Re: Making Vars outer-join aware

Richard Guo <guofenglinux@gmail.com>

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: 2022-08-30T03:21:42Z

Lists: pgsql-hackers

Commits

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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

On Mon, Aug 29, 2022 at 2:30 PM Richard Guo <guofenglinux@gmail.com> wrote:

>
> On Fri, Aug 19, 2022 at 2:45 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
>> Here's a rebase up to HEAD, mainly to get the cfbot back in sync
>> as to what's the live patch.
>
>
> Noticed another different behavior from previous. When we try to reduce
> JOIN_LEFT to JOIN_ANTI, we want to know if the join's own quals are
> strict for any Var that was forced null by higher qual levels. We do
> that by checking whether local_nonnullable_vars and forced_null_vars
> overlap. However, the same Var from local_nonnullable_vars and
> forced_null_vars may be labeled with different varnullingrels. If that
> is the case, currently we would fail to tell they actually overlap.
>

I wonder why this is not noticed by regression tests. So I did some
search and it seems we do not have any test cases covering the
transformation we apply to reduce outer joins. I think maybe we should
add such cases in regression tests.

Thanks
Richard