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Commit996fdb9

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Cause GROUP BY clause to adopt ordering operators from ORDER BY when
both clauses specify the same targets, rather than always using thedefault ordering operator. This allows 'GROUP BY foo ORDER BY foo DESC'to be done with only one sort step.
1 parentda78e3e commit996fdb9

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3 files changed

+43
-17
lines changed

3 files changed

+43
-17
lines changed

‎src/backend/parser/analyze.c‎

Lines changed: 10 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@
66
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
77
* Portions Copyright (c) 1994, Regents of the University of California
88
*
9-
*$Header: /cvsroot/pgsql/src/backend/parser/analyze.c,v 1.273 2003/06/06 15:04:02 tgl Exp $
9+
*$Header: /cvsroot/pgsql/src/backend/parser/analyze.c,v 1.274 2003/06/15 16:42:07 tgl Exp $
1010
*
1111
*-------------------------------------------------------------------------
1212
*/
@@ -1787,14 +1787,19 @@ transformSelectStmt(ParseState *pstate, SelectStmt *stmt)
17871787
*/
17881788
qry->havingQual=transformWhereClause(pstate,stmt->havingClause);
17891789

1790-
qry->groupClause=transformGroupClause(pstate,
1791-
stmt->groupClause,
1792-
qry->targetList);
1793-
1790+
/*
1791+
* Transform sorting/grouping stuff. Do ORDER BY first because both
1792+
* transformGroupClause and transformDistinctClause need the results.
1793+
*/
17941794
qry->sortClause=transformSortClause(pstate,
17951795
stmt->sortClause,
17961796
qry->targetList);
17971797

1798+
qry->groupClause=transformGroupClause(pstate,
1799+
stmt->groupClause,
1800+
qry->targetList,
1801+
qry->sortClause);
1802+
17981803
qry->distinctClause=transformDistinctClause(pstate,
17991804
stmt->distinctClause,
18001805
qry->targetList,

‎src/backend/parser/parse_clause.c‎

Lines changed: 31 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/parser/parse_clause.c,v 1.114 2003/06/06 15:04:02 tgl Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/parser/parse_clause.c,v 1.115 2003/06/15 16:42:07 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -1124,29 +1124,50 @@ findTargetlistEntry(ParseState *pstate, Node *node, List *tlist, int clause)
11241124
* transform a GROUP BY clause
11251125
*/
11261126
List*
1127-
transformGroupClause(ParseState*pstate,List*grouplist,List*targetlist)
1127+
transformGroupClause(ParseState*pstate,List*grouplist,
1128+
List*targetlist,List*sortClause)
11281129
{
11291130
List*glist=NIL,
11301131
*gl;
11311132

11321133
foreach(gl,grouplist)
11331134
{
11341135
TargetEntry*tle;
1136+
Oidordering_op;
1137+
GroupClause*grpcl;
11351138

11361139
tle=findTargetlistEntry(pstate,lfirst(gl),
11371140
targetlist,GROUP_CLAUSE);
11381141

11391142
/* avoid making duplicate grouplist entries */
1140-
if (!targetIsInSortList(tle,glist))
1141-
{
1142-
GroupClause*grpcl=makeNode(GroupClause);
1143-
1144-
grpcl->tleSortGroupRef=assignSortGroupRef(tle,targetlist);
1145-
1146-
grpcl->sortop=ordering_oper_opid(tle->resdom->restype);
1143+
if (targetIsInSortList(tle,glist))
1144+
continue;
11471145

1148-
glist=lappend(glist,grpcl);
1146+
/*
1147+
* If the GROUP BY clause matches the ORDER BY clause, we want to
1148+
* adopt the ordering operators from the latter rather than using
1149+
* the default ops. This allows "GROUP BY foo ORDER BY foo DESC" to
1150+
* be done with only one sort step. Note we are assuming that any
1151+
* user-supplied ordering operator will bring equal values together,
1152+
* which is all that GROUP BY needs.
1153+
*/
1154+
if (sortClause&&
1155+
((SortClause*)lfirst(sortClause))->tleSortGroupRef==
1156+
tle->resdom->ressortgroupref)
1157+
{
1158+
ordering_op= ((SortClause*)lfirst(sortClause))->sortop;
1159+
sortClause=lnext(sortClause);
11491160
}
1161+
else
1162+
{
1163+
ordering_op=ordering_oper_opid(tle->resdom->restype);
1164+
sortClause=NIL;/* disregard ORDER BY once match fails */
1165+
}
1166+
1167+
grpcl=makeNode(GroupClause);
1168+
grpcl->tleSortGroupRef=assignSortGroupRef(tle,targetlist);
1169+
grpcl->sortop=ordering_op;
1170+
glist=lappend(glist,grpcl);
11501171
}
11511172

11521173
returnglist;

‎src/include/parser/parse_clause.h‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $Id: parse_clause.h,v 1.30 2003/03/22 01:49:38 tgl Exp $
10+
* $Id: parse_clause.h,v 1.31 2003/06/15 16:42:08 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -22,7 +22,7 @@ extern int setTargetTable(ParseState *pstate, RangeVar *relation,
2222
externboolinterpretInhOption(InhOptioninhOpt);
2323
externNode*transformWhereClause(ParseState*pstate,Node*where);
2424
externList*transformGroupClause(ParseState*pstate,List*grouplist,
25-
List*targetlist);
25+
List*targetlist,List*sortClause);
2626
externList*transformSortClause(ParseState*pstate,List*orderlist,
2727
List*targetlist);
2828
externList*transformDistinctClause(ParseState*pstate,List*distinctlist,

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