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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2013-08-05 15:00:57 -0400 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2013-08-05 15:01:09 -0400 |
| commit | 3ced8837db2cd602422bb36102cec73289691d40 (patch) | |
| tree | 0fae9ca9ba7f5f259ef678d685717a70710ac0c4 /src/include/optimizer/pathnode.h | |
| parent | 841c29c8b3be98ee30486ee245ebee782d4dedd4 (diff) | |
Simplify query_planner's API by having it return the top-level RelOptInfo.
Formerly, query_planner returned one or possibly two Paths for the topmost
join relation, so that grouping_planner didn't see the join RelOptInfo
(at least not directly; it didn't have any hesitation about examining
cheapest_path->parent, though). However, correct selection of the Paths
involved a significant amount of coupling between query_planner and
grouping_planner, a problem which has gotten worse over time. It seems
best to give up on this API choice and instead return the topmost
RelOptInfo explicitly. Then grouping_planner can pull out the Paths it
wants from the rel's path list. In this way we can remove all knowledge
of grouping behaviors from query_planner.
The only real benefit of the old way is that in the case of an empty
FROM clause, we never made any RelOptInfos at all, just a Path. Now
we have to gin up a dummy RelOptInfo to represent the empty FROM clause.
That's not a very big deal though.
While at it, simplify query_planner's API a bit more by having the caller
set up root->tuple_fraction and root->limit_tuples, rather than passing
those values as separate parameters. Since query_planner no longer does
anything with either value, requiring it to fill the PlannerInfo fields
seemed pretty arbitrary.
This patch just rearranges code; it doesn't (intentionally) change any
behaviors. Followup patches will do more interesting things.
Diffstat (limited to 'src/include/optimizer/pathnode.h')
| -rw-r--r-- | src/include/optimizer/pathnode.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h index bc687895bfa..9686229134e 100644 --- a/src/include/optimizer/pathnode.h +++ b/src/include/optimizer/pathnode.h @@ -142,6 +142,7 @@ extern RelOptInfo *build_join_rel(PlannerInfo *root, RelOptInfo *inner_rel, SpecialJoinInfo *sjinfo, List **restrictlist_ptr); +extern RelOptInfo *build_empty_join_rel(PlannerInfo *root); extern AppendRelInfo *find_childrel_appendrelinfo(PlannerInfo *root, RelOptInfo *rel); extern ParamPathInfo *get_baserel_parampathinfo(PlannerInfo *root, |