[release/9.0-staging] Fix to #35239 - EF9: SaveChanges() is significantly slower in .NET9 vs. .NET8 when using .ToJson() Mapping vs. PostgreSQL Legacy POCO mapping #35360
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maumar
changed the title
…s. .NET8 when using .ToJson() Mapping vs. PostgreSQL Legacy POCO mapping
AndriySvyryd
approved these changes
Dec 20, 2024
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@AndriySvyryd update: added changes to the cosmos StringDictionaryComparer. It does support nested collections and the legacy functions can be invoked (rather than just being constructed like in relational). I added targeted fix similar to what I initially did for main. |
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Looks good. Can you add the servicing template? |
AndriySvyryd
approved these changes
Jan 2, 2025
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/azp run |
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Azure Pipelines successfully started running 1 pipeline(s). |
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Fixes #35239
Safer version of #35326
Description
EF9 introduced a change in how we construct ValueComparers for some of our types (specifically collection of scalars/references), in preparation for AOT work. The way the change was implemented may cause a severe performance regression during SaveChanges operation involving multiple entities using collections of primitives (one of our highly requested features).
Customer impact
Customers performing data manipulation operations on entities with collections of primitives may experience significant performance regressions. This may also happen when no data has been changed, but sufficiently large entity graph has been loaded into change tracker. There is no workaround for this issue, apart from changing the model to not use primitive collections (which is unacceptable for majority of customers)
How found
Multiple customer reports on EF 9
Regression
Yes, from EF8. Note: this is a perf regression only, not a functional regression.
Testing
Ad hoc performance test using BenchmarkDotNet. Functional testing already covered by existing tests.
Risk
Low. The patch fix has been limited in scope to reduce the risk. Changes should only affect models with primitive collections. Added quirks just to be sure.
Perf numbers
Over 20x regression between 8 and 9 for the tested scenario.
8.0.11
9.0
9.0.2 (with fix)