indexam.c

postgresql8.3.4源码,开源数据库

/*-------------------------------------------------------------------------
 *
 * indexam.c
 *	  general index access method routines
 *
 * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/access/index/indexam.c,v 1.101.2.1 2008/09/11 14:01:35 alvherre Exp $
 *
 * INTERFACE ROUTINES
 *		index_open		- open an index relation by relation OID
 *		index_close		- close an index relation
 *		index_beginscan - start a scan of an index with amgettuple
 *		index_beginscan_multi - start a scan of an index with amgetmulti
 *		index_rescan	- restart a scan of an index
 *		index_endscan	- end a scan
 *		index_insert	- insert an index tuple into a relation
 *		index_markpos	- mark a scan position
 *		index_restrpos	- restore a scan position
 *		index_getnext	- get the next tuple from a scan
 *		index_getmulti	- get multiple tuples from a scan
 *		index_bulk_delete	- bulk deletion of index tuples
 *		index_vacuum_cleanup	- post-deletion cleanup of an index
 *		index_getprocid - get a support procedure OID
 *		index_getprocinfo - get a support procedure's lookup info
 *
 * NOTES
 *		This file contains the index_ routines which used
 *		to be a scattered collection of stuff in access/genam.
 *
 *
 * old comments
 *		Scans are implemented as follows:
 *
 *		`0' represents an invalid item pointer.
 *		`-' represents an unknown item pointer.
 *		`X' represents a known item pointers.
 *		`+' represents known or invalid item pointers.
 *		`*' represents any item pointers.
 *
 *		State is represented by a triple of these symbols in the order of
 *		previous, current, next.  Note that the case of reverse scans works
 *		identically.
 *
 *				State	Result
 *		(1)		+ + -	+ 0 0			(if the next item pointer is invalid)
 *		(2)				+ X -			(otherwise)
 *		(3)		* 0 0	* 0 0			(no change)
 *		(4)		+ X 0	X 0 0			(shift)
 *		(5)		* + X	+ X -			(shift, add unknown)
 *
 *		All other states cannot occur.
 *
 *		Note: It would be possible to cache the status of the previous and
 *			  next item pointer using the flags.
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "access/genam.h"
#include "access/heapam.h"
#include "access/transam.h"
#include "pgstat.h"
#include "utils/relcache.h"


/* ----------------------------------------------------------------
 *					macros used in index_ routines
 * ----------------------------------------------------------------
 */
#define RELATION_CHECKS \
( \
	AssertMacro(RelationIsValid(indexRelation)), \
	AssertMacro(PointerIsValid(indexRelation->rd_am)) \
)

#define SCAN_CHECKS \
( \
	AssertMacro(IndexScanIsValid(scan)), \
	AssertMacro(RelationIsValid(scan->indexRelation)), \
	AssertMacro(PointerIsValid(scan->indexRelation->rd_am)) \
)

#define GET_REL_PROCEDURE(pname) \
do { \
	procedure = &indexRelation->rd_aminfo->pname; \
	if (!OidIsValid(procedure->fn_oid)) \
	{ \
		RegProcedure	procOid = indexRelation->rd_am->pname; \
		if (!RegProcedureIsValid(procOid)) \
			elog(ERROR, "invalid %s regproc", CppAsString(pname)); \
		fmgr_info_cxt(procOid, procedure, indexRelation->rd_indexcxt); \
	} \
} while(0)

#define GET_SCAN_PROCEDURE(pname) \
do { \
	procedure = &scan->indexRelation->rd_aminfo->pname; \
	if (!OidIsValid(procedure->fn_oid)) \
	{ \
		RegProcedure	procOid = scan->indexRelation->rd_am->pname; \
		if (!RegProcedureIsValid(procOid)) \
			elog(ERROR, "invalid %s regproc", CppAsString(pname)); \
		fmgr_info_cxt(procOid, procedure, scan->indexRelation->rd_indexcxt); \
	} \
} while(0)

static IndexScanDesc index_beginscan_internal(Relation indexRelation,
						 int nkeys, ScanKey key);


/* ----------------------------------------------------------------
 *				   index_ interface functions
 * ----------------------------------------------------------------
 */

/* ----------------
 *		index_open - open an index relation by relation OID
 *
 *		If lockmode is not "NoLock", the specified kind of lock is
 *		obtained on the index.	(Generally, NoLock should only be
 *		used if the caller knows it has some appropriate lock on the
 *		index already.)
 *
 *		An error is raised if the index does not exist.
 *
 *		This is a convenience routine adapted for indexscan use.
 *		Some callers may prefer to use relation_open directly.
 * ----------------
 */
Relation
index_open(Oid relationId, LOCKMODE lockmode)
{
	Relation	r;

	r = relation_open(relationId, lockmode);

	if (r->rd_rel->relkind != RELKIND_INDEX)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("\"%s\" is not an index",
						RelationGetRelationName(r))));

	return r;
}

/* ----------------
 *		index_close - close an index relation
 *
 *		If lockmode is not "NoLock", we then release the specified lock.
 *
 *		Note that it is often sensible to hold a lock beyond index_close;
 *		in that case, the lock is released automatically at xact end.
 * ----------------
 */
void
index_close(Relation relation, LOCKMODE lockmode)
{
	LockRelId	relid = relation->rd_lockInfo.lockRelId;

	Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES);

	/* The relcache does the real work... */
	RelationClose(relation);

	if (lockmode != NoLock)
		UnlockRelationId(&relid, lockmode);
}

/* ----------------
 *		index_insert - insert an index tuple into a relation
 * ----------------
 */
bool
index_insert(Relation indexRelation,
			 Datum *values,
			 bool *isnull,
			 ItemPointer heap_t_ctid,
			 Relation heapRelation,
			 bool check_uniqueness)
{
	FmgrInfo   *procedure;

	RELATION_CHECKS;
	GET_REL_PROCEDURE(aminsert);

	/*
	 * have the am's insert proc do all the work.
	 */
	return DatumGetBool(FunctionCall6(procedure,
									  PointerGetDatum(indexRelation),
									  PointerGetDatum(values),
									  PointerGetDatum(isnull),
									  PointerGetDatum(heap_t_ctid),
									  PointerGetDatum(heapRelation),
									  BoolGetDatum(check_uniqueness)));
}

/*
 * index_beginscan - start a scan of an index with amgettuple
 *
 * Note: heapRelation may be NULL if there is no intention of calling
 * index_getnext on this scan; index_getnext_indexitem will not use the
 * heapRelation link (nor the snapshot).  However, the caller had better
 * be holding some kind of lock on the heap relation in any case, to ensure
 * no one deletes it (or the index) out from under us.	Caller must also
 * be holding a lock on the index.
 */
IndexScanDesc
index_beginscan(Relation heapRelation,
				Relation indexRelation,
				Snapshot snapshot,
				int nkeys, ScanKey key)
{
	IndexScanDesc scan;

	scan = index_beginscan_internal(indexRelation, nkeys, key);

	/*
	 * Save additional parameters into the scandesc.  Everything else was set
	 * up by RelationGetIndexScan.
	 */
	scan->is_multiscan = false;
	scan->heapRelation = heapRelation;
	scan->xs_snapshot = snapshot;

	return scan;
}

/*
 * index_beginscan_multi - start a scan of an index with amgetmulti
 *
 * As above, caller had better be holding some lock on the parent heap
 * relation, even though it's not explicitly mentioned here.
 */
IndexScanDesc
index_beginscan_multi(Relation indexRelation,
					  Snapshot snapshot,
					  int nkeys, ScanKey key)
{
	IndexScanDesc scan;

	scan = index_beginscan_internal(indexRelation, nkeys, key);

	/*
	 * Save additional parameters into the scandesc.  Everything else was set
	 * up by RelationGetIndexScan.
	 */
	scan->is_multiscan = true;
	scan->xs_snapshot = snapshot;

	return scan;
}

/*
 * index_beginscan_internal --- common code for index_beginscan variants
 */
static IndexScanDesc
index_beginscan_internal(Relation indexRelation,
						 int nkeys, ScanKey key)
{
	IndexScanDesc scan;
	FmgrInfo   *procedure;

	RELATION_CHECKS;
	GET_REL_PROCEDURE(ambeginscan);

	/*
	 * We hold a reference count to the relcache entry throughout the scan.
	 */
	RelationIncrementReferenceCount(indexRelation);

	/*
	 * Tell the AM to open a scan.
	 */
	scan = (IndexScanDesc)
		DatumGetPointer(FunctionCall3(procedure,
									  PointerGetDatum(indexRelation),
									  Int32GetDatum(nkeys),
									  PointerGetDatum(key)));

	return scan;
}

/* ----------------
 *		index_rescan  - (re)start a scan of an index
 *
 * The caller may specify a new set of scankeys (but the number of keys
 * cannot change).	To restart the scan without changing keys, pass NULL
 * for the key array.
 *
 * Note that this is also called when first starting an indexscan;
 * see RelationGetIndexScan.  Keys *must* be passed in that case,
 * unless scan->numberOfKeys is zero.
 * ----------------
 */
void
index_rescan(IndexScanDesc scan, ScanKey key)
{
	FmgrInfo   *procedure;

	SCAN_CHECKS;
	GET_SCAN_PROCEDURE(amrescan);

	/* Release any held pin on a heap page */
	if (BufferIsValid(scan->xs_cbuf))
	{
		ReleaseBuffer(scan->xs_cbuf);
		scan->xs_cbuf = InvalidBuffer;
	}

	scan->xs_next_hot = InvalidOffsetNumber;

	scan->kill_prior_tuple = false;		/* for safety */

	FunctionCall2(procedure,
				  PointerGetDatum(scan),
				  PointerGetDatum(key));
}

/* ----------------
 *		index_endscan - end a scan
 * ----------------
 */
void
index_endscan(IndexScanDesc scan)
{
	FmgrInfo   *procedure;

	SCAN_CHECKS;
	GET_SCAN_PROCEDURE(amendscan);

	/* Release any held pin on a heap page */
	if (BufferIsValid(scan->xs_cbuf))
	{
		ReleaseBuffer(scan->xs_cbuf);
		scan->xs_cbuf = InvalidBuffer;
	}

	/* End the AM's scan */
	FunctionCall1(procedure, PointerGetDatum(scan));

	/* Release index refcount acquired by index_beginscan */
	RelationDecrementReferenceCount(scan->indexRelation);

	/* Release the scan data structure itself */
	IndexScanEnd(scan);
}

/* ----------------
 *		index_markpos  - mark a scan position
 * ----------------
 */
void
index_markpos(IndexScanDesc scan)
{
	FmgrInfo   *procedure;

	SCAN_CHECKS;
	GET_SCAN_PROCEDURE(ammarkpos);

	FunctionCall1(procedure, PointerGetDatum(scan));
}

/* ----------------
 *		index_restrpos	- restore a scan position
 *
 * NOTE: this only restores the internal scan state of the index AM.
 * The current result tuple (scan->xs_ctup) doesn't change.  See comments
 * for ExecRestrPos().
 *
 * NOTE: in the presence of HOT chains, mark/restore only works correctly
 * if the scan's snapshot is MVCC-safe; that ensures that there's at most one
 * returnable tuple in each HOT chain, and so restoring the prior state at the
 * granularity of the index AM is sufficient.  Since the only current user
 * of mark/restore functionality is nodeMergejoin.c, this effectively means
 * that merge-join plans only work for MVCC snapshots.	This could be fixed
 * if necessary, but for now it seems unimportant.
 * ----------------
 */
void
index_restrpos(IndexScanDesc scan)
{
	FmgrInfo   *procedure;

	Assert(IsMVCCSnapshot(scan->xs_snapshot));

	SCAN_CHECKS;
	GET_SCAN_PROCEDURE(amrestrpos);

	scan->xs_next_hot = InvalidOffsetNumber;

	scan->kill_prior_tuple = false;		/* for safety */

	FunctionCall1(procedure, PointerGetDatum(scan));
}

/* ----------------
 *		index_getnext - get the next heap tuple from a scan
 *
 * The result is the next heap tuple satisfying the scan keys and the
 * snapshot, or NULL if no more matching tuples exist.	On success,
 * the buffer containing the heap tuple is pinned (the pin will be dropped
 * at the next index_getnext or index_endscan).
 * ----------------
 */
HeapTuple
index_getnext(IndexScanDesc scan, ScanDirection direction)
{
	HeapTuple	heapTuple = &scan->xs_ctup;
	ItemPointer tid = &heapTuple->t_self;
	FmgrInfo   *procedure;

	SCAN_CHECKS;
	GET_SCAN_PROCEDURE(amgettuple);

	Assert(TransactionIdIsValid(RecentGlobalXmin));

	/*
	 * We always reset xs_hot_dead; if we are here then either we are just
	 * starting the scan, or we previously returned a visible tuple, and in
	 * either case it's inappropriate to kill the prior index entry.
	 */
	scan->xs_hot_dead = false;

	for (;;)
	{
		OffsetNumber offnum;
		bool		at_chain_start;
		Page		dp;

		if (scan->xs_next_hot != InvalidOffsetNumber)
		{
			/*
			 * We are resuming scan of a HOT chain after having returned an
			 * earlier member.	Must still hold pin on current heap page.