Filter push down

[andyfengHKU]

This PR moves filter push down logic from join order enumerator to its own optimizer.

Current we push down for 3 cases

• push down index equality predicate to scan and rewrite to index scan
• push down index equality predicate to cross product and rewrite to index nested loop join
• push down conjunctive filter before column scanning

This PR also adds heuristic filter reordering so that equality predicates are executed before non-equality predicates.

[codecov]

Codecov Report

Patch coverage: 98.47% and project coverage change: -0.07 ⚠️

Comparison is base (d69f73e) 92.80% compared to head (3bc81d9) 92.74%.

❗ Current head 3bc81d9 differs from pull request most recent head bc29c74. Consider uploading reports for the commit bc29c74 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1397      +/-   ##
==========================================
- Coverage   92.80%   92.74%   -0.07%     
==========================================
  Files         642      641       -1     
  Lines       22066    22067       +1     
==========================================
- Hits        20478    20465      -13     
- Misses       1588     1602      +14     

Impacted Files	Coverage Δ
src/include/common/types/types.h	100.00% <ø> (ø)
src/include/planner/join_order_enumerator.h	100.00% <ø> (ø)
src/include/planner/query_planner.h	100.00% <ø> (ø)
src/planner/operator/logical_unwind.cpp	100.00% <ø> (ø)
src/optimizer/filter_push_down_optimizer.cpp	98.05% <98.05%> (ø)
src/include/binder/expression/expression.h	92.59% <100.00%> (ø)
src/include/optimizer/filter_push_down_optimizer.h	100.00% <100.00%> (ø)
src/optimizer/optimizer.cpp	100.00% <100.00%> (ø)
src/planner/join_order_enumerator.cpp	98.35% <100.00%> (+0.31%)	⬆️
src/planner/query_planner.cpp	94.49% <100.00%> (+0.16%)	⬆️
... and 1 more

... and 13 files with indirect coverage changes

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