[6.0.1] Query: Update table references in pushdown after moving table references to subquery #26700
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…ces to subquery Doing so causes all table references to maintain referential integrity again, which is required in processing projections in certain scenarios Resolves #26587
maumar
approved these changes
Nov 15, 2021
ajcvickers
changed the title
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Doing so causes all table references to maintain referential integrity again, which is required in processing projections in certain scenarios
Resolves #26587
Description
Pushing down a select expression in subquery causes it to transfer table references to subquery which causes intermediate phase where the referential integrity of select expression graph is violated. Processing of projection requires the graph to be consistent. We made the graph consistent again but after processing the projection so this can cause exception if projection runs some code which requires consistent graph.
Customer impact
Customer queries involving GroupBy which has aggregate applied on it and using grouping key in aggregate, if it gets pushed down (which can happen due to Skip/Take operators, joining it with other queries or other kind of composition), then it will throw exception.
How found
Customer reported on RTM package
Regression
Yes.
Testing
Added tests for the root cause scenario and also for the customer scenario.
Risk
Low. We are doing same processing as before just little early. Also added quirk to revert to previous behavior.