Rework Order Dependence Tracking in Pipelines #7006
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lnkuiper
approved these changes
Apr 8, 2023
| bool IsOrderPreserving() const override { | ||
| return true; | ||
| OrderPreservationType SourceOrder() const override { | ||
| return OrderPreservationType::NO_ORDER; |
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PhysicalWindow does not have batch indices, but maybe it should?
Not something to fix in this PR, but it would be nice to guarantee that the result of a window is returned with the groups together, and in order, and then this can be changed to FIXED_ORDER.
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This PR reworks how order-dependence of operators are tracked in pipelines - specifically, it adds an enum
OrderPreservationTypethat tracks in which way operators emit/preserve order:The goal of this is to distinguish between operators that merely emit or maintain insertion order (e.g. table scans), and operators that emit a fixed order that must be maintained (e.g. ORDER BY, top-n). This fixes an issue found by @pdet (and also encountered in the test suite when increasing parallelism of aggregate scans) where
ORDER BYinformation was incorrectly lost whenpreserve_insertion_orderwas set to false.In addition in this PR we create separate more clear methods for order dependence depending on the stage of the operator:
SinkOrderDependent,OperatorOrderandSourceOrder.