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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