/*-------------------------------------------------------------------------
*
* nodeRecursiveunion.c
* routines to handle RecursiveUnion nodes.
*
* To implement UNION (without ALL), we need a hashtable that stores tuples
* already seen. The hash key is computed from the grouping columns.
*
*
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/executor/nodeRecursiveunion.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "executor/execdebug.h"
#include "executor/nodeRecursiveunion.h"
#include "miscadmin.h"
#include "utils/memutils.h"
/*
* Initialize the hash table to empty.
*/
static void
build_hash_table(RecursiveUnionState *rustate)
{
RecursiveUnion *node = (RecursiveUnion *) rustate->ps.plan;
TupleDesc desc = ExecGetResultType(outerPlanState(rustate));
Assert(node->numCols > 0);
Assert(node->numGroups > 0);
rustate->hashtable = BuildTupleHashTable(&rustate->ps,
desc,
node->numCols,
node->dupColIdx,
rustate->eqfuncoids,
rustate->hashfunctions,
node->numGroups,
0,
rustate->tableContext,
rustate->tempContext,
false);
}
/* ----------------------------------------------------------------
* ExecRecursiveUnion(node)
*
* Scans the recursive query sequentially and returns the next
* qualifying tuple.
*
* 1. evaluate non recursive term and assign the result to RT
*
* 2. execute recursive terms
*
* 2.1 WT := RT
* 2.2 while WT is not empty repeat 2.3 to 2.6. if WT is empty returns RT
* 2.3 replace the name of recursive term with WT
* 2.4 evaluate the recursive term and store into WT
* 2.5 append WT to RT
* 2.6 go back to 2.2
* ----------------------------------------------------------------
*/
static TupleTableSlot *
ExecRecursiveUnion(PlanState *pstate)
{
RecursiveUnionState *node = castNode(RecursiveUnionState, pstate);
PlanState *outerPlan = outerPlanState(node);
PlanState *innerPlan = innerPlanState(node);
RecursiveUnion *plan = (RecursiveUnion *) node->ps.plan;
TupleTableSlot *slot;
bool isnew;
CHECK_FOR_INTERRUPTS();
/* 1. Evaluate non-recursive term */
if (!node->recursing)
{
for (;;)
{
slot = ExecProcNode(outerPlan);
if (TupIsNull(slot))
break;
if (plan->numCols > 0)
{
/* Find or build hashtable entry for this tuple's group */
LookupTupleHashEntry(node->hashtable, slot, &isnew);
/* Must reset temp context after each hashtable lookup */
MemoryContextReset(node->tempContext);
/* Ignore tuple if already seen */
if (!isnew)
continue;
}
/* Each non-duplicate tuple goes to the working table ... */
tuplestore_puttupleslot(node->working_table, slot);
/* ... and to the caller */
return slot;
}
node->recursing = true;
}
/* 2. Execute recursive term */
for (;;)
{
slot = ExecProcNode(innerPlan);
if (TupIsNull(slot))
{
/* Done if there's nothing in the intermediate table */
if (node->intermediate_empty)
break;
/* done with old working table ... */
tuplestore_end(node->working_table);
/* intermediate table becomes working table */
node->working_table = node->intermediate_table;
/* create new empty intermediate table */
node->intermediate_table = tuplestore_begin_heap(false, false,
work_mem);
node->intermediate_empty = true;
/* reset the recursive term */
innerPlan->chgParam = bms_add_member(innerPlan->chgParam,
plan->wtParam);
/* and continue fetching from recursive term */
continue;
}
if (plan->numCols > 0)
{
/* Find or build hashtable entry for this tuple's group */
LookupTupleHashEntry(node->hashtable, slot, &isnew);
/* Must reset temp context after each hashtable lookup */
MemoryContextReset(node->tempContext);
/* Ignore tuple if already seen */
if (!isnew)
continue;
}
/* Else, tuple is good; stash it in intermediate table ... */
node->intermediate_empty = false;
tuplestore_puttupleslot(node->intermediate_table, slot);
/* ... and return it */
return slot;
}
return NULL;
}
/* ----------------------------------------------------------------
* ExecInitRecursiveUnionScan
* ----------------------------------------------------------------
*/
RecursiveUnionState *
ExecInitRecursiveUnion(RecursiveUnion *node, EState *estate, int eflags)
{
RecursiveUnionState *rustate;
ParamExecData *prmdata;
/* check for unsupported flags */
Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
/*
* create state structure
*/
rustate = makeNode(RecursiveUnionState);
rustate->ps.plan = (Plan *) node;
rustate->ps.state = estate;
rustate->ps.ExecProcNode = ExecRecursiveUnion;
rustate->eqfuncoids = NULL;
rustate->hashfunctions = NULL;
rustate->hashtable = NULL;
rustate->tempContext = NULL;
rustate->tableContext = NULL;
/* initialize processing state */
rustate->recursing = false;
rustate->intermediate_empty = true;
rustate->working_table = tuplestore_begin_heap(false, false, work_mem);
rustate->intermediate_table = tuplestore_begin_heap(false, false, work_mem);
/*
* If hashing, we need a per-tuple memory context for comparisons, and a
* longer-lived context to store the hash table. The table can't just be
* kept in the per-query context because we want to be able to throw it
* away when rescanning.
*/
if (node->numCols > 0)
{
rustate->tempContext =
AllocSetContextCreate(CurrentMemoryContext,
"RecursiveUnion",
ALLOCSET_DEFAULT_SIZES);
rustate->tableContext =
AllocSetContextCreate(CurrentMemoryContext,
"RecursiveUnion hash table",
ALLOCSET_DEFAULT_SIZES);
}
/*
* Make the state structure available to descendant WorkTableScan nodes
* via the Param slot reserved for it.
*/
prmdata = &(estate->es_param_exec_vals[node->wtParam]);
Assert(prmdata->execPlan == NULL);
prmdata->value = PointerGetDatum(rustate);
prmdata->isnull = false;
/*
* Miscellaneous initialization
*
* RecursiveUnion plans don't have expression contexts because they never
* call ExecQual or ExecProject.
*/
Assert(node->plan.qual == NIL);
/*
* RecursiveUnion nodes still have Result slots, which hold pointers to
* tuples, so we have to initialize them.
*/
ExecInitResultTypeTL(&rustate->ps);
/*
* Initialize result tuple type. (Note: we have to set up the result type
* before initializing child nodes, because nodeWorktablescan.c expects it
* to be valid.)
*/
rustate->ps.ps_ProjInfo = NULL;
/*
* initialize child nodes
*/
outerPlanState(rustate) = ExecInitNode(outerPlan(node), estate, eflags);
innerPlanState(rustate) = ExecInitNode(innerPlan(node), estate, eflags);
/*
* If hashing, precompute fmgr lookup data for inner loop, and create the
* hash table.
*/
if (node->numCols > 0)
{
execTuplesHashPrepare(node->numCols,
node->dupOperators,
&rustate->eqfuncoids,
&rustate->hashfunctions);
build_hash_table(rustate);
}
return rustate;
}
/* ----------------------------------------------------------------
* ExecEndRecursiveUnionScan
*
* frees any storage allocated through C routines.
* ----------------------------------------------------------------
*/
void
ExecEndRecursiveUnion(RecursiveUnionState *node)
{
/* Release tuplestores */
tuplestore_end(node->working_table);
tuplestore_end(node->intermediate_table);
/* free subsidiary stuff including hashtable */
if (node->tempContext)
MemoryContextDelete(node->tempContext);
if (node->tableContext)
MemoryContextDelete(node->tableContext);
/*
* close down subplans
*/
ExecEndNode(outerPlanState(node));
ExecEndNode(innerPlanState(node));
}
/* ----------------------------------------------------------------
* ExecReScanRecursiveUnion
*
* Rescans the relation.
* ----------------------------------------------------------------
*/
void
ExecReScanRecursiveUnion(RecursiveUnionState *node)
{
PlanState *outerPlan = outerPlanState(node);
PlanState *innerPlan = innerPlanState(node);
RecursiveUnion *plan = (RecursiveUnion *) node->ps.plan;
/*
* Set recursive term's chgParam to tell it that we'll modify the working
* table and therefore it has to rescan.
*/
innerPlan->chgParam = bms_add_member(innerPlan->chgParam, plan->wtParam);
/*
* if chgParam of subnode is not null then plan will be re-scanned by
* first ExecProcNode. Because of above, we only have to do this to the
* non-recursive term.
*/
if (outerPlan->chgParam == NULL)
ExecReScan(outerPlan);
/* Release any hashtable storage */
if (node->tableContext)
MemoryContextResetAndDeleteChildren(node->tableContext);
/* And rebuild empty hashtable if needed */
if (plan->numCols > 0)
build_hash_table(node);
/* reset processing state */
node->recursing = false;
node->intermediate_empty = true;
tuplestore_clear(node->working_table);
tuplestore_clear(node->intermediate_table);
}