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Add a new upper planner relation for partially-aggregated results.

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Up until now, we've abused grouped_rel->partial_pathlist as a place to
store partial paths that have been partially aggregate, but that's
really not correct, because a partial path for a relation is supposed
to be one which produces the correct results with the addition of only
a Gather or Gather Merge node, and these paths also require a Finalize
Aggregate step.  Instead, add a new partially_group_rel which can hold
either partial paths (which need to be gathered and then have
aggregation finalized) or non-partial paths (which only need to have
aggregation finalized).  This allows us to reuse generate_gather_paths
for partially_grouped_rel instead of writing new code, so that this
patch actually basically no net new code while making things cleaner,
simplifying things for pending patches for partition-wise aggregate.

Robert Haas and Jeevan Chalke.  The larger patch series of which this
patch is a part was also reviewed and tested by Antonin Houska,
Rajkumar Raghuwanshi, David Rowley, Dilip Kumar, Konstantin Knizhnik,
Pascal Legrand, Rafia Sabih, and me.

Discussion: http://postgr.es/m/CA+TgmobrzFYS3+U8a_BCy3-hOvh5UyJbC18rEcYehxhpw5=ETA@mail.gmail.com
Discussion: http://postgr.es/m/CA+TgmoZyQEjdBNuoG9-wC5GQ5GrO4544Myo13dVptvx+uLg9uQ@mail.gmail.com
This commit is contained in:
Robert Haas
2018-02-26 09:30:12 -05:00
parent 5b570d771b
commit 3bf05e096b
6 changed files with 154 additions and 153 deletions
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2
src/backend/optimizer/geqo/geqo_eval.c
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@@ -268,7 +268,7 @@ merge_clump(PlannerInfo *root, List *clumps, Clump *new_clump, bool force)
generate_partitionwise_join_paths(root, joinrel);
/* Create GatherPaths for any useful partial paths for rel */
generate_gather_paths(root, joinrel);
generate_gather_paths(root, joinrel, false);
/* Find and save the cheapest paths for this joinrel */
set_cheapest(joinrel);