Claude Brisson created CALCITE-6788:
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Summary: LoptOptimizeJoinRule should delegate costs to
optimization planner
Key: CALCITE-6788
URL: https://issues.apache.org/jira/browse/CALCITE-6788
Project: Calcite
Issue Type: Improvement
Components: core
Affects Versions: 1.38.0
Reporter: Claude Brisson
{{LoptOptimizeJoinRule}} uses costs comparisons to recursively decide whether
to add a join at the top of the joins tree or to push it down.
When doing so, instead of directly calling {{mq.getCumulativeCost(rel)}}, it
should rely on {{call.getPlanner.getCost(rel, mq)}}, which will be used
thereafter to choose the best joins tree.
This way, it becomes possible to customize the costs computation during the
heuristic joins ordering phase by just altering the {{getCost()}} method of the
optimization planner.
Without this patch, it is only possible to alter joins costs at the final phase
of the algorithm, which defeats the goal of customizing them, including during
the to-top/push-down phase.
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