Horton

Re: Making Vars outer-join aware

Richard Guo <guofenglinux@gmail.com>

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From: Richard Guo <guofenglinux@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Pg Hackers <pgsql-hackers@lists.postgresql.org>, "Finnerty, Jim" <jfinnert@amazon.com>
Date: 2022-11-10T10:13:54Z
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).

On Thu, Aug 25, 2022 at 6:27 PM Richard Guo <guofenglinux@gmail.com> wrote:

> I'm not sure if I understand it correctly. If we are given the first
> order from the parser, the SpecialJoinInfo for the B/C join would have
> min_lefthand as containing both B and the A/B join. And this
> SpecialJoinInfo would make the B/C join be invalid, which is not what we
> want.
>

Now I see how this works from v6 patch.  Once we notice identity 3
applies, we will remove the lower OJ's ojrelid from the min_lefthand or
min_righthand so that the commutation is allowed.  So in this case, the
A/B join would be removed from B/C join's min_lefthand when we build the
SpecialJoinInfo for B/C join, and that makes the B/C join to be legal.

BTW, inner_join_rels can contain base Relids and OJ Relids.  Maybe we
can revise the comments a bit for it atop deconstruct_recurse and
make_outerjoininfo.  The same for the comments of qualscope, ojscope and
outerjoin_nonnullable atop distribute_qual_to_rels.

The README mentions restriction_is_computable_at(), I think it should be
clause_is_computable_at().

Thanks
Richard