Horton

Re: Making Vars outer-join aware

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Richard Guo <guofenglinux@gmail.com>
Cc: Pg Hackers <pgsql-hackers@lists.postgresql.org>, "Finnerty, Jim" <jfinnert@amazon.com>
Date: 2022-12-23T18:20:40Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Re-allow INDEX_VAR as rt_index in ChangeVarNodes().

  2. Fix thinkos in have_unsafe_outer_join_ref; reduce to Assert check.

  3. Invent "join domains" to replace the below_outer_join hack.

  4. Do assorted mop-up in the planner.

  5. Make Vars be outer-join-aware.

  6. Invent "multibitmapsets", and use them to speed up antijoin detection.

  7. Add basic regression tests for semi/antijoin recognition.

  8. Improve performance of adjust_appendrel_attrs_multilevel.

  9. Refactor addition of PlaceHolderVars to joinrel targetlists.

  10. Use an explicit state flag to control PlaceHolderInfo creation.

  11. Make PlaceHolderInfo lookup O(1).

Attachments

Here's a new edition of this patch series.

I shoved some preliminary refactoring into the 0001 patch,
notably splitting deconstruct_jointree into two passes.
0002-0009 cover the same ground as they did before, though
with some differences in detail.  0010-0012 are new work
mostly aimed at removing kluges we no longer need.

There are two big areas that I would still like to improve, but
I think we've run out of time to address them in the v16 cycle:

* It'd be nice to apply the regular EquivalenceClass deduction
mechanisms to outer-join equalities, instead of the
reconsider_outer_join_clauses kluge.  I've made several stabs at that
without much success.  I think that the "join domain" framework added
in 0012 is likely to provide a workable foundation, but some more
effort is needed.

* I really want to get rid of RestrictInfo.is_pushed_down and
RINFO_IS_PUSHED_DOWN(), because those seem exceedingly awkward
and squishy.  I've not gotten far with finding a better
replacement there, either.

Despite the work being unfinished, I feel that this has moved us a
long way towards outer-join handling being less of a jury-rigged
affair.

			regards, tom lane