Avoid window functions in MR diff preloader
What does this MR do?
This MR slightly alters the MR diff preloader query to avoid window functions. Looks like using window functions + distinct might cause too many rows to be read. This problem came up with a similar preloading attempt: #329621
- Old query: https://explain.depesz.com/s/TNPr
- New query: https://explain.depesz.com/s/LcO1
Note: there is no significant performance difference here. I want to use this preloader as an example for has_one
preloading where the association definition contains an ORDER BY
clause.
Does this MR meet the acceptance criteria?
Conformity
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📋 Does this MR need a changelog?-
I have included a changelog entry. -
I have not included a changelog entry because not user facing change.
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Documentation (if required) -
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Separation of EE specific content
Availability and Testing
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Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process. -
Tested in all supported browsers -
Informed Infrastructure department of a default or new setting change, if applicable per definition of done
Security
If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:
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Label as security and @ mention @gitlab-com/gl-security/appsec
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The MR includes necessary changes to maintain consistency between UI, API, email, or other methods -
Security reports checked/validated by a reviewer from the AppSec team
Edited by Adam Hegyi