Horton

Re: Eager aggregation, take 3

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Richard Guo <guofenglinux@gmail.com>
Cc: David Rowley <dgrowleyml@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Tender Wang <tndrwang@gmail.com>, Paul George <p.a.george19@gmail.com>, Andy Fan <zhihuifan1213@163.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>, pgsql-hackers@lists.postgresql.org, Matheus Alcantara <matheusssilv97@gmail.com>
Date: 2025-10-08T14:45:12Z
Lists: pgsql-hackers 
On Tue, Oct 7, 2025 at 6:57 AM Richard Guo <guofenglinux@gmail.com> wrote:
> > 10. I don't think this comment quite makes sense:
> >
> >  * "apply_at" tracks the lowest join level at which partial aggregation is
> >  * applied.
> >
> > maybe "minimum set of rels to join before partial aggregation can be applied"?
> I've updated the comment for apply_at to clarify that it refers to the
> relids at which partial aggregation is applied.
>
> I've also updated the comments within RelAggInfo to use one-line
> style.
>
> I retained the name of this field though.

For what it's worth, I also don't like that field name. I'm not sure
what to propose instead, but I don't think apply_at is very clear.

-- 
Robert Haas
EDB: http://www.enterprisedb.com

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