relcache.c

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/*-------------------------------------------------------------------------
 *
 * relcache.c
 *	  POSTGRES relation descriptor cache code
 *
 * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/utils/cache/relcache.c,v 1.266.2.4 2008/08/10 19:02:46 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
/*
 * INTERFACE ROUTINES
 *		RelationCacheInitialize			- initialize relcache (to empty)
 *		RelationCacheInitializePhase2	- finish initializing relcache
 *		RelationIdGetRelation			- get a reldesc by relation id
 *		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 "access/reloptions.h"
#include "access/xact.h"
#include "catalog/catalog.h"
#include "catalog/index.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_authid.h"
#include "catalog/pg_constraint.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 "optimizer/var.h"
#include "rewrite/rewriteDefine.h"
#include "storage/fd.h"
#include "storage/smgr.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/inval.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		0x573264	/* 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 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 operators and support procs get cached, ie, those with
 * lefttype = righttype = opcintype.
 */
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			opcfamily;		/* OID of opclass's family */
	Oid			opcintype;		/* OID of opclass's declared input type */
	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 RelationReloadIndexInfo(Relation relation);
static void RelationFlushRelation(Relation relation);
static bool load_relcache_init_file(void);
static void write_relcache_init_file(void);
static void write_item(const void *data, Size len, FILE *fp);

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 RelationParseRelOptions(Relation relation, HeapTuple tuple);
static void RelationBuildTupleDesc(Relation relation);
static Relation RelationBuildDesc(Oid targetRelId, Relation oldrelation);
static void RelationInitPhysicalAddr(Relation relation);
static TupleDesc GetPgClassDescriptor(void);
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,
					   Oid *opFamily,
					   Oid *opcInType,
					   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.  The caller must hold at least
 *		AccessShareLock on the target relid to prevent concurrent-update
 *		scenarios --- else our SnapshotNow scan might fail to find any
 *		version that it thinks is live.
 *
 *		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. The
	 * variable-length fields (relacl, reloptions) are NOT stored in the
	 * relcache --- there'd be little point in it, since we don't copy the
	 * tuple's nulls bitmap and hence wouldn't know if the values are valid.
	 * Bottom line is that relacl *cannot* be retrieved from the relcache. Get
	 * it from the syscache if you need it.  The same goes for the original
	 * form of reloptions (however, we do store the parsed form of reloptions
	 * in rd_options).
	 */
	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);
	/* which we mark as a reference-counted tupdesc */
	relation->rd_att->tdrefcount = 1;

	MemoryContextSwitchTo(oldcxt);

	return relation;
}

/*
 * RelationParseRelOptions
 *		Convert pg_class.reloptions into pre-parsed rd_options
 *
 * tuple is the real pg_class tuple (not rd_rel!) for relation
 *
 * Note: rd_rel and (if an index) rd_am must be valid already
 */
static void
RelationParseRelOptions(Relation relation, HeapTuple tuple)
{
	Datum		datum;
	bool		isnull;
	bytea	   *options;

	relation->rd_options = NULL;

	/* Fall out if relkind should not have options */
	switch (relation->rd_rel->relkind)
	{
		case RELKIND_RELATION:
		case RELKIND_TOASTVALUE:
		case RELKIND_UNCATALOGED:
		case RELKIND_INDEX:
			break;
		default:
			return;
	}

	/*
	 * Fetch reloptions from tuple; have to use a hardwired descriptor because
	 * we might not have any other for pg_class yet (consider executing this
	 * code for pg_class itself)
	 */
	datum = fastgetattr(tuple,
						Anum_pg_class_reloptions,
						GetPgClassDescriptor(),
						&isnull);
	if (isnull)
		return;

	/* Parse into appropriate format; don't error out here */
	switch (relation->rd_rel->relkind)
	{
		case RELKIND_RELATION:
		case RELKIND_TOASTVALUE:
		case RELKIND_UNCATALOGED:
			options = heap_reloptions(relation->rd_rel->relkind, datum,
									  false);
			break;
		case RELKIND_INDEX:
			options = index_reloptions(relation->rd_am->amoptions, datum,
									   false);
			break;
		default:
			Assert(false);		/* can't get here */
			options = NULL;		/* keep compiler quiet */
			break;
	}

	/* Copy parsed data into CacheMemoryContext */
	if (options)
	{
		relation->rd_options = MemoryContextAlloc(CacheMemoryContext,
												  VARSIZE(options));
		memcpy(relation->rd_options, options, VARSIZE(options));
	}
}

/*
 *		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... */