diff options
Diffstat (limited to 'src/backend/optimizer/plan/planner.c')
| -rw-r--r-- | src/backend/optimizer/plan/planner.c | 65 |
1 files changed, 45 insertions, 20 deletions
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c index 41bb025e286..17ad449839b 100644 --- a/src/backend/optimizer/plan/planner.c +++ b/src/backend/optimizer/plan/planner.c @@ -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; } |