fix: Fix performance regression for eager join_where

[nameexhaustion]

• Fixes memory-usage/performance regression on join_where in 1.19 #21145

[nameexhaustion]

During IR conversion a join_where is converted to a cross-join with subsequent filters, and we rely on collapse_joins to convert to more performant joins. However the issue is that during the optimization step, members: MemberCollector was never initialized if opt_flags contained EAGER, causing collapse_joins to be skipped despite it being enabled. This caused the performance regression as we end up materializing an entire cross-join.

The fix for the linked issue is just this 1 line - the other changes are to make it so that members is initialized as-needed rather than based on combinations of flags to help avoid making similar mistakes.

[ritchie46]

Ouch.. that's a painful one.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.91%. Comparing base (a438cc3) to head (3cec05d).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #21308      +/-   ##
==========================================
+ Coverage   79.90%   79.91%   +0.01%     
==========================================
  Files        1596     1596              
  Lines      228580   228593      +13     
  Branches     2608     2608              
==========================================
+ Hits       182644   182690      +46     
+ Misses      45340    45307      -33     
  Partials      596      596              

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