Push down left join to workers

[eaydingol]

DESCRIPTION: PR description that will go into the change log, up to 78 characters

WIP

Main todo items:

[ ] Add checks for outer table, i.e., make sure that the push down path is only active when necessary constraints can be generated for the outer table/entry - outer table should have distribution key - if larg of the join is not a table, either the pushdown path should be inactive or the constraints / conditions should be applied to all tables

[ ] Update tests [ ] Introduce new tests [ ] Remove excessive debug messages [ ] Add clear debug messages about the plan [ ] Only introduce constraints for left joins [ ] RestrictionEquivalenceForPartitionKeys, in some cases, this check fails in query_pushdown_planning, check early and perform recursive planning for these to avoid regression --> not a regresssion, as we do not compute the result in this case. [ ] Push down constraints are not added for the nested joins [ ] Extend to other distribution methods, only works for hash partition.

[codecov[bot]]

Codecov Report

:x: Patch coverage is 85.83691% with 33 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 88.27%. Comparing base (87a1b63) to head (db85081). :warning: Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7973      +/-   ##
==========================================
- Coverage   89.19%   88.27%   -0.93%     
==========================================
  Files         285      285              
  Lines       62005    62227     +222     
  Branches     7765     7819      +54     
==========================================
- Hits        55304    54929     -375     
- Misses       4479     4993     +514     
- Partials     2222     2305      +83     

:rocket: New features to boost your workflow:

• :snowflake: Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[colm-mchugh]

I didn't have time to check the regression tests, but I assume @colm-mchugh already reviewed them. But besides that, the implementation part looks good to me, thank you!

Just confirming, yes I ran the regression tests and made some suggestions that have been incorporated (Thanks :)

Also want to note in passing, it is apparent from EXPLAIN output whether or not this feature is in effect, in addition to DEBUG messages.