diff options
Diffstat (limited to 'src/backend/optimizer/plan/createplan.c')
| -rw-r--r-- | src/backend/optimizer/plan/createplan.c | 27 |
1 files changed, 23 insertions, 4 deletions
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c index 589bebef697..6c4c345ca8e 100644 --- a/src/backend/optimizer/plan/createplan.c +++ b/src/backend/optimizer/plan/createplan.c @@ -10,7 +10,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/plan/createplan.c,v 1.194 2005/07/15 22:02:51 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/plan/createplan.c,v 1.195 2005/07/23 21:05:46 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -40,7 +40,7 @@ static List *build_relation_tlist(RelOptInfo *rel); static bool use_physical_tlist(RelOptInfo *rel); static void disuse_physical_tlist(Plan *plan, Path *path); static Join *create_join_plan(PlannerInfo *root, JoinPath *best_path); -static Append *create_append_plan(PlannerInfo *root, AppendPath *best_path); +static Plan *create_append_plan(PlannerInfo *root, AppendPath *best_path); static Result *create_result_plan(PlannerInfo *root, ResultPath *best_path); static Material *create_material_plan(PlannerInfo *root, MaterialPath *best_path); static Plan *create_unique_plan(PlannerInfo *root, UniquePath *best_path); @@ -435,7 +435,7 @@ create_join_plan(PlannerInfo *root, JoinPath *best_path) * * Returns a Plan node. */ -static Append * +static Plan * create_append_plan(PlannerInfo *root, AppendPath *best_path) { Append *plan; @@ -443,6 +443,25 @@ create_append_plan(PlannerInfo *root, AppendPath *best_path) List *subplans = NIL; ListCell *subpaths; + /* + * It is possible for the subplans list to contain only one entry, + * or even no entries. Handle these cases specially. + * + * XXX ideally, if there's just one entry, we'd not bother to generate + * an Append node but just return the single child. At the moment this + * does not work because the varno of the child scan plan won't match + * the parent-rel Vars it'll be asked to emit. + */ + if (best_path->subpaths == NIL) + { + /* Generate a Result plan with constant-FALSE gating qual */ + return (Plan *) make_result(tlist, + (Node *) list_make1(makeBoolConst(false, + false)), + NULL); + } + + /* Normal case with multiple subpaths */ foreach(subpaths, best_path->subpaths) { Path *subpath = (Path *) lfirst(subpaths); @@ -452,7 +471,7 @@ create_append_plan(PlannerInfo *root, AppendPath *best_path) plan = make_append(subplans, false, tlist); - return plan; + return (Plan *) plan; } /* |