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: 2022-08-17T20:17:36Z
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).

Richard Guo <guofenglinux@gmail.com> writes:
> BTW, the comment just above the two calls to build_joinrel_tlist says:
>  * Create a new tlist containing just the vars that need to be output from
> Here by 'vars' it means both plain Vars and PlaceHolderVars, right? If
> not we may need to adjust this comment to also include PlaceHolderVars.

I think it did intend just Vars because that's all that
build_joinrel_tlist did; but we really should have updated it when we
invented PlaceHolderVars, and even more so now that build_joinrel_tlist
adds PHVs too.  I changed the wording.

> A minor comment is that seems we can get rid of phid inside
> PlaceHolderInfo, since we do not do linear list searches any more. It's
> some duplicate to the phid inside PlaceHolderVar. Currently there are
> two places referencing PlaceHolderInfo->phid, remove_rel_from_query and
> find_placeholder_info. We can use PlaceHolderVar->phid instead in both
> the two places.

Meh, I'm not excited about that.  I don't think that the phid field
is only there to make the search loops faster; it's the basic
identity of the PlaceHolderInfo.

			regards, tom lane