Horton

Re: Eager aggregation, take 3

Richard Guo <guofenglinux@gmail.com>

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From: Richard Guo <guofenglinux@gmail.com>
To: jian he <jian.universality@gmail.com>
Cc: Robert Haas <robertmhaas@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
Date: 2024-10-29T07:51:37Z
Lists: pgsql-hackers 
On Fri, Oct 18, 2024 at 12:44 PM jian he <jian.universality@gmail.com> wrote:
> 1. root->parse->resultRelation > 0
>     just be 100% sure we are only dealing with SELECT, or we can add
> Assert at the end of setup_eager_aggregation.

Can GROUP BY clauses be used in INSERT/UPDATE/DELETE/MERGE statements?
If not, I think there is no need to check 'resultRelation > 0', as
setup_eager_aggregation already checks for GROUP BY clauses.

> 2. join type is FULL JOIN, (i am not sure about other Semijoins and
> anti-semijoins  types).

The presence of a FULL JOIN does not preclude the use of eager
aggregation.  We still can push a partial aggregation down to a level
that is above the FULL JOIN.

> 3.  root->parse->windowClause != NIL

Why does the presence of windowClause prevent the use of eager
aggregation?

> lack doc entry in doc/src/sgml/config.sgml
> we can put after varlistentry enable_bitmapscan
> we can at least mention that
> enable_eager_aggregate, The default value is <literal>off</literal>.

Yeah, that's what I need to do.

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