Horton

Re: Eager aggregation, take 3

Richard Guo <guofenglinux@gmail.com>

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From: Richard Guo <guofenglinux@gmail.com>
To: Tender Wang <tndrwang@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: 2024-09-25T06:55:00Z
Lists: pgsql-hackers 
On Thu, Sep 5, 2024 at 9:40 AM Tender Wang <tndrwang@gmail.com> wrote:
> 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?

We can do this, but I'm not sure this would be better.

> 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.

They are essentially the same: IS_DUMMY_REL() is a macro that wraps
is_dummy_rel().  I think they are interchangeable, and I don’t have a
preference for which one is better.

> 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?

We may add support for foreign relations in the future, but for now, I
think we'd better not expand the scope too much until we ensure that
everything is working correctly.

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