[GitHub] [calcite] vlsi edited a comment on issue #1703: WIP: [CALCITE-2450] Reorder RexCall predicates to a canonical form

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vlsi edited a comment on issue #1703: WIP: [CALCITE-2450] Reorder RexCall predicates to a canonical form
URL: https://github.com/apache/calcite/pull/1703#issuecomment-569614910
 
 
   > The plan changes, with same semantic but no promotion
   
   The key improvement here is plan time performance improvement.
   There are several tests that get faster.
   For instance: org.apache.calcite.test.RelMetadataTest#testPullUpPredicatesForExprsItr
   There's an assert:
   
   ```
   assertThat(inputSet.pulledUpPredicates.size(), is(18));
   ```
   
   After the change it becomes `12`, so the test extracts less predicates, thus the planning becomes faster.
   
   
   Note: even though the plan representation change, it is "one-time" change.
   In other words, the plan would be sorted in exactly the same order, so the change would make plans **more stable** in the future.
   
   > we should keep as the same plan for same query/relational expression for different Calcite version
   
   It can't always be like that. A change to the optimizer might produce a slightly different plan.
   This PR improves performance across different tests, so it is a true performance improvement.
   
   However, I do not see the way to fully reproduce "old plan representation" because "old representation" is "a random one".
   

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