Re: Making Vars outer-join aware

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

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

To: "Anton A. Melnikov" <aamelnikov@inbox.ru>

Cc: Justin Pryzby <pryzby@telsasoft.com>, Richard Guo <guofenglinux@gmail.com>, pgsql-hackers@lists.postgresql.org, "Finnerty, Jim" <jfinnert@amazon.com>

Date: 2023-05-04T12:22:04Z

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 →

Re-allow INDEX_VAR as rt_index in ChangeVarNodes().
- fbf80421ead5 16.0 landed
Fix thinkos in have_unsafe_outer_join_ref; reduce to Assert check.
- f50f029c497d 16.0 landed
Invent "join domains" to replace the below_outer_join hack.
- 3bef56e11650 16.0 landed
Do assorted mop-up in the planner.
- b448f1c8d83f 16.0 landed
Make Vars be outer-join-aware.
- 2489d76c4906 16.0 landed
Invent "multibitmapsets", and use them to speed up antijoin detection.
- e9e26b5e7166 16.0 landed
Add basic regression tests for semi/antijoin recognition.
- 0043aa6b8597 16.0 landed
Improve performance of adjust_appendrel_attrs_multilevel.
- 2f17b57017e5 16.0 landed
Refactor addition of PlaceHolderVars to joinrel targetlists.
- afa0ec30bfd1 16.0 landed
Use an explicit state flag to control PlaceHolderInfo creation.
- b3ff6c742f6c 16.0 landed
Make PlaceHolderInfo lookup O(1).
- 6569ca43973b 16.0 landed

"Anton A. Melnikov" <aamelnikov@inbox.ru> writes:
> The thing is that for custom scan nodes as readme says:
> "INDEX_VAR is abused to signify references to columns of a custom scan tuple type"
> But INDEX_VAR has a negative value, so it can not be used in varnullingrels bitmapset.
> And therefore this improvement seems will not work with custom scan nodes and some
> extensions that use such nodes.

Under what circumstances would you be trying to inject INDEX_VAR
into a nullingrel set?  Only outer-join relids should ever appear there.
AFAICS the change you propose would serve only to mask bugs.

			regards, tom lane