relcache.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

/*-------------------------------------------------------------------------
 *
 * relcache.c
 *	  POSTGRES relation descriptor cache code
 *
 * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/utils/cache/relcache.c,v 1.230.2.3 2006/01/19 20:28:48 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
/*
 * INTERFACE ROUTINES
 *		RelationCacheInitialize			- initialize relcache
 *		RelationCacheInitializePhase2	- finish initializing relcache
 *		RelationIdGetRelation			- get a reldesc by relation id
 *		RelationIdCacheGetRelation		- get a cached reldesc by relid
 *		RelationClose					- close an open relation
 *
 * NOTES
 *		The following code contains many undocumented hacks.  Please be
 *		careful....
 */
#include "postgres.h"

#include <sys/file.h>
#include <fcntl.h>
#include <unistd.h>

#include "access/genam.h"
#include "access/heapam.h"
#include "catalog/catalog.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/pg_amop.h"
#include "catalog/pg_amproc.h"
#include "catalog/pg_attrdef.h"
#include "catalog/pg_attribute.h"
#include "catalog/pg_authid.h"
#include "catalog/pg_constraint.h"
#include "catalog/pg_index.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_opclass.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_rewrite.h"
#include "catalog/pg_type.h"
#include "commands/trigger.h"
#include "miscadmin.h"
#include "optimizer/clauses.h"
#include "optimizer/planmain.h"
#include "optimizer/prep.h"
#include "storage/fd.h"
#include "storage/smgr.h"
#include "utils/builtins.h"
#include "utils/catcache.h"
#include "utils/fmgroids.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/relcache.h"
#include "utils/resowner.h"
#include "utils/syscache.h"
#include "utils/typcache.h"


/*
 * name of relcache init file, used to speed up backend startup
 */
#define RELCACHE_INIT_FILENAME	"pg_internal.init"

#define RELCACHE_INIT_FILEMAGIC		0x573262	/* version ID value */

/*
 *		hardcoded tuple descriptors.  see include/catalog/pg_attribute.h
 */
static FormData_pg_attribute Desc_pg_class[Natts_pg_class] = {Schema_pg_class};
static FormData_pg_attribute Desc_pg_attribute[Natts_pg_attribute] = {Schema_pg_attribute};
static FormData_pg_attribute Desc_pg_proc[Natts_pg_proc] = {Schema_pg_proc};
static FormData_pg_attribute Desc_pg_type[Natts_pg_type] = {Schema_pg_type};
static FormData_pg_attribute Desc_pg_index[Natts_pg_index] = {Schema_pg_index};

/*
 *		Hash tables that index the relation cache
 *
 *		We used to index the cache by both name and OID, but now there
 *		is only an index by OID.
 */
typedef struct relidcacheent
{
	Oid			reloid;
	Relation	reldesc;
} RelIdCacheEnt;

static HTAB *RelationIdCache;

/*
 * This flag is false until we have prepared the critical relcache entries
 * that are needed to do indexscans on the tables read by relcache building.
 */
bool		criticalRelcachesBuilt = false;

/*
 * This flag is set if we discover that we need to write a new relcache
 * cache file at the end of startup.
 */
static bool needNewCacheFile = false;

/*
 * This counter counts relcache inval events received since backend startup
 * (but only for rels that are actually in cache).	Presently, we use it only
 * to detect whether data about to be written by write_relcache_init_file()
 * might already be obsolete.
 */
static long relcacheInvalsReceived = 0L;

/*
 * This list remembers the OIDs of the relations cached in the relcache
 * init file.
 */
static List *initFileRelationIds = NIL;

/*
 * This flag lets us optimize away work in AtEO(Sub)Xact_RelationCache().
 */
static bool need_eoxact_work = false;


/*
 *		macros to manipulate the lookup hashtables
 */
#define RelationCacheInsert(RELATION)	\
do { \
	RelIdCacheEnt *idhentry; bool found; \
	idhentry = (RelIdCacheEnt*)hash_search(RelationIdCache, \
										   (void *) &(RELATION->rd_id), \
										   HASH_ENTER, \
										   &found); \
	/* used to give notice if found -- now just keep quiet */ \
	idhentry->reldesc = RELATION; \
} while(0)

#define RelationIdCacheLookup(ID, RELATION) \
do { \
	RelIdCacheEnt *hentry; \
	hentry = (RelIdCacheEnt*)hash_search(RelationIdCache, \
										 (void *) &(ID), HASH_FIND,NULL); \
	if (hentry) \
		RELATION = hentry->reldesc; \
	else \
		RELATION = NULL; \
} while(0)

#define RelationCacheDelete(RELATION) \
do { \
	RelIdCacheEnt *idhentry; \
	idhentry = (RelIdCacheEnt*)hash_search(RelationIdCache, \
										   (void *) &(RELATION->rd_id), \
										   HASH_REMOVE, NULL); \
	if (idhentry == NULL) \
		elog(WARNING, "trying to delete a rd_id reldesc that does not exist"); \
} while(0)


/*
 * Special cache for opclass-related information
 *
 * Note: only default-subtype operators and support procs get cached
 */
typedef struct opclasscacheent
{
	Oid			opclassoid;		/* lookup key: OID of opclass */
	bool		valid;			/* set TRUE after successful fill-in */
	StrategyNumber numStrats;	/* max # of strategies (from pg_am) */
	StrategyNumber numSupport;	/* max # of support procs (from pg_am) */
	Oid		   *operatorOids;	/* strategy operators' OIDs */
	RegProcedure *supportProcs; /* support procs */
} OpClassCacheEnt;

static HTAB *OpClassCache = NULL;


/* non-export function prototypes */

static void RelationClearRelation(Relation relation, bool rebuild);

static void RelationReloadClassinfo(Relation relation);
static void RelationFlushRelation(Relation relation);
static bool load_relcache_init_file(void);
static void write_relcache_init_file(void);

static void formrdesc(const char *relationName, Oid relationReltype,
		  bool hasoids, int natts, FormData_pg_attribute *att);

static HeapTuple ScanPgRelation(Oid targetRelId, bool indexOK);
static Relation AllocateRelationDesc(Relation relation, Form_pg_class relp);
static void RelationBuildTupleDesc(Relation relation);
static Relation RelationBuildDesc(Oid targetRelId, Relation oldrelation);
static void RelationInitPhysicalAddr(Relation relation);
static TupleDesc GetPgIndexDescriptor(void);
static void AttrDefaultFetch(Relation relation);
static void CheckConstraintFetch(Relation relation);
static List *insert_ordered_oid(List *list, Oid datum);
static void IndexSupportInitialize(oidvector *indclass,
					   Oid *indexOperator,
					   RegProcedure *indexSupport,
					   StrategyNumber maxStrategyNumber,
					   StrategyNumber maxSupportNumber,
					   AttrNumber maxAttributeNumber);
static OpClassCacheEnt *LookupOpclassInfo(Oid operatorClassOid,
				  StrategyNumber numStrats,
				  StrategyNumber numSupport);


/*
 *		ScanPgRelation
 *
 *		this is used by RelationBuildDesc to find a pg_class
 *		tuple matching targetRelId.
 *
 *		NB: the returned tuple has been copied into palloc'd storage
 *		and must eventually be freed with heap_freetuple.
 */
static HeapTuple
ScanPgRelation(Oid targetRelId, bool indexOK)
{
	HeapTuple	pg_class_tuple;
	Relation	pg_class_desc;
	SysScanDesc pg_class_scan;
	ScanKeyData key[1];

	/*
	 * form a scan key
	 */
	ScanKeyInit(&key[0],
				ObjectIdAttributeNumber,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(targetRelId));

	/*
	 * Open pg_class and fetch a tuple.  Force heap scan if we haven't yet
	 * built the critical relcache entries (this includes initdb and startup
	 * without a pg_internal.init file).  The caller can also force a heap
	 * scan by setting indexOK == false.
	 */
	pg_class_desc = heap_open(RelationRelationId, AccessShareLock);
	pg_class_scan = systable_beginscan(pg_class_desc, ClassOidIndexId,
									   indexOK && criticalRelcachesBuilt,
									   SnapshotNow,
									   1, key);

	pg_class_tuple = systable_getnext(pg_class_scan);

	/*
	 * Must copy tuple before releasing buffer.
	 */
	if (HeapTupleIsValid(pg_class_tuple))
		pg_class_tuple = heap_copytuple(pg_class_tuple);

	/* all done */
	systable_endscan(pg_class_scan);
	heap_close(pg_class_desc, AccessShareLock);

	return pg_class_tuple;
}

/*
 *		AllocateRelationDesc
 *
 *		This is used to allocate memory for a new relation descriptor
 *		and initialize the rd_rel field.
 *
 *		If 'relation' is NULL, allocate a new RelationData object.
 *		If not, reuse the given object (that path is taken only when
 *		we have to rebuild a relcache entry during RelationClearRelation).
 */
static Relation
AllocateRelationDesc(Relation relation, Form_pg_class relp)
{
	MemoryContext oldcxt;
	Form_pg_class relationForm;

	/* Relcache entries must live in CacheMemoryContext */
	oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

	/*
	 * allocate space for new relation descriptor, if needed
	 */
	if (relation == NULL)
		relation = (Relation) palloc(sizeof(RelationData));

	/*
	 * clear all fields of reldesc
	 */
	MemSet(relation, 0, sizeof(RelationData));
	relation->rd_targblock = InvalidBlockNumber;

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

	/*
	 * Copy the relation tuple form
	 *
	 * We only allocate space for the fixed fields, ie, CLASS_TUPLE_SIZE.
	 * relacl is NOT stored in the relcache --- there'd be little point in it,
	 * since we don't copy the tuple's nullvalues bitmap and hence wouldn't
	 * know if the value is valid ... bottom line is that relacl *cannot* be
	 * retrieved from the relcache.  Get it from the syscache if you need it.
	 */
	relationForm = (Form_pg_class) palloc(CLASS_TUPLE_SIZE);

	memcpy(relationForm, relp, CLASS_TUPLE_SIZE);

	/* initialize relation tuple form */
	relation->rd_rel = relationForm;

	/* and allocate attribute tuple form storage */
	relation->rd_att = CreateTemplateTupleDesc(relationForm->relnatts,
											   relationForm->relhasoids);

	MemoryContextSwitchTo(oldcxt);

	return relation;
}

/*
 *		RelationBuildTupleDesc
 *
 *		Form the relation's tuple descriptor from information in
 *		the pg_attribute, pg_attrdef & pg_constraint system catalogs.
 */
static void
RelationBuildTupleDesc(Relation relation)
{
	HeapTuple	pg_attribute_tuple;
	Relation	pg_attribute_desc;
	SysScanDesc pg_attribute_scan;
	ScanKeyData skey[2];
	int			need;
	TupleConstr *constr;
	AttrDefault *attrdef = NULL;
	int			ndef = 0;

	/* copy some fields from pg_class row to rd_att */
	relation->rd_att->tdtypeid = relation->rd_rel->reltype;
	relation->rd_att->tdtypmod = -1;	/* unnecessary, but... */
	relation->rd_att->tdhasoid = relation->rd_rel->relhasoids;

	constr = (TupleConstr *) MemoryContextAlloc(CacheMemoryContext,
												sizeof(TupleConstr));
	constr->has_not_null = false;

	/*
	 * Form a scan key that selects only user attributes (attnum > 0).
	 * (Eliminating system attribute rows at the index level is lots faster
	 * than fetching them.)
	 */
	ScanKeyInit(&skey[0],
				Anum_pg_attribute_attrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(relation)));
	ScanKeyInit(&skey[1],
				Anum_pg_attribute_attnum,
				BTGreaterStrategyNumber, F_INT2GT,
				Int16GetDatum(0));

	/*
	 * Open pg_attribute and begin a scan.	Force heap scan if we haven't yet
	 * built the critical relcache entries (this includes initdb and startup
	 * without a pg_internal.init file).
	 */
	pg_attribute_desc = heap_open(AttributeRelationId, AccessShareLock);
	pg_attribute_scan = systable_beginscan(pg_attribute_desc,
										   AttributeRelidNumIndexId,
										   criticalRelcachesBuilt,
										   SnapshotNow,
										   2, skey);

	/*
	 * add attribute data to relation->rd_att
	 */
	need = relation->rd_rel->relnatts;

	while (HeapTupleIsValid(pg_attribute_tuple = systable_getnext(pg_attribute_scan)))
	{
		Form_pg_attribute attp;

		attp = (Form_pg_attribute) GETSTRUCT(pg_attribute_tuple);

		if (attp->attnum <= 0 ||
			attp->attnum > relation->rd_rel->relnatts)
			elog(ERROR, "invalid attribute number %d for %s",
				 attp->attnum, RelationGetRelationName(relation));

		memcpy(relation->rd_att->attrs[attp->attnum - 1],
			   attp,
			   ATTRIBUTE_TUPLE_SIZE);

		/* Update constraint/default info */
		if (attp->attnotnull)
			constr->has_not_null = true;

		if (attp->atthasdef)
		{
			if (attrdef == NULL)
				attrdef = (AttrDefault *)
					MemoryContextAllocZero(CacheMemoryContext,
										   relation->rd_rel->relnatts *
										   sizeof(AttrDefault));
			attrdef[ndef].adnum = attp->attnum;
			attrdef[ndef].adbin = NULL;
			ndef++;
		}
		need--;
		if (need == 0)
			break;
	}

	/*
	 * end the scan and close the attribute relation
	 */
	systable_endscan(pg_attribute_scan);
	heap_close(pg_attribute_desc, AccessShareLock);

	if (need != 0)
		elog(ERROR, "catalog is missing %d attribute(s) for relid %u",
			 need, RelationGetRelid(relation));

	/*
	 * The attcacheoff values we read from pg_attribute should all be -1
	 * ("unknown").  Verify this if assert checking is on.	They will be
	 * computed when and if needed during tuple access.
	 */
#ifdef USE_ASSERT_CHECKING
	{
		int			i;

		for (i = 0; i < relation->rd_rel->relnatts; i++)
			Assert(relation->rd_att->attrs[i]->attcacheoff == -1);
	}
#endif

	/*
	 * However, we can easily set the attcacheoff value for the first
	 * attribute: it must be zero.	This eliminates the need for special cases
	 * for attnum=1 that used to exist in fastgetattr() and index_getattr().
	 */
	if (relation->rd_rel->relnatts > 0)