rdelaage
/
postgresql
mirror of https://git.postgresql.org/git/postgresql.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Cause GROUP BY clause to adopt ordering operators from ORDER BY when 

both clauses specify the same targets, rather than always using the
default ordering operator.  This allows 'GROUP BY foo ORDER BY foo DESC'
to be done with only one sort step.
This commit is contained in:
Tom Lane 2003-06-15 16:42:08 +00:00
parent da78e3e2eb
commit 996fdb9af1
3 changed files with 43 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
src/backend/parser/analyze.c
View File

@ -6,7 +6,7 @@
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Header: /cvsroot/pgsql/src/backend/parser/analyze.c,v 1.273 2003/06/06 15:04:02 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/parser/analyze.c,v 1.274 2003/06/15 16:42:07 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -1787,14 +1787,19 @@ transformSelectStmt(ParseState *pstate, SelectStmt *stmt)
*/
qry->havingQual = transformWhereClause(pstate, stmt->havingClause);
qry->groupClause = transformGroupClause(pstate,
stmt->groupClause,
qry->targetList);
/*
* Transform sorting/grouping stuff. Do ORDER BY first because both
* transformGroupClause and transformDistinctClause need the results.
*/
qry->sortClause = transformSortClause(pstate,
stmt->sortClause,
qry->targetList);
qry->groupClause = transformGroupClause(pstate,
stmt->groupClause,
qry->targetList,
qry->sortClause);
qry->distinctClause = transformDistinctClause(pstate,
stmt->distinctClause,
qry->targetList,

41
src/backend/parser/parse_clause.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/parser/parse_clause.c,v 1.114 2003/06/06 15:04:02 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/parser/parse_clause.c,v 1.115 2003/06/15 16:42:07 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -1124,7 +1124,8 @@ findTargetlistEntry(ParseState *pstate, Node *node, List *tlist, int clause)
* transform a GROUP BY clause
*/
List *
transformGroupClause(ParseState *pstate, List *grouplist, List *targetlist)
transformGroupClause(ParseState *pstate, List *grouplist,
List *targetlist, List *sortClause)
{
List *glist = NIL,
*gl;
@ -1132,21 +1133,41 @@ transformGroupClause(ParseState *pstate, List *grouplist, List *targetlist)
foreach(gl, grouplist)
{
TargetEntry *tle;
Oid ordering_op;
GroupClause *grpcl;
tle = findTargetlistEntry(pstate, lfirst(gl),
targetlist, GROUP_CLAUSE);
/* avoid making duplicate grouplist entries */
if (!targetIsInSortList(tle, glist))
if (targetIsInSortList(tle, glist))
continue;
/*
* If the GROUP BY clause matches the ORDER BY clause, we want to
* adopt the ordering operators from the latter rather than using
* the default ops. This allows "GROUP BY foo ORDER BY foo DESC" to
* be done with only one sort step. Note we are assuming that any
* user-supplied ordering operator will bring equal values together,
* which is all that GROUP BY needs.
*/
if (sortClause &&
((SortClause *) lfirst(sortClause))->tleSortGroupRef ==
tle->resdom->ressortgroupref)
{
GroupClause *grpcl = makeNode(GroupClause);
grpcl->tleSortGroupRef = assignSortGroupRef(tle, targetlist);
grpcl->sortop = ordering_oper_opid(tle->resdom->restype);
glist = lappend(glist, grpcl);
ordering_op = ((SortClause *) lfirst(sortClause))->sortop;
sortClause = lnext(sortClause);
}
else
{
ordering_op = ordering_oper_opid(tle->resdom->restype);
sortClause = NIL; /* disregard ORDER BY once match fails */
}
grpcl = makeNode(GroupClause);
grpcl->tleSortGroupRef = assignSortGroupRef(tle, targetlist);
grpcl->sortop = ordering_op;
glist = lappend(glist, grpcl);
}
return glist;

4
src/include/parser/parse_clause.h
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: parse_clause.h,v 1.30 2003/03/22 01:49:38 tgl Exp $
* $Id: parse_clause.h,v 1.31 2003/06/15 16:42:08 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -22,7 +22,7 @@ extern int setTargetTable(ParseState *pstate, RangeVar *relation,
extern bool interpretInhOption(InhOption inhOpt);
extern Node *transformWhereClause(ParseState *pstate, Node *where);
extern List *transformGroupClause(ParseState *pstate, List *grouplist,
List *targetlist);
List *targetlist, List *sortClause);
extern List *transformSortClause(ParseState *pstate, List *orderlist,
List *targetlist);
extern List *transformDistinctClause(ParseState *pstate, List *distinctlist,