Horton

Re: Making Vars outer-join aware

Richard Guo <guofenglinux@gmail.com>

View thread
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: 2022-08-17T09:25:53Z
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 Wed, Aug 17, 2022 at 4:57 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:

> On further thought, it seems better to maintain the index array
> from the start, allowing complete replacement of the linear list
> searches.  We can add a separate bool flag to denote frozen-ness.


+1 for 0001 patch. Now we process plain Vars and PlaceHolderVars in a
more consistent way when building joinrel's tlist. And this change would
make it easier to build up phnullingrels for PHVs as we climb up the
join tree.

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.


0002 patch looks good to me. Glad we can get rid of create_new_ph flag.
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.

Thanks
Richard