Horton

Re: Eager aggregation, take 3

Tender Wang <tndrwang@gmail.com>

View thread View on postgr.es
From: Tender Wang <tndrwang@gmail.com>
To: Richard Guo <guofenglinux@gmail.com>
Cc: Paul George <p.a.george19@gmail.com>, Andy Fan <zhihuifan1213@163.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>, pgsql-hackers@lists.postgresql.org, Robert Haas <robertmhaas@gmail.com>
Date: 2024-09-05T01:40:18Z
Lists: pgsql-hackers 
Richard Guo <guofenglinux@gmail.com> 于2024年8月21日周三 15:11写道：

> On Fri, Aug 16, 2024 at 4:14 PM Richard Guo <guofenglinux@gmail.com>
> wrote:
> > I had a self-review of this patchset and made some refactoring,
> > especially to the function that creates the RelAggInfo structure for a
> > given relation.  While there were no major changes, the code should
> > now be simpler.
>
> I found a bug in v10 patchset: when we generate the GROUP BY clauses
> for the partial aggregation that is pushed down to a non-aggregated
> relation, we may produce a clause with a tleSortGroupRef that
> duplicates one already present in the query's groupClause, which would
> cause problems.
>
> Attached is the updated version of the patchset that fixes this bug
> and includes further code refactoring.


 I review the v11 patch set, and here are a few of my thoughts:

1.  in setup_eager_aggregation(), before calling create_agg_clause_infos(),
it does
some checks if eager aggregation is available. Can we move those checks
into a function,
for example, can_eager_agg(), like can_partial_agg() does?

2.  I found that outside of joinrel.c we all use IS_DUMMY_REL,  but in
joinrel.c, Tom always uses
is_dummy_rel(). Other commiters use IS_DUMMY_REL.

3.  The attached patch does not consider FDW when creating a path for
grouped_rel or grouped_join.
Do we need to think about FDW?

I haven't finished reviewing the patch set. I will continue to learn this
feature.

-- 
Thanks,
Tender Wang

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