacheId], nkeys,
							  key1, key2, key3, key4);
}