Horton

Re: Eager aggregation, take 3

Richard Guo <guofenglinux@gmail.com>

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From: Richard Guo <guofenglinux@gmail.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: 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
Date: 2025-07-24T03:21:30Z
Lists: pgsql-hackers

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On Thu, Jun 26, 2025 at 11:01 AM Richard Guo <guofenglinux@gmail.com> wrote:
> Here is the patch based on the proposed ideas.  It includes the proof
> of correctness in the README and implements the strategy of pushing
> partial aggregation only to the lowest applicable join level where it
> is deemed useful.  This is done by introducing a "Relids apply_at"
> field to track that level and ensuring that partial aggregation is
> applied only at the recorded "apply_at" level.
>
> Additionally, this patch changes how grouped relations are stored.
> Since each grouped relation represents a partially aggregated version
> of a non-grouped relation, we now associate each grouped relation with
> the RelOptInfo of the corresponding non-grouped relation.  This
> eliminates the need for a dedicated list of all grouped relations and
> avoids list searches when retrieving a grouped relation.
>
> It also addresses other previously raised concerns, such as the
> potential memory blowout risks with large partial-aggregation values,
> and includes improvements to comments and the commit message.
>
> Another change is that this feature is now enabled by default.

This patch no longer applies; here's a rebased version.  Nothing
essential has changed.

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