Horton

Re: Eager aggregation, take 3

Richard Guo <guofenglinux@gmail.com>

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From: Richard Guo <guofenglinux@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>, David Rowley <dgrowleyml@gmail.com>, 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: 2025-10-09T03:10:31Z
Lists: pgsql-hackers 
On Thu, Oct 9, 2025 at 11:13 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Richard Guo <guofenglinux@gmail.com> writes:
> > On Wed, Oct 8, 2025 at 11:45 PM Robert Haas <robertmhaas@gmail.com> wrote:
> >> 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.

> > This field represents the set of relids at which partial aggregation
> > is applied.  So how about naming it partial_agg_designated_relids?
> > That feels a bit verbose, though.  How about partial_agg_relids or,
> > for brevity, agg_relids instead?

> I might be missing a subtlety here, but how about
> "apply_aggregation_at" or "apply_partial_agg_at"?
>
> I don't think including "relids" in the field name adds anything,
> given the field's declared type and comments.

Fair point.

'agg' seems better to me than 'aggregation' when used in a name: it's
shorter, and it's unlikely anyone would interpret it as anything other
than "aggregation".

I kind of wonder whether we need to include 'partial' in the name.
Given the context, it seems very clear that we're referring to
partial aggregation rather than final aggregation.

So I'm weighing between "apply_partial_agg_at" and "apply_agg_at".

- 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