nodeindexscan.c

关系型数据库 Postgresql 6.5.2

/*-------------------------------------------------------------------------
 *
 * nodeIndexscan.c
 *	  Routines to support indexes and indexed scans of relations
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $Header: /usr/local/cvsroot/pgsql/src/backend/executor/nodeIndexscan.c,v 1.36 1999/05/25 16:08:43 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
/*
 * INTERFACE ROUTINES
 *		ExecInsertIndexTuples	inserts tuples into indices on result relation
 *
 *		ExecIndexScan			scans a relation using indices
 *		ExecIndexNext			using index to retrieve next tuple
 *		ExecInitIndexScan		creates and initializes state info.
 *		ExecIndexReScan			rescans the indexed relation.
 *		ExecEndIndexScan		releases all storage.
 *		ExecIndexMarkPos		marks scan position.
 *		ExecIndexRestrPos		restores scan position.
 *
 *	 NOTES
 *		the code supporting ExecInsertIndexTuples should be
 *		collected and merged with the genam stuff.
 *
 */
#include "postgres.h"

#include "executor/executor.h"
#include "executor/execdebug.h"
#include "executor/nodeIndexscan.h"

#include "optimizer/clauses.h"	/* for get_op, get_leftop, get_rightop */
#include "parser/parsetree.h"	/* for rt_fetch() */

#include "access/skey.h"
#include "access/heapam.h"
#include "access/genam.h"
#include "utils/palloc.h"
#include "utils/mcxt.h"
#include "catalog/index.h"
#include "storage/bufmgr.h"
#include "storage/lmgr.h"
#include "nodes/nodeFuncs.h"

/* ----------------
 *		Misc stuff to move to executor.h soon -cim 6/5/90
 * ----------------
 */
#define NO_OP			0
#define LEFT_OP			1
#define RIGHT_OP		2

static TupleTableSlot *IndexNext(IndexScan *node);

/* ----------------------------------------------------------------
 *		IndexNext
 *
 *		Retrieve a tuple from the IndexScan node's currentRelation
 *		using the indices in the IndexScanState information.
 *
 *		note: the old code mentions 'Primary indices'.	to my knowledge
 *		we only support a single secondary index. -cim 9/11/89
 *
 * old comments:
 *		retrieve a tuple from relation using the indices given.
 *		The indices are used in the order they appear in 'indices'.
 *		The indices may be primary or secondary indices:
 *		  * primary index --	scan the relation 'relID' using keys supplied.
 *		  * secondary index --	scan the index relation to get the 'tid' for
 *								a tuple in the relation 'relID'.
 *		If the current index(pointed by 'indexPtr') fails to return a
 *		tuple, the next index in the indices is used.
 *
 *		  bug fix so that it should retrieve on a null scan key.
 * ----------------------------------------------------------------
 */
static TupleTableSlot *
IndexNext(IndexScan *node)
{
	EState	   *estate;
	CommonScanState *scanstate;
	IndexScanState *indexstate;
	ScanDirection direction;
	Snapshot	snapshot;
	IndexScanDescPtr scanDescs;
	IndexScanDesc scandesc;
	Relation	heapRelation;
	RetrieveIndexResult result;
	HeapTuple	tuple;
	TupleTableSlot *slot;
	Buffer		buffer = InvalidBuffer;
	int			numIndices;

	bool		bBackward;
	int			indexNumber;

	/* ----------------
	 *	extract necessary information from index scan node
	 * ----------------
	 */
	estate = node->scan.plan.state;
	direction = estate->es_direction;
	snapshot = estate->es_snapshot;
	scanstate = node->scan.scanstate;
	indexstate = node->indxstate;
	scanDescs = indexstate->iss_ScanDescs;
	heapRelation = scanstate->css_currentRelation;
	numIndices = indexstate->iss_NumIndices;
	slot = scanstate->css_ScanTupleSlot;

	/*
	 * Check if we are evaluating PlanQual for tuple of this relation.
	 * Additional checking is not good, but no other way for now. We could
	 * introduce new nodes for this case and handle IndexScan --> NewNode
	 * switching in Init/ReScan plan...
	 */
	if (estate->es_evTuple != NULL &&
		estate->es_evTuple[node->scan.scanrelid - 1] != NULL)
	{
		int			iptr;

		slot->ttc_buffer = InvalidBuffer;
		slot->ttc_shouldFree = false;
		if (estate->es_evTupleNull[node->scan.scanrelid - 1])
		{
			slot->val = NULL;	/* must not free tuple! */
			return (slot);
		}
		slot->val = estate->es_evTuple[node->scan.scanrelid - 1];
		for (iptr = 0; iptr < numIndices; iptr++)
		{
			scanstate->cstate.cs_ExprContext->ecxt_scantuple = slot;
			if (ExecQual(nth(iptr, node->indxqualorig),
						 scanstate->cstate.cs_ExprContext))
				break;
		}
		if (iptr == numIndices) /* would not be returned by indices */
			slot->val = NULL;
		/* Flag for the next call that no more tuples */
		estate->es_evTupleNull[node->scan.scanrelid - 1] = true;
		return (slot);
	}

	tuple = &(indexstate->iss_htup);

	/* ----------------
	 *	ok, now that we have what we need, fetch an index tuple.
	 *	if scanning this index succeeded then return the
	 *	appropriate heap tuple.. else return NULL.
	 * ----------------
	 */
	bBackward = ScanDirectionIsBackward(direction);
	if (bBackward)
	{
		indexNumber = numIndices - indexstate->iss_IndexPtr - 1;
		if (indexNumber < 0)
		{
			indexNumber = 0;
			indexstate->iss_IndexPtr = numIndices - 1;
		}
	}
	else
	{
		if ((indexNumber = indexstate->iss_IndexPtr) < 0)
		{
			indexNumber = 0;
			indexstate->iss_IndexPtr = 0;
		}
	}
	while (indexNumber < numIndices)
	{
		scandesc = scanDescs[indexstate->iss_IndexPtr];
		while ((result = index_getnext(scandesc, direction)) != NULL)
		{
			tuple->t_self = result->heap_iptr;
			heap_fetch(heapRelation, snapshot, tuple, &buffer);
			pfree(result);

			if (tuple->t_data != NULL)
			{
				bool		prev_matches = false;
				int			prev_index;

				/* ----------------
				 *	store the scanned tuple in the scan tuple slot of
				 *	the scan state.  Eventually we will only do this and not
				 *	return a tuple.  Note: we pass 'false' because tuples
				 *	returned by amgetnext are pointers onto disk pages and
				 *	were not created with palloc() and so should not be pfree()'d.
				 * ----------------
				 */
				ExecStoreTuple(tuple,	/* tuple to store */
							   slot,	/* slot to store in */
							   buffer,	/* buffer associated with tuple  */
							   false);	/* don't pfree */

				/*
				 * We must check to see if the current tuple would have
				 * been matched by an earlier index, so we don't double
				 * report it. We do this by passing the tuple through
				 * ExecQual and look for failure with all previous
				 * qualifications.
				 */
				for (prev_index = 0; prev_index < indexstate->iss_IndexPtr;
					 prev_index++)
				{
					scanstate->cstate.cs_ExprContext->ecxt_scantuple = slot;
					if (ExecQual(nth(prev_index, node->indxqualorig),
								 scanstate->cstate.cs_ExprContext))
					{
						prev_matches = true;
						break;
					}
				}
				if (!prev_matches)
					return slot;
				else
					ExecClearTuple(slot);
			}
			if (BufferIsValid(buffer))
				ReleaseBuffer(buffer);
		}
		if (indexNumber < numIndices)
		{
			indexNumber++;
			if (bBackward)
				indexstate->iss_IndexPtr--;
			else
				indexstate->iss_IndexPtr++;
		}
	}
	/* ----------------
	 *	if we get here it means the index scan failed so we
	 *	are at the end of the scan..
	 * ----------------
	 */
	return ExecClearTuple(slot);
}

/* ----------------------------------------------------------------
 *		ExecIndexScan(node)
 *
 * old comments:
 *		Scans the relation using primary or secondary indices and returns
 *		   the next qualifying tuple in the direction specified.
 *		It calls ExecScan() and passes it the access methods which returns
 *		the next tuple using the indices.
 *
 *		Conditions:
 *		  -- the "cursor" maintained by the AMI is positioned at the tuple
 *			 returned previously.
 *
 *		Initial States:
 *		  -- the relation indicated is opened for scanning so that the
 *			 "cursor" is positioned before the first qualifying tuple.
 *		  -- all index realtions are opened for scanning.
 *		  -- indexPtr points to the first index.
 *		  -- state variable ruleFlag = nil.
 * ----------------------------------------------------------------
 */
TupleTableSlot *
ExecIndexScan(IndexScan *node)
{
	/* ----------------
	 *	use IndexNext as access method
	 * ----------------
	 */
	return ExecScan(&node->scan, IndexNext);
}

/* ----------------------------------------------------------------
 *		ExecIndexReScan(node)
 *
 *		Recalculates the value of the scan keys whose value depends on
 *		information known at runtime and rescans the indexed relation.
 *		Updating the scan key was formerly done separately in
 *		ExecUpdateIndexScanKeys. Integrating it into ReScan
 *		makes rescans of indices and
 *		relations/general streams more uniform.
 *
 * ----------------------------------------------------------------
 */
void
ExecIndexReScan(IndexScan *node, ExprContext *exprCtxt, Plan *parent)
{
	EState	   *estate;
	IndexScanState *indexstate;
	ScanDirection direction;
	IndexScanDescPtr scanDescs;
	ScanKey    *scanKeys;
	IndexScanDesc scan;
	ScanKey		skey;
	int			numIndices;
	int			i;

	Pointer    *runtimeKeyInfo;
	int		   *numScanKeys;
	List	   *indxqual;
	List	   *qual;
	int			n_keys;
	ScanKey		scan_keys;
	int		   *run_keys;
	int			j;
	Expr	   *clause;
	Node	   *scanexpr;
	Datum		scanvalue;
	bool		isNull;
	bool		isDone;

	indexstate = node->indxstate;
	estate = node->scan.plan.state;
	direction = estate->es_direction;
	numIndices = indexstate->iss_NumIndices;
	scanDescs = indexstate->iss_ScanDescs;
	scanKeys = indexstate->iss_ScanKeys;
	runtimeKeyInfo = (Pointer *) indexstate->iss_RuntimeKeyInfo;
	indxqual = node->indxqual;
	numScanKeys = indexstate->iss_NumScanKeys;
	indexstate->iss_IndexPtr = -1;

	/* If this is re-scanning of PlanQual ... */
	if (estate->es_evTuple != NULL &&
		estate->es_evTuple[node->scan.scanrelid - 1] != NULL)
	{
		estate->es_evTupleNull[node->scan.scanrelid - 1] = false;
		return;
	}

	/* it's possible in subselects */
	if (exprCtxt == NULL)
		exprCtxt = node->scan.scanstate->cstate.cs_ExprContext;

	node->scan.scanstate->cstate.cs_ExprContext->ecxt_outertuple = exprCtxt->ecxt_outertuple;

	/*
	 * get the index qualifications and recalculate the appropriate values
	 */
	for (i = 0; i < numIndices; i++)
	{
		qual = nth(i, indxqual);
		n_keys = numScanKeys[i];
		scan_keys = (ScanKey) scanKeys[i];

		if (runtimeKeyInfo)
		{
			run_keys = (int *) runtimeKeyInfo[i];
			for (j = 0; j < n_keys; j++)
			{

				/*
				 * If we have a run-time key, then extract the run-time
				 * expression and evaluate it with respect to the current
				 * outer tuple.  We then stick the result into the scan
				 * key.
				 */
				if (run_keys[j] != NO_OP)
				{
					clause = nth(j, qual);
					scanexpr = (run_keys[j] == RIGHT_OP) ?
						(Node *) get_rightop(clause) : (Node *) get_leftop(clause);

					/*
					 * pass in isDone but ignore it.  We don't iterate in
					 * quals
					 */
					scanvalue = (Datum)
						ExecEvalExpr(scanexpr, exprCtxt, &isNull, &isDone);
					scan_keys[j].sk_argument = scanvalue;
					if (isNull)
						scan_keys[j].sk_flags |= SK_ISNULL;
					else
						scan_keys[j].sk_flags &= ~SK_ISNULL;
				}
			}
		}
		scan = scanDescs[i];
		skey = scanKeys[i];
		index_rescan(scan, direction, skey);
	}
	/* ----------------
	 *	perhaps return something meaningful
	 * ----------------
	 */
	return;
}

/* ----------------------------------------------------------------
 *		ExecEndIndexScan
 *
 * old comments
 *		Releases any storage allocated through C routines.
 *		Returns nothing.
 * ----------------------------------------------------------------
 */
void
ExecEndIndexScan(IndexScan *node)
{
	CommonScanState *scanstate;
	IndexScanState *indexstate;
	Pointer    *runtimeKeyInfo;
	ScanKey    *scanKeys;
	List	   *indxqual;
	int		   *numScanKeys;
	int			numIndices;
	int			i;

	scanstate = node->scan.scanstate;
	indexstate = node->indxstate;
	indxqual = node->indxqual;
	runtimeKeyInfo = (Pointer *) indexstate->iss_RuntimeKeyInfo;

	/* ----------------
	 *	extract information from the node
	 * ----------------
	 */
	numIndices = indexstate->iss_NumIndices;
	scanKeys = indexstate->iss_ScanKeys;
	numScanKeys = indexstate->iss_NumScanKeys;

	/* ----------------
	 *	Free the projection info and the scan attribute info
	 *
	 *	Note: we don't ExecFreeResultType(scanstate)
	 *		  because the rule manager depends on the tupType
	 *		  returned by ExecMain().  So for now, this
	 *		  is freed at end-transaction time.  -cim 6/2/91
	 * ----------------
	 */
	ExecFreeProjectionInfo(&scanstate->cstate);

	/* ----------------
	 *	close the heap and index relations
	 * ----------------
	 */
	ExecCloseR((Plan *) node);

	/* ----------------
	 *	free the scan keys used in scanning the indices
	 * ----------------
	 */
	for (i = 0; i < numIndices; i++)
	{
		if (scanKeys[i] != NULL)
			pfree(scanKeys[i]);
	}
	pfree(scanKeys);
	pfree(numScanKeys);

	if (runtimeKeyInfo)
	{
		for (i = 0; i < numIndices; i++)
		{
			List	   *qual;
			int			n_keys;

			qual = nth(i, indxqual);
			n_keys = length(qual);
			if (n_keys > 0)
				pfree(runtimeKeyInfo[i]);
		}
		pfree(runtimeKeyInfo);
	}

	/* ----------------
	 *	clear out tuple table slots
	 * ----------------
	 */
	ExecClearTuple(scanstate->cstate.cs_ResultTupleSlot);
	ExecClearTuple(scanstate->css_ScanTupleSlot);
/*	  ExecClearTuple(scanstate->css_RawTupleSlot); */
}

/* ----------------------------------------------------------------
 *		ExecIndexMarkPos
 *
 * old comments
 *		Marks scan position by marking the current index.
 *		Returns nothing.
 * ----------------------------------------------------------------
 */
void
ExecIndexMarkPos(IndexScan *node)
{
	IndexScanState *indexstate;
	IndexScanDescPtr indexScanDescs;
	IndexScanDesc scanDesc;
	int			indexPtr;

	indexstate = node->indxstate;
	indexPtr = indexstate->iss_MarkIndexPtr = indexstate->iss_IndexPtr;
	indexScanDescs = indexstate->iss_ScanDescs;
	scanDesc = indexScanDescs[indexPtr];

#ifdef NOT_USED
	IndexScanMarkPosition(scanDesc);
#endif
	index_markpos(scanDesc);
}

/* ----------------------------------------------------------------
 *		ExecIndexRestrPos
 *
 * old comments
 *		Restores scan position by restoring the current index.
 *		Returns nothing.
 *
 *		XXX Assumes previously marked scan position belongs to current index
 * ----------------------------------------------------------------
 */
void
ExecIndexRestrPos(IndexScan *node)
{
	IndexScanState *indexstate;
	IndexScanDescPtr indexScanDescs;
	IndexScanDesc scanDesc;
	int			indexPtr;

	indexstate = node->indxstate;
	indexPtr = indexstate->iss_IndexPtr = indexstate->iss_MarkIndexPtr;
	indexScanDescs = indexstate->iss_ScanDescs;
	scanDesc = indexScanDescs[indexPtr];

#ifdef NOT_USED
	IndexScanRestorePosition(scanDesc);
#endif
	index_restrpos(scanDesc);
}

/* ----------------------------------------------------------------
 *		ExecInitIndexScan
  *
 *		Initializes the index scan's state information, creates
 *		scan keys, and opens the base and index relations.
 *
 *		Note: index scans have 2 sets of state information because
 *			  we have to keep track of the base relation and the
 *			  index relations.
 *