[jira] [Created] (CALCITE-4466) Do not RelTraitDef.convert if the "from" trait already satisfies the "to" trait.

["Vladimir Ozerov (Jira)" <ji...@apache.org>]

Vladimir Ozerov created CALCITE-4466:
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             Summary: Do not RelTraitDef.convert if the "from" trait already satisfies the "to" trait.
                 Key: CALCITE-4466
                 URL: https://issues.apache.org/jira/browse/CALCITE-4466
             Project: Calcite
          Issue Type: Task
          Components: core
    Affects Versions: 1.26.0
            Reporter: Vladimir Ozerov
            Assignee: Vladimir Ozerov
             Fix For: 1.27.0


Consider that we have two trait defs {{A_def}} and {{B_def}}. We have a node with the trait set {{[A_from, B_from]}} that we want to convert to a node with the traits set {{[A_to, B_to]}}. Suppose that:
* A_from.satisfies(A_to) = false
* B_from.satisfies(B_to) = true

Currently, the {{VolcanoPlanner}} will invoke {{convert}} on both {{A_trait}} and {{B_trait}}, because it skips the conversion only when two traits are *equal*. In our example, it will lead to an unnecessary call to {{B_def.convert(node, B_to)}}. This is not a big problem but it forces implementors of custom traits to double-check whether the passed node already satisfies the required trait or not.

The proposal is to replace {{fromTrait.equals(toTrait)}} with {{fromTrait.satisfies(toTrait)}}.



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