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> > Prevent sorting if result is already sorted

Browse Source 
> >
> > was implemented by Jan Wieck.
> > His work is for ascending order cases.
> >
> > Here is a patch to prevent sorting also in descending
> > order cases.
> > Because I had already changed _bt_first() to position
> > backward correctly before v6.5,this patch would work.
> >
Hiroshi Inoue
Inoue@tpf.co.jp
This commit is contained in:
Bruce Momjian
1999-08-09 06:20:27 +00:00
parent 5efe31214a
commit 158fd5f1c4
9 changed files with 78 additions and 28 deletions
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65
src/backend/optimizer/plan/planner.c
View File

@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.61 1999/07/17 20:17:15 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.62 1999/08/09 06:20:26 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@ -39,7 +39,7 @@ static List *make_subplanTargetList(Query *parse, List *tlist,
static Plan *make_groupplan(List *group_tlist, bool tuplePerGroup,
List *groupClause, AttrNumber *grpColIdx,
Plan *subplan);
static bool need_sortplan(List *sortcls, Plan *plan);
static ScanDirection get_dir_to_omit_sortplan(List *sortcls, Plan *plan);
static Plan *make_sortplan(List *tlist, List *sortcls, Plan *plannode);
/*****************************************************************************
@ -303,8 +303,17 @@ union_planner(Query *parse)
}
else
{
if (parse->sortClause && need_sortplan(parse->sortClause, result_plan))
return (make_sortplan(tlist, parse->sortClause, result_plan));
if (parse->sortClause)
{
ScanDirection dir = get_dir_to_omit_sortplan(parse->sortClause, result_plan);
if (ScanDirectionIsNoMovement(dir))
return (make_sortplan(tlist, parse->sortClause, result_plan));
else
{
((IndexScan *)result_plan)->indxorderdir = dir;
return ((Plan *) result_plan);
}
}
else
return ((Plan *) result_plan);
}
@ -822,7 +831,7 @@ pg_checkretval(Oid rettype, List *queryTreeList)
/* ----------
* Support function for need_sortplan
* Support function for get scan direction to omit sortplan
* ----------
*/
static TargetEntry *
@ -845,11 +854,13 @@ get_matching_tle(Plan *plan, Resdom *resdom)
* Check if a user requested ORDER BY is already satisfied by
* the choosen index scan.
*
* Returns TRUE if sort is required, FALSE if can be omitted.
* Returns the direction of Index scan to omit sort,
* if sort is required returns NoMovementScanDirection
*
* ----------
*/
static bool
need_sortplan(List *sortcls, Plan *plan)
static ScanDirection
get_dir_to_omit_sortplan(List *sortcls, Plan *plan)
{
Relation indexRel;
IndexScan *indexScan;
@ -858,13 +869,15 @@ need_sortplan(List *sortcls, Plan *plan)
HeapTuple htup;
Form_pg_index index_tup;
int key_no = 0;
ScanDirection dir, nodir = NoMovementScanDirection;
dir = nodir;
/* ----------
* Must be an IndexScan
* ----------
*/
if (nodeTag(plan) != T_IndexScan)
return TRUE;
return nodir;
indexScan = (IndexScan *) plan;
@ -873,16 +886,16 @@ need_sortplan(List *sortcls, Plan *plan)
* ----------
*/
if (plan->lefttree != NULL)
return TRUE;
return nodir;
if (plan->righttree != NULL)
return TRUE;
return nodir;
/* ----------
* Must be a single index scan
* ----------
*/
if (length(indexScan->indxid) != 1)
return TRUE;
return nodir;
/* ----------
* Indices can only have up to 8 attributes. So an ORDER BY using
@ -890,7 +903,7 @@ need_sortplan(List *sortcls, Plan *plan)
* ----------
*/
if (length(sortcls) > 8)
return TRUE;
return nodir;
/* ----------
* The choosen Index must be a btree
@ -902,7 +915,7 @@ need_sortplan(List *sortcls, Plan *plan)
if (strcmp(nameout(&(indexRel->rd_am->amname)), "btree") != 0)
{
heap_close(indexRel);
return TRUE;
return nodir;
}
heap_close(indexRel);
@ -937,7 +950,7 @@ need_sortplan(List *sortcls, Plan *plan)
* Could this happen?
* ----------
*/
return TRUE;
return nodir;
}
if (nodeTag(tle->expr) != T_Var)
{
@ -946,7 +959,7 @@ need_sortplan(List *sortcls, Plan *plan)
* cannot be the indexed attribute
* ----------
*/
return TRUE;
return nodir;
}
var = (Var *) (tle->expr);
@ -957,7 +970,7 @@ need_sortplan(List *sortcls, Plan *plan)
* that of the index
* ----------
*/
return TRUE;
return nodir;
}
if (var->varattno != index_tup->indkey[key_no])
@ -966,7 +979,7 @@ need_sortplan(List *sortcls, Plan *plan)
* It isn't the indexed attribute.
* ----------
*/
return TRUE;
return nodir;
}
if (oprid(oper("<", resdom->restype, resdom->restype, FALSE)) != sortcl->opoid)
@ -975,7 +988,19 @@ need_sortplan(List *sortcls, Plan *plan)
* Sort order isn't in ascending order.
* ----------
*/
return TRUE;
if (ScanDirectionIsForward(dir))
return nodir;
dir = BackwardScanDirection;
}
else
{
/* ----------
* Sort order is in ascending order.
* ----------
*/
if (ScanDirectionIsBackward(dir))
return nodir;
dir = ForwardScanDirection;
}
key_no++;
@ -985,5 +1010,5 @@ need_sortplan(List *sortcls, Plan *plan)
* Index matches ORDER BY - sort not required
* ----------
*/
return FALSE;
return dir;
}