Hi Robert,
On Fri, Feb 23, 2018 at 2:53 AM, Robert Haas <[email protected]> wrote:
> On Thu, Feb 8, 2018 at 8:05 AM, Jeevan Chalke
> <[email protected]> wrote:
> > In this attached version, I have rebased my changes over new design of
> > partially_grouped_rel. The preparatory changes of adding
> > partially_grouped_rel are in 0001.
>
> I spent today hacking in 0001; results attached. The big change from
> your version is that this now uses generate_gather_paths() to add
> Gather/Gather Merge nodes (except in the case where we sort by group
> pathkeys and then Gather Merge) rather than keeping all of the bespoke
> code. That turned up to be a bit less elegant than I would have liked
> -- I had to an override_rows argument to generate_gather_paths to make
> it work. But overall I think this is still a big improvement, since
> it lets us share code instead of duplicating it. Also, it potentially
> lets us add partially-aggregated but non-parallel paths into
> partially_grouped_rel->pathlist and that should Just Work; they will
> get the Finalize Aggregate step but not the Gather. With your
> arrangement that wouldn't work.
>
> Please review/test.
>
I have reviewed and tested the patch and here are my couple of points:
/*
- * If the input rel belongs to a single FDW, so does the grouped rel.
+ * If the input rel belongs to a single FDW, so does the grouped rel.
Same
+ * for the partially_grouped_rel.
*/
grouped_rel->serverid = input_rel->serverid;
grouped_rel->userid = input_rel->userid;
grouped_rel->useridiscurrent = input_rel->useridiscurrent;
grouped_rel->fdwroutine = input_rel->fdwroutine;
+ partially_grouped_rel->serverid = input_rel->serverid;
+ partially_grouped_rel->userid = input_rel->userid;
+ partially_grouped_rel->useridiscurrent = input_rel->useridiscurrent;
+ partially_grouped_rel->fdwroutine = input_rel->fdwroutine;
In my earlier mail where I have posted a patch for this partially grouped
rel changes, I forgot to put my question on this.
I was unclear about above changes and thus passed grouped_rel whenever we
wanted to work on partially_grouped_rel to fetch relevant details.
One idea I thought about is to memcpy the struct once we have set all
required fields for grouped_rel so that we don't have to do similar stuff
for partially_grouped_rel.
---
+ * Insert a Sort node, if required. But there's no point in
+ * sorting anything but the cheapest path.
*/
- if (root->group_pathkeys)
+ if (!pathkeys_contained_in(root->group_pathkeys,
path->pathkeys))
+ {
+ if (path != linitial(partially_grouped_rel->pathlist))
+ continue;
Paths in pathlist are added by add_path(). Though we have paths is pathlist
is sorted with the cheapest total path, we generally use
RelOptInfo->cheapest_total_path instead of using first entry, unlike
partial paths. But here you use the first entry like partial paths case.
Will it better to use cheapest total path from partially_grouped_rel? This
will require calling set_cheapest on partially_grouped_rel before we call
this function.
Attached top-up patch doing this along with few indentation fixes.
Rest of the changes look good to me.
Once this gets in, I will re-base my other patches accordingly.
And, thanks for committing 0006.
Thanks
>
> --
> Robert Haas
> EnterpriseDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
>
--
Jeevan Chalke
Technical Architect, Product Development
EnterpriseDB Corporation
The Enterprise PostgreSQL Company
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 1c792a0..f6b0208 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -2453,7 +2453,8 @@ set_worktable_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
* we must do something.)
*/
void
-generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
+generate_gather_paths(PlannerInfo *root, RelOptInfo *rel,
+ bool override_rows)
{
Path *cheapest_partial_path;
Path *simple_gather_path;
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index e4f9bd4..e8f6cc5 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -6101,7 +6101,7 @@ add_paths_to_grouping_rel(PlannerInfo *root, RelOptInfo *input_rel,
*/
if (!pathkeys_contained_in(root->group_pathkeys, path->pathkeys))
{
- if (path != linitial(partially_grouped_rel->pathlist))
+ if (path != partially_grouped_rel->cheapest_total_path)
continue;
path = (Path *) create_sort_path(root,
grouped_rel,
@@ -6186,9 +6186,7 @@ add_paths_to_grouping_rel(PlannerInfo *root, RelOptInfo *input_rel,
*/
if (partially_grouped_rel->pathlist)
{
- Path *path;
-
- path = (Path *) linitial(partially_grouped_rel->pathlist);
+ Path *path = partially_grouped_rel->cheapest_total_path;
hashaggtablesize = estimate_hashagg_tablesize(path,
agg_final_costs,
@@ -6369,6 +6367,9 @@ add_paths_to_partial_grouping_rel(PlannerInfo *root,
add_path(partially_grouped_rel, path);
}
+
+ /* Now choose the best path(s) */
+ set_cheapest(partially_grouped_rel);
}
/*
diff --git a/src/include/optimizer/paths.h b/src/include/optimizer/paths.h
index 2011f66..94f9bb2 100644
--- a/src/include/optimizer/paths.h
+++ b/src/include/optimizer/paths.h
@@ -54,7 +54,7 @@ extern RelOptInfo *standard_join_search(PlannerInfo *root, int levels_needed,
List *initial_rels);
extern void generate_gather_paths(PlannerInfo *root, RelOptInfo *rel,
- bool override_rows);
+ bool override_rows);
extern int compute_parallel_worker(RelOptInfo *rel, double heap_pages,
double index_pages, int max_workers);
extern void create_partial_bitmap_paths(PlannerInfo *root, RelOptInfo *rel,
