postgresql/src/backend/executor/nodeResult.c

297 lines
7.2 KiB
C

/*-------------------------------------------------------------------------
*
* nodeResult.c--
* support for constant nodes needing special code.
*
* Copyright (c) 1994, Regents of the University of California
*
*
* DESCRIPTION
*
* Example: in constant queries where no relations are scanned,
* the planner generates result nodes. Examples of such queries are:
*
* retrieve (x = 1)
* and
* append emp (name = "mike", salary = 15000)
*
* Result nodes are also used to optimise queries
* with tautological qualifications like:
*
* retrieve (emp.all) where 2 > 1
*
* In this case, the plan generated is
*
* Result (with 2 > 1 qual)
* /
* SeqScan (emp.all)
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/executor/nodeResult.c,v 1.4 1997/09/08 02:22:49 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "executor/executor.h"
#include "executor/nodeResult.h"
/* ----------------------------------------------------------------
* ExecResult(node)
*
* returns the tuples from the outer plan which satisify the
* qualification clause. Since result nodes with right
* subtrees are never planned, we ignore the right subtree
* entirely (for now).. -cim 10/7/89
*
* The qualification containing only constant clauses are
* checked first before any processing is done. It always returns
* 'nil' if the constant qualification is not satisfied.
* ----------------------------------------------------------------
*/
TupleTableSlot *
ExecResult(Result * node)
{
ResultState *resstate;
TupleTableSlot *outerTupleSlot;
TupleTableSlot *resultSlot;
Plan *outerPlan;
ExprContext *econtext;
Node *qual;
bool qualResult;
bool isDone;
ProjectionInfo *projInfo;
/* ----------------
* initialize the result node's state
* ----------------
*/
resstate = node->resstate;
/* ----------------
* get the expression context
* ----------------
*/
econtext = resstate->cstate.cs_ExprContext;
/* ----------------
* check tautological qualifications like (2 > 1)
* ----------------
*/
qual = node->resconstantqual;
if (qual != NULL)
{
qualResult = ExecQual((List *) qual, econtext);
/* ----------------
* if we failed the constant qual, then there
* is no need to continue processing because regardless of
* what happens, the constant qual will be false..
* ----------------
*/
if (qualResult == false)
return NULL;
/* ----------------
* our constant qualification succeeded so now we
* throw away the qual because we know it will always
* succeed.
* ----------------
*/
node->resconstantqual = NULL;
}
if (resstate->cstate.cs_TupFromTlist)
{
ProjectionInfo *projInfo;
projInfo = resstate->cstate.cs_ProjInfo;
resultSlot = ExecProject(projInfo, &isDone);
if (!isDone)
return resultSlot;
}
/* ----------------
* retrieve a tuple that satisfy the qual from the outer plan until
* there are no more.
*
* if rs_done is 1 then it means that we were asked to return
* a constant tuple and we alread did the last time ExecResult()
* was called, so now we are through.
* ----------------
*/
outerPlan = outerPlan(node);
while (!resstate->rs_done)
{
/* ----------------
* get next outer tuple if necessary.
* ----------------
*/
if (outerPlan != NULL)
{
outerTupleSlot = ExecProcNode(outerPlan, (Plan *) node);
if (TupIsNull(outerTupleSlot))
return NULL;
resstate->cstate.cs_OuterTupleSlot = outerTupleSlot;
}
else
{
/* ----------------
* if we don't have an outer plan, then it's probably
* the case that we are doing a retrieve or an append
* with a constant target list, so we should only return
* the constant tuple once or never if we fail the qual.
* ----------------
*/
resstate->rs_done = 1;
}
/* ----------------
* get the information to place into the expr context
* ----------------
*/
resstate = node->resstate;
outerTupleSlot = resstate->cstate.cs_OuterTupleSlot;
/* ----------------
* fill in the information in the expression context
* XXX gross hack. use outer tuple as scan tuple
* ----------------
*/
econtext->ecxt_outertuple = outerTupleSlot;
econtext->ecxt_scantuple = outerTupleSlot;
/* ----------------
* form the result tuple and pass it back using ExecProject()
* ----------------
*/
projInfo = resstate->cstate.cs_ProjInfo;
resultSlot = ExecProject(projInfo, &isDone);
resstate->cstate.cs_TupFromTlist = !isDone;
return resultSlot;
}
return NULL;
}
/* ----------------------------------------------------------------
* ExecInitResult
*
* Creates the run-time state information for the result node
* produced by the planner and initailizes outer relations
* (child nodes).
* ----------------------------------------------------------------
*/
bool
ExecInitResult(Result * node, EState * estate, Plan * parent)
{
ResultState *resstate;
/* ----------------
* assign execution state to node
* ----------------
*/
node->plan.state = estate;
/* ----------------
* create new ResultState for node
* ----------------
*/
resstate = makeNode(ResultState);
resstate->rs_done = 0;
node->resstate = resstate;
/* ----------------
* Miscellanious initialization
*
* + assign node's base_id
* + assign debugging hooks and
* + create expression context for node
* ----------------
*/
ExecAssignNodeBaseInfo(estate, &resstate->cstate, parent);
ExecAssignExprContext(estate, &resstate->cstate);
#define RESULT_NSLOTS 1
/* ----------------
* tuple table initialization
* ----------------
*/
ExecInitResultTupleSlot(estate, &resstate->cstate);
/* ----------------
* then initialize children
* ----------------
*/
ExecInitNode(outerPlan(node), estate, (Plan *) node);
/*
* we don't use inner plan
*/
Assert(innerPlan(node) == NULL);
/* ----------------
* initialize tuple type and projection info
* ----------------
*/
ExecAssignResultTypeFromTL((Plan *) node, &resstate->cstate);
ExecAssignProjectionInfo((Plan *) node, &resstate->cstate);
/* ----------------
* set "are we done yet" to false
* ----------------
*/
resstate->rs_done = 0;
return TRUE;
}
int
ExecCountSlotsResult(Result * node)
{
return ExecCountSlotsNode(outerPlan(node)) + RESULT_NSLOTS;
}
/* ----------------------------------------------------------------
* ExecEndResult
*
* fees up storage allocated through C routines
* ----------------------------------------------------------------
*/
void
ExecEndResult(Result * node)
{
ResultState *resstate;
resstate = node->resstate;
/* ----------------
* Free the projection info
*
* Note: we don't ExecFreeResultType(resstate)
* 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(&resstate->cstate);
/* ----------------
* shut down subplans
* ----------------
*/
ExecEndNode(outerPlan(node), (Plan *) node);
/* ----------------
* clean out the tuple table
* ----------------
*/
ExecClearTuple(resstate->cstate.cs_ResultTupleSlot);
}