513 lines
13 KiB
C
513 lines
13 KiB
C
/*-------------------------------------------------------------------------
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*
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* nodeGroup.c
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* Routines to handle group nodes (used for queries with GROUP BY clause).
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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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* DESCRIPTION
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* The Group node is designed for handling queries with a GROUP BY clause.
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* Its outer plan must deliver tuples that are sorted in the order
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* specified by the grouping columns (ie. tuples from the same group are
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* consecutive). That way, we just have to compare adjacent tuples to
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* locate group boundaries.
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/executor/nodeGroup.c,v 1.37 2000/07/12 02:37:03 tgl Exp $
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*
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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 "catalog/pg_operator.h"
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#include "executor/executor.h"
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#include "executor/nodeGroup.h"
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#include "parser/parse_oper.h"
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#include "parser/parse_type.h"
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static TupleTableSlot *ExecGroupEveryTuple(Group *node);
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static TupleTableSlot *ExecGroupOneTuple(Group *node);
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/* ---------------------------------------
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* ExecGroup -
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*
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* There are two modes in which tuples are returned by ExecGroup. If
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* tuplePerGroup is TRUE, every tuple from the same group will be
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* returned, followed by a NULL at the end of each group. This is
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* useful for Agg node which needs to aggregate over tuples of the same
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* group. (eg. SELECT salary, count(*) FROM emp GROUP BY salary)
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*
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* If tuplePerGroup is FALSE, only one tuple per group is returned. The
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* tuple returned contains only the group columns. NULL is returned only
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* at the end when no more groups are present. This is useful when
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* the query does not involve aggregates. (eg. SELECT salary FROM emp
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* GROUP BY salary)
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* ------------------------------------------
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*/
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TupleTableSlot *
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ExecGroup(Group *node)
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{
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if (node->tuplePerGroup)
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return ExecGroupEveryTuple(node);
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else
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return ExecGroupOneTuple(node);
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}
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/*
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* ExecGroupEveryTuple -
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* return every tuple with a NULL between each group
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*/
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static TupleTableSlot *
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ExecGroupEveryTuple(Group *node)
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{
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GroupState *grpstate;
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EState *estate;
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ExprContext *econtext;
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TupleDesc tupdesc;
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HeapTuple outerTuple = NULL;
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HeapTuple firsttuple;
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TupleTableSlot *outerslot;
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ProjectionInfo *projInfo;
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TupleTableSlot *resultSlot;
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bool isDone;
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/* ---------------------
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* get state info from node
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* ---------------------
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*/
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grpstate = node->grpstate;
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if (grpstate->grp_done)
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return NULL;
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estate = node->plan.state;
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econtext = grpstate->csstate.cstate.cs_ExprContext;
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tupdesc = ExecGetScanType(&grpstate->csstate);
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/*
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* We need not call ResetExprContext here because execTuplesMatch
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* will reset the per-tuple memory context once per input tuple.
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*/
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/* if we haven't returned first tuple of a new group yet ... */
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if (grpstate->grp_useFirstTuple)
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{
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grpstate->grp_useFirstTuple = FALSE;
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/*
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* note we rely on subplan to hold ownership of the tuple for as
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* long as we need it; we don't copy it.
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*/
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ExecStoreTuple(grpstate->grp_firstTuple,
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grpstate->csstate.css_ScanTupleSlot,
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InvalidBuffer, false);
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}
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else
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{
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outerslot = ExecProcNode(outerPlan(node), (Plan *) node);
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if (TupIsNull(outerslot))
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{
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grpstate->grp_done = TRUE;
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return NULL;
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}
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outerTuple = outerslot->val;
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firsttuple = grpstate->grp_firstTuple;
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if (firsttuple == NULL)
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{
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/* this should occur on the first call only */
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grpstate->grp_firstTuple = heap_copytuple(outerTuple);
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}
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else
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{
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/*
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* Compare with first tuple and see if this tuple is of the
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* same group.
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*/
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if (!execTuplesMatch(firsttuple, outerTuple,
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tupdesc,
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node->numCols, node->grpColIdx,
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grpstate->eqfunctions,
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econtext->ecxt_per_tuple_memory))
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{
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/*
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* No; save the tuple to return it next time, and return
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* NULL
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*/
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grpstate->grp_useFirstTuple = TRUE;
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heap_freetuple(firsttuple);
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grpstate->grp_firstTuple = heap_copytuple(outerTuple);
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return NULL; /* signifies the end of the group */
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}
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}
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/*
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* note we rely on subplan to hold ownership of the tuple for as
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* long as we need it; we don't copy it.
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*/
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ExecStoreTuple(outerTuple,
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grpstate->csstate.css_ScanTupleSlot,
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InvalidBuffer, false);
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}
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/* ----------------
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* form a projection tuple, store it in the result tuple
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* slot and return it.
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* ----------------
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*/
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projInfo = grpstate->csstate.cstate.cs_ProjInfo;
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econtext->ecxt_scantuple = grpstate->csstate.css_ScanTupleSlot;
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resultSlot = ExecProject(projInfo, &isDone);
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return resultSlot;
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}
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/*
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* ExecGroupOneTuple -
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* returns one tuple per group, a NULL at the end when there are no more
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* tuples.
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*/
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static TupleTableSlot *
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ExecGroupOneTuple(Group *node)
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{
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GroupState *grpstate;
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EState *estate;
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ExprContext *econtext;
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TupleDesc tupdesc;
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HeapTuple outerTuple = NULL;
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HeapTuple firsttuple;
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TupleTableSlot *outerslot;
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ProjectionInfo *projInfo;
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TupleTableSlot *resultSlot;
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bool isDone;
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/* ---------------------
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* get state info from node
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* ---------------------
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*/
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grpstate = node->grpstate;
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if (grpstate->grp_done)
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return NULL;
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estate = node->plan.state;
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econtext = node->grpstate->csstate.cstate.cs_ExprContext;
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tupdesc = ExecGetScanType(&grpstate->csstate);
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/*
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* We need not call ResetExprContext here because execTuplesMatch
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* will reset the per-tuple memory context once per input tuple.
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*/
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firsttuple = grpstate->grp_firstTuple;
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if (firsttuple == NULL)
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{
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/* this should occur on the first call only */
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outerslot = ExecProcNode(outerPlan(node), (Plan *) node);
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if (TupIsNull(outerslot))
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{
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grpstate->grp_done = TRUE;
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return NULL;
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}
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grpstate->grp_firstTuple = firsttuple =
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heap_copytuple(outerslot->val);
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}
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/*
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* find all tuples that belong to a group
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*/
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for (;;)
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{
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outerslot = ExecProcNode(outerPlan(node), (Plan *) node);
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if (TupIsNull(outerslot))
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{
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grpstate->grp_done = TRUE;
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outerTuple = NULL;
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break;
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}
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outerTuple = outerslot->val;
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/*
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* Compare with first tuple and see if this tuple is of the same
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* group.
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*/
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if (!execTuplesMatch(firsttuple, outerTuple,
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tupdesc,
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node->numCols, node->grpColIdx,
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grpstate->eqfunctions,
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econtext->ecxt_per_tuple_memory))
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break;
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}
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/* ----------------
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* form a projection tuple, store it in the result tuple
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* slot and return it.
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* ----------------
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*/
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projInfo = grpstate->csstate.cstate.cs_ProjInfo;
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/*
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* note we rely on subplan to hold ownership of the tuple for as long
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* as we need it; we don't copy it.
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*/
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ExecStoreTuple(firsttuple,
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grpstate->csstate.css_ScanTupleSlot,
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InvalidBuffer, false);
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econtext->ecxt_scantuple = grpstate->csstate.css_ScanTupleSlot;
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resultSlot = ExecProject(projInfo, &isDone);
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/* save outerTuple if we are not done yet */
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if (!grpstate->grp_done)
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{
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heap_freetuple(firsttuple);
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grpstate->grp_firstTuple = heap_copytuple(outerTuple);
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}
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return resultSlot;
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}
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/* -----------------
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* ExecInitGroup
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*
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* Creates the run-time information for the group node produced by the
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* planner and initializes its outer subtree
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* -----------------
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*/
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bool
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ExecInitGroup(Group *node, EState *estate, Plan *parent)
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{
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GroupState *grpstate;
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Plan *outerPlan;
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/*
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* assign the node's execution state
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*/
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node->plan.state = estate;
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/*
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* create state structure
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*/
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grpstate = makeNode(GroupState);
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node->grpstate = grpstate;
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grpstate->grp_useFirstTuple = FALSE;
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grpstate->grp_done = FALSE;
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grpstate->grp_firstTuple = NULL;
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/*
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* create expression context
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*/
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ExecAssignExprContext(estate, &grpstate->csstate.cstate);
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#define GROUP_NSLOTS 2
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/*
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* tuple table initialization
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*/
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ExecInitScanTupleSlot(estate, &grpstate->csstate);
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ExecInitResultTupleSlot(estate, &grpstate->csstate.cstate);
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/*
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* initializes child nodes
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*/
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outerPlan = outerPlan(node);
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ExecInitNode(outerPlan, estate, (Plan *) node);
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/* ----------------
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* initialize tuple type.
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* ----------------
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*/
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ExecAssignScanTypeFromOuterPlan((Plan *) node, &grpstate->csstate);
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/*
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* Initialize tuple type for both result and scan. This node does no
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* projection
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*/
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ExecAssignResultTypeFromTL((Plan *) node, &grpstate->csstate.cstate);
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ExecAssignProjectionInfo((Plan *) node, &grpstate->csstate.cstate);
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/*
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* Precompute fmgr lookup data for inner loop
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*/
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grpstate->eqfunctions =
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execTuplesMatchPrepare(ExecGetScanType(&grpstate->csstate),
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node->numCols,
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node->grpColIdx);
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return TRUE;
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}
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int
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ExecCountSlotsGroup(Group *node)
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{
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return ExecCountSlotsNode(outerPlan(node)) + GROUP_NSLOTS;
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}
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/* ------------------------
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* ExecEndGroup(node)
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*
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* -----------------------
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*/
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void
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ExecEndGroup(Group *node)
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{
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GroupState *grpstate;
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Plan *outerPlan;
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grpstate = node->grpstate;
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ExecFreeProjectionInfo(&grpstate->csstate.cstate);
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ExecFreeExprContext(&grpstate->csstate.cstate);
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outerPlan = outerPlan(node);
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ExecEndNode(outerPlan, (Plan *) node);
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/* clean up tuple table */
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ExecClearTuple(grpstate->csstate.css_ScanTupleSlot);
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if (grpstate->grp_firstTuple != NULL)
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{
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heap_freetuple(grpstate->grp_firstTuple);
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grpstate->grp_firstTuple = NULL;
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}
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}
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void
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ExecReScanGroup(Group *node, ExprContext *exprCtxt, Plan *parent)
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{
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GroupState *grpstate = node->grpstate;
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grpstate->grp_useFirstTuple = FALSE;
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grpstate->grp_done = FALSE;
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if (grpstate->grp_firstTuple != NULL)
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{
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heap_freetuple(grpstate->grp_firstTuple);
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grpstate->grp_firstTuple = NULL;
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}
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if (((Plan *) node)->lefttree &&
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((Plan *) node)->lefttree->chgParam == NULL)
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ExecReScan(((Plan *) node)->lefttree, exprCtxt, (Plan *) node);
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}
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/*****************************************************************************
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* Code shared with nodeUnique.c
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*****************************************************************************/
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/*
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* execTuplesMatch
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* Return true if two tuples match in all the indicated fields.
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* This is used to detect group boundaries in nodeGroup, and to
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* decide whether two tuples are distinct or not in nodeUnique.
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*
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* tuple1, tuple2: the tuples to compare
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* tupdesc: tuple descriptor applying to both tuples
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* numCols: the number of attributes to be examined
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* matchColIdx: array of attribute column numbers
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* eqFunctions: array of fmgr lookup info for the equality functions to use
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* evalContext: short-term memory context for executing the functions
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*
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* NB: evalContext is reset each time!
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*/
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bool
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execTuplesMatch(HeapTuple tuple1,
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HeapTuple tuple2,
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TupleDesc tupdesc,
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int numCols,
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AttrNumber *matchColIdx,
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FmgrInfo *eqfunctions,
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MemoryContext evalContext)
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{
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MemoryContext oldContext;
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bool result;
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int i;
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/* Reset and switch into the temp context. */
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MemoryContextReset(evalContext);
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oldContext = MemoryContextSwitchTo(evalContext);
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/*
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* We cannot report a match without checking all the fields, but we
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* can report a non-match as soon as we find unequal fields. So,
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* start comparing at the last field (least significant sort key).
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* That's the most likely to be different...
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*/
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result = true;
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for (i = numCols; --i >= 0;)
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{
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AttrNumber att = matchColIdx[i];
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Datum attr1,
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attr2;
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bool isNull1,
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isNull2;
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attr1 = heap_getattr(tuple1,
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att,
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tupdesc,
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&isNull1);
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attr2 = heap_getattr(tuple2,
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att,
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tupdesc,
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&isNull2);
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if (isNull1 != isNull2)
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{
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result = false; /* one null and one not; they aren't equal */
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break;
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}
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if (isNull1)
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continue; /* both are null, treat as equal */
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/* Apply the type-specific equality function */
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if (! DatumGetBool(FunctionCall2(&eqfunctions[i],
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attr1, attr2)))
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{
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result = false; /* they aren't equal */
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break;
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}
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}
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MemoryContextSwitchTo(oldContext);
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return result;
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}
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/*
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* execTuplesMatchPrepare
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* Look up the equality functions needed for execTuplesMatch.
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* The result is a palloc'd array.
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*/
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FmgrInfo *
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execTuplesMatchPrepare(TupleDesc tupdesc,
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int numCols,
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AttrNumber *matchColIdx)
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{
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FmgrInfo *eqfunctions = (FmgrInfo *) palloc(numCols * sizeof(FmgrInfo));
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int i;
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for (i = 0; i < numCols; i++)
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{
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AttrNumber att = matchColIdx[i];
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Oid typid = tupdesc->attrs[att - 1]->atttypid;
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Operator eq_operator;
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Form_pg_operator pgopform;
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eq_operator = oper("=", typid, typid, true);
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if (!HeapTupleIsValid(eq_operator))
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{
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elog(ERROR, "Unable to identify an equality operator for type '%s'",
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typeidTypeName(typid));
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}
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pgopform = (Form_pg_operator) GETSTRUCT(eq_operator);
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fmgr_info(pgopform->oprcode, &eqfunctions[i]);
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}
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return eqfunctions;
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}
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