[release/6.0] Fix to #27072 - Suboptimal SQL generation for query with optional navigation, its collection navigation and lateral join #27302
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smitpatel
reviewed
Jan 28, 2022
…igation, its collection navigation and lateral join When expanding collection navigation we added a check to filter out rows for which parent value is null and only afterwards match inner and outer keys. This could happen when chaining collection navigation after optional reference. Problem was that during translation we try to convert the collection subquery to a join and if that succeeds we don't need the null check anymore - joins key comparison doesn't match nulls. However, we also remove the null check when we are not able to convert to JOIN and use APPLY instead. Fix is to save the original predicate before we try to extract the join predicate and then for APPLY case re-apply the original predicate and only use the extracted join predicate for the JOIN case. Fixes #27072
smitpatel
reviewed
Jan 28, 2022
test/EFCore.SqlServer.FunctionalTests/Query/NorthwindSelectQuerySqlServerTest.cs
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smitpatel
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Jan 28, 2022
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Fixes #27072
Description
When expanding collection navigation we added a check to filter out rows for which parent value is null and only afterwards match inner and outer keys. This could happen when chaining collection navigation after optional reference. Problem was that during translation we try to convert the collection subquery to a join and if that succeeds we don't need the null check anymore - joins key comparison doesn't match nulls. However, we also remove the null check when we are not able to convert to JOIN and use APPLY instead.
Fix is to save the original predicate before we try to extract the join predicate and then for APPLY case re-apply the original predicate and only use the extracted join predicate for the JOIN case.
Customer impact
Customers running query with affected scenarios can receive incorrect results.
How found
Customer reported on 6.0
Regression
No.
Testing
Added test for user reported scenario. Several existing tests also cover the code path (and had the generated sql changed as a result), but they didn't have specific data to manifest the data corruption.
Risk
Low risk. We are re-applying the original predicate without doing any additional processing on it. Also added quirk to revert to previous behavior.