Add join commutativity rule for reordering fact dimension join

[siddharthteotia]

Improvement Summary

• Adds PinotJoinCommuteRule to the MSE logical planner.
• When a user writes dim JOIN fact, the rule swaps the inputs so the dim ends up on the right — fixing the build-side memory pressure that the syntactic-default planner gets wrong today

Problem

• In MSE, PinotJoinExchangeNodeInsertRule decides distribution purely syntactically, and the runtime always builds the hash table from the right input (BaseJoinOperator invariant).
• So when a user writes dim JOIN fact:
  • The runtime builds a hash table from fact_tbl — the wrong side, memory-wise. For large fact tables this can exceed max_rows_in_join and fail queries that would otherwise succeed.
  • In specific cases** (non-equi joins, user-hinted broadcast, dynamic-broadcast semi-joins): the fact table is also broadcast to every worker, multiplying network cost.

Both problems share the same root: the right side is special (build side always, broadcast side sometimes), and the user's syntactic ordering puts the wrong table there.

BEFORE (user-written)                      AFTER (rule fires)

             JOIN                                       JOIN
            /    \                                     /    \
       dim_tbl  fact_tbl                          fact_tbl  dim_tbl
       (small)   (BIG)                              (BIG)   (small)

      Build side (runtime invariant):             Build side (runtime invariant):
        fact_tbl  (large hash table)  ❌            dim_tbl  (small hash table)  ✅

      Broadcast (when planner picks it,            Broadcast (when planner picks it,
      e.g. non-equi / hinted):                     e.g. non-equi / hinted):
        fact_tbl  (network blowup)    ❌            dim_tbl  (small)              ✅

Solution

• dim INNER/LEFT/RIGHT/FULL JOIN fact — auto-commuted so dim ends up on the right.
• dim JOIN fact with /*+ join_strategy='lookup' */ — previously a runtime error (LookupJoinOperator requires dim on the right); now auto-corrected. Lookup join no longer requires users to remember table order when writing the query.
• ResourceBasedQueriesTest now propagates isDimTable=true to the planner, so dim-aware rules can be exercised end-to-end (was previously a silent gap).

Testing

• Added PinotJoinCommuteRuleTest — isolated HepPlanner, every predicate branch including idempotency and the lookup auto-correct case.
• Added Plan-shape tests in PinotJoinCommutePlanTest) — real QueryEnvironment, asserts rule fires, doesn't over-fire, and respects the off-switch.
• Runtime query correctness via ResourceBasedQueriesTest — H2-compared INNER / LEFT / RIGHT / FULL OUTER, filters
• Ran Full pinot-query-planner and ResourceBasedQueriesTest - pass with zero failures.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 87.27273% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.25%. Comparing base (2910445) to head (ba0e0a4).
⚠️ Report is 20 commits behind head on master.

Files with missing lines	Patch %	Lines
.../pinot/calcite/rel/rules/PinotJoinCommuteRule.java	90.69%	1 Missing and 3 partials ⚠️
...ava/org/apache/pinot/query/catalog/PinotTable.java	50.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #18551      +/-   ##
============================================
+ Coverage     63.75%   64.25%   +0.50%     
+ Complexity     1932     1120     -812     
============================================
  Files          3292     3312      +20     
  Lines        201470   203871    +2401     
  Branches      31316    31736     +420     
============================================
+ Hits         128442   130996    +2554     
+ Misses        62735    62358     -377     
- Partials      10293    10517     +224     

Flag	Coverage Δ
custom-integration1	?
integration	0.00% <ø> (-100.00%)	⬇️
integration1	?
integration2	0.00% <ø> (ø)
java-21	64.25% <87.27%> (+0.50%)	⬆️
temurin	64.25% <87.27%> (+0.50%)	⬆️
unittests	64.25% <87.27%> (+0.50%)	⬆️
unittests1	56.71% <87.27%> (+0.91%)	⬆️
unittests2	35.49% <20.00%> (+0.23%)	⬆️

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