380 lines
10 KiB
C
380 lines
10 KiB
C
/*-------------------------------------------------------------------------
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*
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* nodeSeqscan.c
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* Support routines for sequential scans of relations.
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*
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* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/executor/nodeSeqscan.c,v 1.24 2000/07/12 02:37:04 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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/*
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* INTERFACE ROUTINES
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* ExecSeqScan sequentially scans a relation.
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* ExecSeqNext retrieve next tuple in sequential order.
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* ExecInitSeqScan creates and initializes a seqscan node.
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* ExecEndSeqScan releases any storage allocated.
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* ExecSeqReScan rescans the relation
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* ExecMarkPos marks scan position
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* ExecRestrPos restores scan position
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*
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*/
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#include "postgres.h"
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#include "access/heapam.h"
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#include "executor/execdebug.h"
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#include "executor/nodeSeqscan.h"
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#include "parser/parsetree.h"
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static Oid InitScanRelation(SeqScan *node, EState *estate,
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CommonScanState *scanstate);
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static TupleTableSlot *SeqNext(SeqScan *node);
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/* ----------------------------------------------------------------
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* Scan Support
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* ----------------------------------------------------------------
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*/
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/* ----------------------------------------------------------------
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* SeqNext
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*
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* This is a workhorse for ExecSeqScan
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* ----------------------------------------------------------------
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*/
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static TupleTableSlot *
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SeqNext(SeqScan *node)
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{
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HeapTuple tuple;
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HeapScanDesc scandesc;
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CommonScanState *scanstate;
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EState *estate;
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ScanDirection direction;
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TupleTableSlot *slot;
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/* ----------------
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* get information from the estate and scan state
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* ----------------
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*/
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estate = node->plan.state;
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scanstate = node->scanstate;
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scandesc = scanstate->css_currentScanDesc;
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direction = estate->es_direction;
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slot = scanstate->css_ScanTupleSlot;
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/*
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* Check if we are evaluating PlanQual for tuple of this relation.
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* Additional checking is not good, but no other way for now. We could
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* introduce new nodes for this case and handle SeqScan --> NewNode
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* switching in Init/ReScan plan...
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*/
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if (estate->es_evTuple != NULL &&
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estate->es_evTuple[node->scanrelid - 1] != NULL)
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{
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ExecClearTuple(slot);
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if (estate->es_evTupleNull[node->scanrelid - 1])
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return slot; /* return empty slot */
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/* probably ought to use ExecStoreTuple here... */
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slot->val = estate->es_evTuple[node->scanrelid - 1];
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slot->ttc_shouldFree = false;
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/*
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* Note that unlike IndexScan, SeqScan never use keys in
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* heap_beginscan (and this is very bad) - so, here we do not
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* check are keys ok or not.
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*/
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/* Flag for the next call that no more tuples */
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estate->es_evTupleNull[node->scanrelid - 1] = true;
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return (slot);
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}
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/* ----------------
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* get the next tuple from the access methods
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* ----------------
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*/
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tuple = heap_getnext(scandesc, ScanDirectionIsBackward(direction));
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/* ----------------
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* save the tuple and the buffer returned to us by the access methods
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* in our scan tuple slot and return the slot. Note: we pass 'false'
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* because tuples returned by heap_getnext() are pointers onto
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* disk pages and were not created with palloc() and so should not
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* be pfree()'d. Note also that ExecStoreTuple will increment the
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* refcount of the buffer; the refcount will not be dropped until
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* the tuple table slot is cleared.
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* ----------------
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*/
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slot = ExecStoreTuple(tuple,/* tuple to store */
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slot, /* slot to store in */
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scandesc->rs_cbuf, /* buffer associated with
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* this tuple */
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false); /* don't pfree this pointer */
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return slot;
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}
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/* ----------------------------------------------------------------
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* ExecSeqScan(node)
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*
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* Scans the relation sequentially and returns the next qualifying
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* tuple.
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* It calls the ExecScan() routine and passes it the access method
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* which retrieve tuples sequentially.
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*
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*/
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TupleTableSlot *
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ExecSeqScan(SeqScan *node)
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{
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/* ----------------
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* use SeqNext as access method
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* ----------------
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*/
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return ExecScan(node, (ExecScanAccessMtd) SeqNext);
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}
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/* ----------------------------------------------------------------
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* InitScanRelation
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*
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* This does the initialization for scan relations and
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* subplans of scans.
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* ----------------------------------------------------------------
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*/
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static Oid
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InitScanRelation(SeqScan *node, EState *estate,
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CommonScanState *scanstate)
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{
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Index relid;
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List *rangeTable;
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RangeTblEntry *rtentry;
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Oid reloid;
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ScanDirection direction;
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Relation currentRelation;
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HeapScanDesc currentScanDesc;
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RelationInfo *resultRelationInfo;
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/* ----------------
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* get the relation object id from the relid'th entry
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* in the range table, open that relation and initialize
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* the scan state...
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* ----------------
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*/
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relid = node->scanrelid;
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rangeTable = estate->es_range_table;
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rtentry = rt_fetch(relid, rangeTable);
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reloid = rtentry->relid;
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direction = estate->es_direction;
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resultRelationInfo = estate->es_result_relation_info;
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ExecOpenScanR(reloid, /* relation */
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0, /* nkeys */
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NULL, /* scan key */
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0, /* is index */
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direction, /* scan direction */
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estate->es_snapshot,
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¤tRelation, /* return: rel desc */
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(Pointer *) ¤tScanDesc); /* return: scan desc */
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scanstate->css_currentRelation = currentRelation;
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scanstate->css_currentScanDesc = currentScanDesc;
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ExecAssignScanType(scanstate, RelationGetDescr(currentRelation));
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return reloid;
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}
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/* ----------------------------------------------------------------
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* ExecInitSeqScan
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* ----------------------------------------------------------------
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*/
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bool
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ExecInitSeqScan(SeqScan *node, EState *estate, Plan *parent)
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{
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CommonScanState *scanstate;
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Oid reloid;
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HeapScanDesc scandesc;
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/* ----------------
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* Once upon a time it was possible to have an outerPlan of a SeqScan,
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* but not any more.
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* ----------------
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*/
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Assert(outerPlan((Plan *) node) == NULL);
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Assert(innerPlan((Plan *) node) == NULL);
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/* ----------------
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* assign the node's execution state
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* ----------------
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*/
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node->plan.state = estate;
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/* ----------------
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* create new CommonScanState for node
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* ----------------
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*/
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scanstate = makeNode(CommonScanState);
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node->scanstate = scanstate;
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/* ----------------
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* Miscellaneous initialization
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*
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* + create expression context for node
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* ----------------
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*/
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ExecAssignExprContext(estate, &scanstate->cstate);
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#define SEQSCAN_NSLOTS 3
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/* ----------------
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* tuple table initialization
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* ----------------
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*/
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ExecInitResultTupleSlot(estate, &scanstate->cstate);
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ExecInitScanTupleSlot(estate, scanstate);
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/* ----------------
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* initialize scan relation
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* ----------------
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*/
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reloid = InitScanRelation(node, estate, scanstate);
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scandesc = scanstate->css_currentScanDesc;
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scanstate->cstate.cs_TupFromTlist = false;
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/* ----------------
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* initialize tuple type
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* ----------------
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*/
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ExecAssignResultTypeFromTL((Plan *) node, &scanstate->cstate);
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ExecAssignProjectionInfo((Plan *) node, &scanstate->cstate);
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return TRUE;
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}
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int
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ExecCountSlotsSeqScan(SeqScan *node)
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{
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return ExecCountSlotsNode(outerPlan(node)) +
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ExecCountSlotsNode(innerPlan(node)) +
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SEQSCAN_NSLOTS;
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}
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/* ----------------------------------------------------------------
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* ExecEndSeqScan
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*
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* frees any storage allocated through C routines.
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* ----------------------------------------------------------------
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*/
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void
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ExecEndSeqScan(SeqScan *node)
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{
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CommonScanState *scanstate;
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/* ----------------
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* get information from node
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* ----------------
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*/
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scanstate = node->scanstate;
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/* ----------------
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* Free the projection info and the scan attribute info
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*
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* Note: we don't ExecFreeResultType(scanstate)
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* because the rule manager depends on the tupType
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* returned by ExecMain(). So for now, this
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* is freed at end-transaction time. -cim 6/2/91
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* ----------------
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*/
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ExecFreeProjectionInfo(&scanstate->cstate);
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ExecFreeExprContext(&scanstate->cstate);
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/* ----------------
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* close scan relation
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* ----------------
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*/
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ExecCloseR((Plan *) node);
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/* ----------------
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* clean out the tuple table
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* ----------------
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*/
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ExecClearTuple(scanstate->cstate.cs_ResultTupleSlot);
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ExecClearTuple(scanstate->css_ScanTupleSlot);
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}
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/* ----------------------------------------------------------------
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* Join Support
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* ----------------------------------------------------------------
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*/
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/* ----------------------------------------------------------------
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* ExecSeqReScan
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*
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* Rescans the relation.
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* ----------------------------------------------------------------
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*/
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void
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ExecSeqReScan(SeqScan *node, ExprContext *exprCtxt, Plan *parent)
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{
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CommonScanState *scanstate;
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EState *estate;
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Relation rel;
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HeapScanDesc scan;
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ScanDirection direction;
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scanstate = node->scanstate;
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estate = node->plan.state;
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/* If this is re-scanning of PlanQual ... */
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if (estate->es_evTuple != NULL &&
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estate->es_evTuple[node->scanrelid - 1] != NULL)
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{
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estate->es_evTupleNull[node->scanrelid - 1] = false;
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return;
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}
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rel = scanstate->css_currentRelation;
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scan = scanstate->css_currentScanDesc;
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direction = estate->es_direction;
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scan = ExecReScanR(rel, scan, direction, 0, NULL);
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scanstate->css_currentScanDesc = scan;
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}
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/* ----------------------------------------------------------------
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* ExecSeqMarkPos(node)
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*
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* Marks scan position.
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* ----------------------------------------------------------------
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*/
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void
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ExecSeqMarkPos(SeqScan *node)
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{
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CommonScanState *scanstate;
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HeapScanDesc scan;
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scanstate = node->scanstate;
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scan = scanstate->css_currentScanDesc;
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heap_markpos(scan);
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}
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/* ----------------------------------------------------------------
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* ExecSeqRestrPos
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*
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* Restores scan position.
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* ----------------------------------------------------------------
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*/
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void
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ExecSeqRestrPos(SeqScan *node)
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{
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CommonScanState *scanstate;
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HeapScanDesc scan;
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scanstate = node->scanstate;
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scan = scanstate->css_currentScanDesc;
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heap_restrpos(scan);
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}
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