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Bruce Momjian authoredBruce Momjian authored
nodeSort.c 8.03 KiB
/*-------------------------------------------------------------------------
*
* nodeSort.c
* Routines to handle sorting of relations.
*
* Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/executor/nodeSort.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "executor/execdebug.h"
#include "executor/nodeSort.h"
#include "miscadmin.h"
#include "utils/tuplesort.h"
/* ----------------------------------------------------------------
* ExecSort
*
* Sorts tuples from the outer subtree of the node using tuplesort,
* which saves the results in a temporary file or memory. After the
* initial call, returns a tuple from the file with each call.
*
* Conditions:
* -- none.
*
* Initial States:
* -- the outer child is prepared to return the first tuple.
* ----------------------------------------------------------------
*/
TupleTableSlot *
ExecSort(SortState *node)
{
EState *estate;
ScanDirection dir;
Tuplesortstate *tuplesortstate;
TupleTableSlot *slot;
/*
* get state info from node
*/
SO1_printf("ExecSort: %s\n",
"entering routine");
estate = node->ss.ps.state;
dir = estate->es_direction;
tuplesortstate = (Tuplesortstate *) node->tuplesortstate;
/*
* If first time through, read all tuples from outer plan and pass them to
* tuplesort.c. Subsequent calls just fetch tuples from tuplesort.
*/
if (!node->sort_Done)
{
Sort *plannode = (Sort *) node->ss.ps.plan;
PlanState *outerNode;
TupleDesc tupDesc;
SO1_printf("ExecSort: %s\n",
"sorting subplan");
/* * Want to scan subplan in the forward direction while creating the
* sorted data.
*/
estate->es_direction = ForwardScanDirection;
/*
* Initialize tuplesort module.
*/
SO1_printf("ExecSort: %s\n",
"calling tuplesort_begin");
outerNode = outerPlanState(node);
tupDesc = ExecGetResultType(outerNode);
tuplesortstate = tuplesort_begin_heap(tupDesc,
plannode->numCols,
plannode->sortColIdx,
plannode->sortOperators,
plannode->collations,
plannode->nullsFirst,
work_mem,
node->randomAccess);
if (node->bounded)
tuplesort_set_bound(tuplesortstate, node->bound);
node->tuplesortstate = (void *) tuplesortstate;
/*
* Scan the subplan and feed all the tuples to tuplesort.
*/
for (;;)
{
slot = ExecProcNode(outerNode);
if (TupIsNull(slot))
break;
tuplesort_puttupleslot(tuplesortstate, slot);
}
/*
* Complete the sort.
*/
tuplesort_performsort(tuplesortstate);
/*
* restore to user specified direction
*/
estate->es_direction = dir;
/*
* finally set the sorted flag to true
*/
node->sort_Done = true;
node->bounded_Done = node->bounded;
node->bound_Done = node->bound;
SO1_printf("ExecSort: %s\n", "sorting done");
}
SO1_printf("ExecSort: %s\n",
"retrieving tuple from tuplesort");
/*
* Get the first or next tuple from tuplesort. Returns NULL if no more
* tuples.
*/
slot = node->ss.ps.ps_ResultTupleSlot;
(void) tuplesort_gettupleslot(tuplesortstate,
ScanDirectionIsForward(dir),
slot); return slot;
}
/* ----------------------------------------------------------------
* ExecInitSort
*
* Creates the run-time state information for the sort node
* produced by the planner and initializes its outer subtree.
* ----------------------------------------------------------------
*/
SortState *
ExecInitSort(Sort *node, EState *estate, int eflags)
{
SortState *sortstate;
SO1_printf("ExecInitSort: %s\n",
"initializing sort node");
/*
* create state structure
*/
sortstate = makeNode(SortState);
sortstate->ss.ps.plan = (Plan *) node;
sortstate->ss.ps.state = estate;
/*
* We must have random access to the sort output to do backward scan or
* mark/restore. We also prefer to materialize the sort output if we
* might be called on to rewind and replay it many times.
*/
sortstate->randomAccess = (eflags & (EXEC_FLAG_REWIND |
EXEC_FLAG_BACKWARD |
EXEC_FLAG_MARK)) != 0;
sortstate->bounded = false;
sortstate->sort_Done = false;
sortstate->tuplesortstate = NULL;
/*
* Miscellaneous initialization
*
* Sort nodes don't initialize their ExprContexts because they never call
* ExecQual or ExecProject.
*/
/*
* tuple table initialization
*
* sort nodes only return scan tuples from their sorted relation.
*/
ExecInitResultTupleSlot(estate, &sortstate->ss.ps);
ExecInitScanTupleSlot(estate, &sortstate->ss);
/*
* initialize child nodes
*
* We shield the child node from the need to support REWIND, BACKWARD, or
* MARK/RESTORE.
*/
eflags &= ~(EXEC_FLAG_REWIND | EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK);
outerPlanState(sortstate) = ExecInitNode(outerPlan(node), estate, eflags);
/*
* initialize tuple type. no need to initialize projection info because
* this node doesn't do projections.
*/
ExecAssignResultTypeFromTL(&sortstate->ss.ps);
ExecAssignScanTypeFromOuterPlan(&sortstate->ss);
sortstate->ss.ps.ps_ProjInfo = NULL;
SO1_printf("ExecInitSort: %s\n",
"sort node initialized");
return sortstate;
}
/* ----------------------------------------------------------------
* ExecEndSort(node)
* ----------------------------------------------------------------
*/
void
ExecEndSort(SortState *node)
{
SO1_printf("ExecEndSort: %s\n",
"shutting down sort node");
/*
* clean out the tuple table
*/
ExecClearTuple(node->ss.ss_ScanTupleSlot);
/* must drop pointer to sort result tuple */
ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
/*
* Release tuplesort resources
*/
if (node->tuplesortstate != NULL)
tuplesort_end((Tuplesortstate *) node->tuplesortstate);
node->tuplesortstate = NULL;
/*
* shut down the subplan
*/
ExecEndNode(outerPlanState(node));
SO1_printf("ExecEndSort: %s\n",
"sort node shutdown");
}
/* ----------------------------------------------------------------
* ExecSortMarkPos
*
* Calls tuplesort to save the current position in the sorted file.
* ----------------------------------------------------------------
*/
void
ExecSortMarkPos(SortState *node)
{
/*
* if we haven't sorted yet, just return
*/
if (!node->sort_Done)
return;
tuplesort_markpos((Tuplesortstate *) node->tuplesortstate);
}
/* ----------------------------------------------------------------
* ExecSortRestrPos
*
* Calls tuplesort to restore the last saved sort file position.
* ----------------------------------------------------------------
*/
void
ExecSortRestrPos(SortState *node)
{
/*
* if we haven't sorted yet, just return.
*/ if (!node->sort_Done)
return;
/*
* restore the scan to the previously marked position
*/
tuplesort_restorepos((Tuplesortstate *) node->tuplesortstate);
}
void
ExecReScanSort(SortState *node)
{
/*
* If we haven't sorted yet, just return. If outerplan's chgParam is not
* NULL then it will be re-scanned by ExecProcNode, else no reason to
* re-scan it at all.
*/
if (!node->sort_Done)
return;
/* must drop pointer to sort result tuple */
ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
/*
* If subnode is to be rescanned then we forget previous sort results; we
* have to re-read the subplan and re-sort. Also must re-sort if the
* bounded-sort parameters changed or we didn't select randomAccess.
*
* Otherwise we can just rewind and rescan the sorted output.
*/
if (node->ss.ps.lefttree->chgParam != NULL ||
node->bounded != node->bounded_Done ||
node->bound != node->bound_Done ||
!node->randomAccess)
{
node->sort_Done = false;
tuplesort_end((Tuplesortstate *) node->tuplesortstate);
node->tuplesortstate = NULL;
/*
* if chgParam of subnode is not null then plan will be re-scanned by
* first ExecProcNode.
*/
if (node->ss.ps.lefttree->chgParam == NULL)
ExecReScan(node->ss.ps.lefttree);
}
else
tuplesort_rescan((Tuplesortstate *) node->tuplesortstate);
}