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[jira] [Created] (CALCITE-2452) RexSimplify: avoid multiple similar optimization passes over the same nodes


Vladimir Sitnikov created CALCITE-2452:
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             Summary: RexSimplify: avoid multiple similar optimization passes over the same nodes
                 Key: CALCITE-2452
                 URL: https://issues.apache.org/jira/browse/CALCITE-2452
             Project: Calcite
          Issue Type: Sub-task
            Reporter: Vladimir Sitnikov
            Assignee: Julian Hyde


simplifyAndTerms(List<RexNode> terms) has two loops and it calls simplify on each expression twice.

simplifyAnd(RexCall e) calls simplifyList (that walks all the tree down), then simplifyAnd2ForUnknownAsFalse calls simplify_ again.

It looks like just one pass should be sufficient for most of the cases, and the logic should probably be adjusted as follows:
{code:java}
simplify(RexNode node){
  // e.g. simplify the node with assumption that all the arguments were simplified, etc, avoid complicated checks
  node = simplifyTrivialCases(node); 

  // this walks over the tree, simplifies operands first then simplifies the call itself
  node = simplifyArgumentsThenSimplifyNode(node); 
  return node;
}


Method naming should clearly indicate that the method is heavy, so it would not accidentally be used.




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