From 989067bd2208398d803e784582e96811d652f574 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed, 7 Apr 2004 18:17:25 +0000
Subject: [PATCH] Extend set-operation planning to keep track of the sort
ordering induced by the set operation, so that redundant sorts at higher
levels can be avoided. This was foreseen a good while back, but not done.
Per request from Karel Zak.
---
src/backend/optimizer/plan/planner.c | 27 +++++++-----
src/backend/optimizer/prep/prepunion.c | 61 +++++++++++++++++++-------
src/include/optimizer/prep.h | 4 +-
3 files changed, 63 insertions(+), 29 deletions(-)
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index fea7e4fef13..c3cfe4be719 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.167 2004/02/13 22:26:30 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.168 2004/04/07 18:17:24 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -572,11 +572,23 @@ grouping_planner(Query *parse, double tuple_fraction)
if (parse->setOperations)
{
+ List *set_sortclauses;
+
/*
* Construct the plan for set operations. The result will not
* need any work except perhaps a top-level sort and/or LIMIT.
*/
- result_plan = plan_set_operations(parse);
+ result_plan = plan_set_operations(parse,
+ &set_sortclauses);
+
+ /*
+ * Calculate pathkeys representing the sort order (if any) of the
+ * set operation's result. We have to do this before overwriting
+ * the sort key information...
+ */
+ current_pathkeys = make_pathkeys_for_sortclauses(set_sortclauses,
+ result_plan->targetlist);
+ current_pathkeys = canonicalize_pathkeys(parse, current_pathkeys);
/*
* We should not need to call preprocess_targetlist, since we must
@@ -599,16 +611,7 @@ grouping_planner(Query *parse, double tuple_fraction)
errmsg("SELECT FOR UPDATE is not allowed with UNION/INTERSECT/EXCEPT")));
/*
- * We set current_pathkeys NIL indicating we do not know sort
- * order. This is correct when the top set operation is UNION
- * ALL, since the appended-together results are unsorted even if
- * the subplans were sorted. For other set operations we could be
- * smarter --- room for future improvement!
- */
- current_pathkeys = NIL;
-
- /*
- * Calculate pathkeys that represent ordering requirements
+ * Calculate pathkeys that represent result ordering requirements
*/
sort_pathkeys = make_pathkeys_for_sortclauses(parse->sortClause,
tlist);
diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c
index 9424fc71482..b703bf2b86e 100644
--- a/src/backend/optimizer/prep/prepunion.c
+++ b/src/backend/optimizer/prep/prepunion.c
@@ -14,7 +14,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.108 2004/01/18 00:50:02 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.109 2004/04/07 18:17:25 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -45,11 +45,12 @@ typedef struct
static Plan *recurse_set_operations(Node *setOp, Query *parse,
List *colTypes, bool junkOK,
- int flag, List *refnames_tlist);
+ int flag, List *refnames_tlist,
+ List **sortClauses);
static Plan *generate_union_plan(SetOperationStmt *op, Query *parse,
- List *refnames_tlist);
+ List *refnames_tlist, List **sortClauses);
static Plan *generate_nonunion_plan(SetOperationStmt *op, Query *parse,
- List *refnames_tlist);
+ List *refnames_tlist, List **sortClauses);
static List *recurse_union_children(Node *setOp, Query *parse,
SetOperationStmt *top_union,
List *refnames_tlist);
@@ -75,9 +76,12 @@ static List *adjust_inherited_tlist(List *tlist, Oid old_relid, Oid new_relid);
* This routine only deals with the setOperations tree of the given query.
* Any top-level ORDER BY requested in parse->sortClause will be added
* when we return to grouping_planner.
+ *
+ * *sortClauses is an output argument: it is set to a list of SortClauses
+ * representing the result ordering of the topmost set operation.
*/
Plan *
-plan_set_operations(Query *parse)
+plan_set_operations(Query *parse, List **sortClauses)
{
SetOperationStmt *topop = (SetOperationStmt *) parse->setOperations;
Node *node;
@@ -113,7 +117,8 @@ plan_set_operations(Query *parse)
*/
return recurse_set_operations((Node *) topop, parse,
topop->colTypes, true, -1,
- leftmostQuery->targetList);
+ leftmostQuery->targetList,
+ sortClauses);
}
/*
@@ -124,11 +129,13 @@ plan_set_operations(Query *parse)
* junkOK: if true, child resjunk columns may be left in the result
* flag: if >= 0, add a resjunk output column indicating value of flag
* refnames_tlist: targetlist to take column names from
+ * *sortClauses: receives list of SortClauses for result plan, if any
*/
static Plan *
recurse_set_operations(Node *setOp, Query *parse,
List *colTypes, bool junkOK,
- int flag, List *refnames_tlist)
+ int flag, List *refnames_tlist,
+ List **sortClauses)
{
if (IsA(setOp, RangeTblRef))
{
@@ -155,6 +162,13 @@ recurse_set_operations(Node *setOp, Query *parse,
NIL,
rtr->rtindex,
subplan);
+
+ /*
+ * We don't bother to determine the subquery's output ordering
+ * since it won't be reflected in the set-op result anyhow.
+ */
+ *sortClauses = NIL;
+
return plan;
}
else if (IsA(setOp, SetOperationStmt))
@@ -164,9 +178,11 @@ recurse_set_operations(Node *setOp, Query *parse,
/* UNIONs are much different from INTERSECT/EXCEPT */
if (op->op == SETOP_UNION)
- plan = generate_union_plan(op, parse, refnames_tlist);
+ plan = generate_union_plan(op, parse, refnames_tlist,
+ sortClauses);
else
- plan = generate_nonunion_plan(op, parse, refnames_tlist);
+ plan = generate_nonunion_plan(op, parse, refnames_tlist,
+ sortClauses);
/*
* If necessary, add a Result node to project the caller-requested
@@ -206,7 +222,8 @@ recurse_set_operations(Node *setOp, Query *parse,
*/
static Plan *
generate_union_plan(SetOperationStmt *op, Query *parse,
- List *refnames_tlist)
+ List *refnames_tlist,
+ List **sortClauses)
{
List *planlist;
List *tlist;
@@ -249,7 +266,11 @@ generate_union_plan(SetOperationStmt *op, Query *parse,
sortList = addAllTargetsToSortList(NULL, NIL, tlist, false);
plan = (Plan *) make_sort_from_sortclauses(parse, sortList, plan);
plan = (Plan *) make_unique(plan, sortList);
+ *sortClauses = sortList;
}
+ else
+ *sortClauses = NIL;
+
return plan;
}
@@ -258,23 +279,27 @@ generate_union_plan(SetOperationStmt *op, Query *parse,
*/
static Plan *
generate_nonunion_plan(SetOperationStmt *op, Query *parse,
- List *refnames_tlist)
+ List *refnames_tlist,
+ List **sortClauses)
{
Plan *lplan,
*rplan,
*plan;
List *tlist,
*sortList,
- *planlist;
+ *planlist,
+ *child_sortclauses;
SetOpCmd cmd;
/* Recurse on children, ensuring their outputs are marked */
lplan = recurse_set_operations(op->larg, parse,
op->colTypes, false, 0,
- refnames_tlist);
+ refnames_tlist,
+ &child_sortclauses);
rplan = recurse_set_operations(op->rarg, parse,
op->colTypes, false, 1,
- refnames_tlist);
+ refnames_tlist,
+ &child_sortclauses);
planlist = makeList2(lplan, rplan);
/*
@@ -315,6 +340,9 @@ generate_nonunion_plan(SetOperationStmt *op, Query *parse,
break;
}
plan = (Plan *) make_setop(cmd, plan, sortList, length(op->colTypes) + 1);
+
+ *sortClauses = sortList;
+
return plan;
}
@@ -329,6 +357,8 @@ recurse_union_children(Node *setOp, Query *parse,
SetOperationStmt *top_union,
List *refnames_tlist)
{
+ List *child_sortclauses;
+
if (IsA(setOp, SetOperationStmt))
{
SetOperationStmt *op = (SetOperationStmt *) setOp;
@@ -359,7 +389,8 @@ recurse_union_children(Node *setOp, Query *parse,
*/
return makeList1(recurse_set_operations(setOp, parse,
top_union->colTypes, false,
- -1, refnames_tlist));
+ -1, refnames_tlist,
+ &child_sortclauses));
}
/*
diff --git a/src/include/optimizer/prep.h b/src/include/optimizer/prep.h
index 6255c362307..7f38bb795a7 100644
--- a/src/include/optimizer/prep.h
+++ b/src/include/optimizer/prep.h
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/optimizer/prep.h,v 1.43 2003/12/28 21:57:37 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/optimizer/prep.h,v 1.44 2004/04/07 18:17:25 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -48,7 +48,7 @@ extern List *preprocess_targetlist(List *tlist, int command_type,
/*
* prototypes for prepunion.c
*/
-extern Plan *plan_set_operations(Query *parse);
+extern Plan *plan_set_operations(Query *parse, List **sortClauses);
extern List *find_all_inheritors(Oid parentrel);
--
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