[jira] [Created] (CALCITE-3917) Revive pruned node when a rule generates RelNode that is already pruned

["Haisheng Yuan (Jira)" <ji...@apache.org>]

Haisheng Yuan created CALCITE-3917:
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             Summary: Revive pruned node when a rule generates RelNode that is already pruned
                 Key: CALCITE-3917
                 URL: https://issues.apache.org/jira/browse/CALCITE-3917
             Project: Calcite
          Issue Type: Improvement
          Components: core
            Reporter: Haisheng Yuan


Manually pruning nodes in rule can be dangerous. e.g.:
Logical transformation rule X matches RelNode A and generates RelNode B. Rule X thinks B is always better than A, prunes A in the rule. But if B is already in the MEMO, matched and pruned by another rule Y before X, and rule Y generates A. At the end, we may see CannotPlanException, because there is no available RelNode in the RelSet.

In this case, we'd better revive the node that is already pruned out by planner, even this can bring additional rule apply and overhead, but better than failure to plan.



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