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: 2025-01-09T09:27:06Z
Lists: pgsql-hackers 
On Thu, Jan 9, 2025 at 12:15 PM jian he <jian.universality@gmail.com> wrote:
> hi.
> in create_grouping_expr_infos
>
>         tce = lookup_type_cache(exprType((Node *) tle->expr),
>                                 TYPECACHE_BTREE_OPFAMILY);
>         if (!OidIsValid(tce->btree_opf) ||
>             !OidIsValid(tce->btree_opintype))
>             return;
>        ....
>         /*
>          * Get the operator in the btree's opfamily.
>          */
>         eq_op = get_opfamily_member(tce->btree_opf,
>                                     tce->btree_opintype,
>                                     tce->btree_opintype,
>                                     BTEqualStrategyNumber);
>         if (!OidIsValid(eq_op))
>             return;
>         eq_opfamilies = get_mergejoin_opfamilies(eq_op);
>         if (!eq_opfamilies)
>             return;
>         btree_opfamily = linitial_oid(eq_opfamilies);
>
>
> If eq_op is valid, then we don't need to call get_mergejoin_opfamilies?
> since get_mergejoin_opfamilies output will be the same as tce->btree_opf.
> and we already checked (tce->btree_opf) is valid.
>
> In other words, I think eq_op is valid imply
> that tce->btree_opf is the value (btree opfamily) we need.

Nice catch!  Actually, we can use tce->btree_opf directly, without
needing to check its equality operator, since we know it's a btree
opfamily and it's valid.  If it were a different opfamily (such as a
hash opfamily), we would need to look up its equality operator, and
select some btree opfamily that that operator is part of.  But in this
case, that's not necessary.

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