relcache.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

					rebuildFirstList = lcons(relation, rebuildFirstList);
				else
					rebuildFirstList = lappend(rebuildFirstList, relation);
			}
			else
				rebuildList = lcons(relation, rebuildList);
		}
	}

	/*
	 * Now zap any remaining smgr cache entries.  This must happen before we
	 * start to rebuild entries, since that may involve catalog fetches which
	 * will re-open catalog files.
	 */
	smgrcloseall();

	/* Phase 2: rebuild the items found to need rebuild in phase 1 */
	foreach(l, rebuildFirstList)
	{
		relation = (Relation) lfirst(l);
		RelationClearRelation(relation, true);
	}
	list_free(rebuildFirstList);
	foreach(l, rebuildList)
	{
		relation = (Relation) lfirst(l);
		RelationClearRelation(relation, true);
	}
	list_free(rebuildList);
}

/*
 * AtEOXact_RelationCache
 *
 *	Clean up the relcache at main-transaction commit or abort.
 *
 * Note: this must be called *before* processing invalidation messages.
 * In the case of abort, we don't want to try to rebuild any invalidated
 * cache entries (since we can't safely do database accesses).  Therefore
 * we must reset refcnts before handling pending invalidations.
 *
 * As of PostgreSQL 8.1, relcache refcnts should get released by the
 * ResourceOwner mechanism.  This routine just does a debugging
 * cross-check that no pins remain.  However, we also need to do special
 * cleanup when the current transaction created any relations or made use
 * of forced index lists.
 */
void
AtEOXact_RelationCache(bool isCommit)
{
	HASH_SEQ_STATUS status;
	RelIdCacheEnt *idhentry;

	/*
	 * To speed up transaction exit, we want to avoid scanning the relcache
	 * unless there is actually something for this routine to do.  Other than
	 * the debug-only Assert checks, most transactions don't create any work
	 * for us to do here, so we keep a static flag that gets set if there is
	 * anything to do.	(Currently, this means either a relation is created in
	 * the current xact, or an index list is forced.)  For simplicity, the
	 * flag remains set till end of top-level transaction, even though we
	 * could clear it at subtransaction end in some cases.
	 */
	if (!need_eoxact_work
#ifdef USE_ASSERT_CHECKING
		&& !assert_enabled
#endif
		)
		return;

	hash_seq_init(&status, RelationIdCache);

	while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
	{
		Relation	relation = idhentry->reldesc;

		/*
		 * The relcache entry's ref count should be back to its normal
		 * not-in-a-transaction state: 0 unless it's nailed in cache.
		 *
		 * In bootstrap mode, this is NOT true, so don't check it --- the
		 * bootstrap code expects relations to stay open across start/commit
		 * transaction calls.  (That seems bogus, but it's not worth fixing.)
		 */
#ifdef USE_ASSERT_CHECKING
		if (!IsBootstrapProcessingMode())
		{
			int			expected_refcnt;

			expected_refcnt = relation->rd_isnailed ? 1 : 0;
			Assert(relation->rd_refcnt == expected_refcnt);
		}
#endif

		/*
		 * Is it a relation created in the current transaction?
		 *
		 * During commit, reset the flag to zero, since we are now out of the
		 * creating transaction.  During abort, simply delete the relcache
		 * entry --- it isn't interesting any longer.  (NOTE: if we have
		 * forgotten the new-ness of a new relation due to a forced cache
		 * flush, the entry will get deleted anyway by shared-cache-inval
		 * processing of the aborted pg_class insertion.)
		 */
		if (relation->rd_createSubid != InvalidSubTransactionId)
		{
			if (isCommit)
				relation->rd_createSubid = InvalidSubTransactionId;
			else
			{
				RelationClearRelation(relation, false);
				continue;
			}
		}

		/*
		 * Flush any temporary index list.
		 */
		if (relation->rd_indexvalid == 2)
		{
			list_free(relation->rd_indexlist);
			relation->rd_indexlist = NIL;
			relation->rd_oidindex = InvalidOid;
			relation->rd_indexvalid = 0;
		}
	}

	/* Once done with the transaction, we can reset need_eoxact_work */
	need_eoxact_work = false;
}

/*
 * AtEOSubXact_RelationCache
 *
 *	Clean up the relcache at sub-transaction commit or abort.
 *
 * Note: this must be called *before* processing invalidation messages.
 */
void
AtEOSubXact_RelationCache(bool isCommit, SubTransactionId mySubid,
						  SubTransactionId parentSubid)
{
	HASH_SEQ_STATUS status;
	RelIdCacheEnt *idhentry;

	/*
	 * Skip the relcache scan if nothing to do --- see notes for
	 * AtEOXact_RelationCache.
	 */
	if (!need_eoxact_work)
		return;

	hash_seq_init(&status, RelationIdCache);

	while ((idhentry = (RelIdCacheEnt *) hash_seq_search(&status)) != NULL)
	{
		Relation	relation = idhentry->reldesc;

		/*
		 * Is it a relation created in the current subtransaction?
		 *
		 * During subcommit, mark it as belonging to the parent, instead.
		 * During subabort, simply delete the relcache entry.
		 */
		if (relation->rd_createSubid == mySubid)
		{
			if (isCommit)
				relation->rd_createSubid = parentSubid;
			else
			{
				Assert(RelationHasReferenceCountZero(relation));
				RelationClearRelation(relation, false);
				continue;
			}
		}

		/*
		 * Flush any temporary index list.
		 */
		if (relation->rd_indexvalid == 2)
		{
			list_free(relation->rd_indexlist);
			relation->rd_indexlist = NIL;
			relation->rd_oidindex = InvalidOid;
			relation->rd_indexvalid = 0;
		}
	}
}

/*
 *		RelationBuildLocalRelation
 *			Build a relcache entry for an about-to-be-created relation,
 *			and enter it into the relcache.
 */
Relation
RelationBuildLocalRelation(const char *relname,
						   Oid relnamespace,
						   TupleDesc tupDesc,
						   Oid relid,
						   Oid reltablespace,
						   bool shared_relation)
{
	Relation	rel;
	MemoryContext oldcxt;
	int			natts = tupDesc->natts;
	int			i;
	bool		has_not_null;
	bool		nailit;

	AssertArg(natts >= 0);

	/*
	 * check for creation of a rel that must be nailed in cache.
	 *
	 * XXX this list had better match RelationCacheInitialize's list.
	 */
	switch (relid)
	{
		case RelationRelationId:
		case AttributeRelationId:
		case ProcedureRelationId:
		case TypeRelationId:
			nailit = true;
			break;
		default:
			nailit = false;
			break;
	}

	/*
	 * switch to the cache context to create the relcache entry.
	 */
	if (!CacheMemoryContext)
		CreateCacheMemoryContext();

	oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

	/*
	 * allocate a new relation descriptor and fill in basic state fields.
	 */
	rel = (Relation) palloc0(sizeof(RelationData));

	rel->rd_targblock = InvalidBlockNumber;

	/* make sure relation is marked as having no open file yet */
	rel->rd_smgr = NULL;

	/* mark it nailed if appropriate */
	rel->rd_isnailed = nailit;

	rel->rd_refcnt = nailit ? 1 : 0;

	/* it's being created in this transaction */
	rel->rd_createSubid = GetCurrentSubTransactionId();

	/* must flag that we have rels created in this transaction */
	need_eoxact_work = true;

	/* is it a temporary relation? */
	rel->rd_istemp = isTempNamespace(relnamespace);

	/*
	 * create a new tuple descriptor from the one passed in.  We do this
	 * partly to copy it into the cache context, and partly because the new
	 * relation can't have any defaults or constraints yet; they have to be
	 * added in later steps, because they require additions to multiple system
	 * catalogs.  We can copy attnotnull constraints here, however.
	 */
	rel->rd_att = CreateTupleDescCopy(tupDesc);
	has_not_null = false;
	for (i = 0; i < natts; i++)
	{
		rel->rd_att->attrs[i]->attnotnull = tupDesc->attrs[i]->attnotnull;
		has_not_null |= tupDesc->attrs[i]->attnotnull;
	}

	if (has_not_null)
	{
		TupleConstr *constr = (TupleConstr *) palloc0(sizeof(TupleConstr));

		constr->has_not_null = true;
		rel->rd_att->constr = constr;
	}

	/*
	 * initialize relation tuple form (caller may add/override data later)
	 */
	rel->rd_rel = (Form_pg_class) palloc0(CLASS_TUPLE_SIZE);

	namestrcpy(&rel->rd_rel->relname, relname);
	rel->rd_rel->relnamespace = relnamespace;

	rel->rd_rel->relkind = RELKIND_UNCATALOGED;
	rel->rd_rel->relhasoids = rel->rd_att->tdhasoid;
	rel->rd_rel->relnatts = natts;
	rel->rd_rel->reltype = InvalidOid;
	/* needed when bootstrapping: */
	rel->rd_rel->relowner = BOOTSTRAP_SUPERUSERID;

	/*
	 * Insert relation physical and logical identifiers (OIDs) into the right
	 * places.	Note that the physical ID (relfilenode) is initially the same
	 * as the logical ID (OID).
	 */
	rel->rd_rel->relisshared = shared_relation;

	RelationGetRelid(rel) = relid;

	for (i = 0; i < natts; i++)
		rel->rd_att->attrs[i]->attrelid = relid;

	rel->rd_rel->relfilenode = relid;
	rel->rd_rel->reltablespace = reltablespace;

	RelationInitLockInfo(rel);	/* see lmgr.c */

	RelationInitPhysicalAddr(rel);

	/*
	 * Okay to insert into the relcache hash tables.
	 */
	RelationCacheInsert(rel);

	/*
	 * done building relcache entry.
	 */
	MemoryContextSwitchTo(oldcxt);

	/* It's fully valid */
	rel->rd_isvalid = true;

	/*
	 * Caller expects us to pin the returned entry.
	 */
	RelationIncrementReferenceCount(rel);

	return rel;
}

/*
 *		RelationCacheInitialize
 *
 *		This initializes the relation descriptor cache.  At the time
 *		that this is invoked, we can't do database access yet (mainly
 *		because the transaction subsystem is not up), so we can't get
 *		"real" info.  However it's okay to read the pg_internal.init
 *		cache file, if one is available.  Otherwise we make phony
 *		entries for the minimum set of nailed-in-cache relations.
 */

#define INITRELCACHESIZE		400

void
RelationCacheInitialize(void)
{
	MemoryContext oldcxt;
	HASHCTL		ctl;

	/*
	 * switch to cache memory context
	 */
	if (!CacheMemoryContext)
		CreateCacheMemoryContext();

	oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

	/*
	 * create hashtables that index the relcache
	 */
	MemSet(&ctl, 0, sizeof(ctl));
	ctl.keysize = sizeof(Oid);
	ctl.entrysize = sizeof(RelIdCacheEnt);
	ctl.hash = oid_hash;
	RelationIdCache = hash_create("Relcache by OID", INITRELCACHESIZE,
								  &ctl, HASH_ELEM | HASH_FUNCTION);

	/*
	 * Try to load the relcache cache file.  If successful, we're done for
	 * now.  Otherwise, initialize the cache with pre-made descriptors for the
	 * critical "nailed-in" system catalogs.
	 */
	if (IsBootstrapProcessingMode() ||
		!load_relcache_init_file())
	{
		formrdesc("pg_class", PG_CLASS_RELTYPE_OID,
				  true, Natts_pg_class, Desc_pg_class);
		formrdesc("pg_attribute", PG_ATTRIBUTE_RELTYPE_OID,
				  false, Natts_pg_attribute, Desc_pg_attribute);
		formrdesc("pg_proc", PG_PROC_RELTYPE_OID,
				  true, Natts_pg_proc, Desc_pg_proc);
		formrdesc("pg_type", PG_TYPE_RELTYPE_OID,
				  true, Natts_pg_type, Desc_pg_type);

#define NUM_CRITICAL_RELS	4	/* fix if you change list above */
	}

	MemoryContextSwitchTo(oldcxt);
}

/*
 *		RelationCacheInitializePhase2
 *
 *		This is called as soon as the catcache and transaction system
 *		are functional.  At this point we can actually read data from
 *		the system catalogs.  Update the relcache entries made during
 *		RelationCacheInitialize, and make sure we have entries for the
 *		critical system indexes.
 */
void
RelationCacheInitializePhase2(void)
{
	HASH_SEQ_STATUS status;
	RelIdCacheEnt *idhentry;

	if (IsBootstrapProcessingMode())
		return;

	/*
	 * If we didn't get the critical system indexes loaded into relcache, do
	 * so now.	These are critical because the catcache depends on them for
	 * catcache fetches that are done during relcache load.  Thus, we have an
	 * infinite-recursion problem.	We can break the recursion by doing
	 * heapscans instead of indexscans at certain key spots. To avoid hobbling
	 * performance, we only want to do that until we have the critical indexes
	 * loaded into relcache.  Thus, the flag criticalRelcachesBuilt is used to
	 * decide whether to do heapscan or indexscan at the key spots, and we set
	 * it true after we've loaded the critical indexes.
	 *
	 * The critical indexes are marked as "nailed in cache", partly to make it
	 * easy for load_relcache_init_file to count them, but mainly because we
	 * cannot flush and rebuild them once we've set criticalRelcachesBuilt to
	 * true.  (NOTE: perhaps it would be possible to reload them by
	 * temporarily setting criticalRelcachesBuilt to false again.  For now,
	 * though, we just nail 'em in.)
	 */
	if (!criticalRelcachesBuilt)
	{
		Relation	ird;

#define LOAD_CRIT_INDEX(indexoid) \
		do { \
			ird = RelationBuildDesc((indexoid), NULL); \
			ird->rd_isnailed = true; \
			ird->rd_refcnt = 1; \
		} while (0)

		LOAD_CRIT_INDEX(ClassOidIndexId);
		LOAD_CRIT_INDEX(AttributeRelidNumIndexId);
		LOAD_CRIT_INDEX(IndexRelidIndexI