[branch-54] Gate new ScalarSubqueryExec node behind session property (#22530)#22690
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rebasing this since the other PR was merged |
Related to discussion on apache#21240 and apache#21080 (comment). PR apache#21240 introduced `ScalarSubqueryExec` / `ScalarSubqueryExpr` to execute uncorrelated scalar subqueries during physical execution. The two communicate via shared in process state (a `slot` in `ExecutionProps`), which breaks distributed execution that may split execution across a network boundary between the producer (`ScalarSubqueryExec`) and the consumer expression (`ScalarSubqueryExpr`). See more details on this explanation in [datafusion-contrib/datafusion-distributed#460](datafusion-contrib/datafusion-distributed#460) Adds a new optimizer config option `datafusion.optimizer.enable_physical_uncorrelated_scalar_subquery` (default true, preserving the current behavior). When true (default), behavior is unchanged from current main; when false, all scalar subqueries are rewritten to left joins by `ScalarSubqueryToJoin` and `ScalarSubqueryExec` is never constructed (which was the previous behavior). Yes all tests pass and added `uncorrelated_scalar_subquery_rewritten_when_flag_off` to test the negative case. Yes, a new config option `datafusion.optimizer.physical_uncorrelated_scalar_subquery` (this just changes the way the query is executed but not the results)
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rebased. I added back the failing test |
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Looks good to me -- thank you @LiaCastaneda
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Which issue does this PR close?
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This PR backports #22530
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