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Restructure parsetree representation of DECLARE CURSOR: now it's a

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utility statement (DeclareCursorStmt) with a SELECT query dangling from
it, rather than a SELECT query with a few unusual fields in it.  Add
code to determine whether a planned query can safely be run backwards.
If DECLARE CURSOR specifies SCROLL, ensure that the plan can be run
backwards by adding a Materialize plan node if it can't.  Without SCROLL,
you get an error if you try to fetch backwards from a cursor that can't
handle it.  (There is still some discussion about what the exact
behavior should be, but this is necessary infrastructure in any case.)
Along the way, make EXPLAIN DECLARE CURSOR work.
This commit is contained in:
Tom Lane
2003-03-10 03:53:52 +00:00
parent b9e8ffcd5d
commit aa83bc04e0
40 changed files with 664 additions and 574 deletions
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28
src/backend/optimizer/plan/subselect.c
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@@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/subselect.c,v 1.72 2003/02/09 06:56:27 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/subselect.c,v 1.73 2003/03/10 03:53:50 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -222,7 +222,7 @@ make_subplan(SubLink *slink, List *lefthand, bool isTopQual)
slink->subLinkType == ANY_SUBLINK)
tuple_fraction = 0.5; /* 50% */
else
tuple_fraction = -1.0; /* default behavior */
tuple_fraction = 0.0; /* default behavior */
/*
* Generate the plan for the subquery.
@@ -336,12 +336,6 @@ make_subplan(SubLink *slink, List *lefthand, bool isTopQual)
* is anything more complicated than a plain sequential scan, and we
* do it even for seqscan if the qual appears selective enough to
* eliminate many tuples.
*
* XXX It's pretty ugly to be inserting a MATERIAL node at this
* point. Since subquery_planner has already run SS_finalize_plan
* on the subplan tree, we have to kluge up parameter lists for
* the MATERIAL node. Possibly this could be fixed by postponing
* SS_finalize_plan processing until setrefs.c is run.
*/
else if (node->parParam == NIL)
{
@@ -380,23 +374,7 @@ make_subplan(SubLink *slink, List *lefthand, bool isTopQual)
}
if (use_material)
{
Plan *matplan;
Path matpath; /* dummy for result of cost_material */
matplan = (Plan *) make_material(plan->targetlist, plan);
/* need to calculate costs */
cost_material(&matpath,
plan->total_cost,
plan->plan_rows,
plan->plan_width);
matplan->startup_cost = matpath.startup_cost;
matplan->total_cost = matpath.total_cost;
matplan->plan_rows = plan->plan_rows;
matplan->plan_width = plan->plan_width;
/* parameter kluge --- see comments above */
matplan->extParam = bms_copy(plan->extParam);
matplan->allParam = bms_copy(plan->allParam);
node->plan = plan = matplan;
node->plan = plan = materialize_finished_plan(plan);
}
}