Horton

Re: Eager aggregation, take 3

Richard Guo <guofenglinux@gmail.com>

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From: Richard Guo <guofenglinux@gmail.com>
To: Andy Fan <zhihuifan1213@163.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>, pgsql-hackers@lists.postgresql.org
Date: 2024-03-21T10:51:55Z
Lists: pgsql-hackers

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On Tue, Mar 5, 2024 at 7:19 PM Richard Guo <guofenglinux@gmail.com> wrote:

> Here is another rebase, mainly to make the test cases more stable by
> adding ORDER BY clauses to the test queries.  Also fixed more typos in
> passing.
>

This needs another rebase after 97d85be365.  I also addressed several
issues that I identified during self-review, which include:

* In some cases GroupPathExtraData.agg_final_costs, which is the cost of
final aggregation, fails to be calculated.  This can lead to bogus cost
estimation and end up with unexpected plan.

* If the cheapest partially grouped path is generated through eager
aggregation, the number of groups estimated for the final phase will be
different from the number of groups estimated for non-split aggregation.
That is to say, we should not use 'dNumGroups' for the final aggregation
in add_paths_to_grouping_rel().

* It is possible that we may generate dummy grouped join relations, and
that would trigger the Assert in make_grouped_join_rel().

* More typo fixes.

Thanks
Richard

Commits

  1. Fix eager aggregation for semi/antijoin inner rels

  2. Cover additional errors and corner conditions in repack.c

  3. Fix volatile function evaluation in eager aggregation

  4. Fix collation handling for grouping keys in eager aggregation

  5. Rename apply_at to apply_agg_at for clarity

  6. Fix comment in eager_aggregate.sql

  7. Remove unnecessary include of "utils/fmgroids.h"

  8. Implement Eager Aggregation

  9. Allow negative aggtransspace to indicate unbounded state size

  10. Add macros for looping through a List without a ListCell.

  11. Account for the effect of lossy pages when costing bitmap scans.

  12. Fix a thinko in join_is_legal: when we decide we can implement a semijoin