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Add existsBy#1437

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parsonsmatt merged 9 commits intoyesodweb:masterfrom
MercuryTechnologies:blx/existsby
Mar 4, 2023
Merged

Add existsBy#1437
parsonsmatt merged 9 commits intoyesodweb:masterfrom
MercuryTechnologies:blx/existsby

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@blx blx commented Nov 4, 2022 •
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This adds existsBy in PersistUniqueRead, as a more efficient version of isJust <$> getBy uniq.

The intent is to provide an (a) more convenient to type and (b) more efficient way to query existence of a row by unique key.

The SQL is a combination of the exists and getBy impls, and looks like SELECT EXISTS (SELECT 1 FROM ...constraints...).

The performance difference shouldn't be large, but conceivably on wider tables (or with heavy columns eg. JSON or binary blobs), existsBy would require less serialization (just a single response column) and may allow the query planner to do an index-only plan.

What do you think?

Before submitting your PR, check that you've:

  • Documented new APIs with Haddock markup
  • Added @since declarations to the Haddock
  • Ran stylish-haskell on any changed files.
  • Adhered to the code style (see the .editorconfig file for details)

After submitting your PR:

  • Update the Changelog.md file with a link to your PR
  • Bumped the version number if there isn't an (unreleased) on the Changelog
  • Check that CI passes (or if it fails, for reasons unrelated to your change, like CI timeouts)

blx
blx commented Nov 4, 2022
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blx
blx commented Nov 4, 2022
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persistent/Database/Persist/Sql/Orphan/PersistUnique.hs
, parseEntityValues
, parseExistsResult
, updatePersistValue
)
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@blx blx Nov 4, 2022 •
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imports diff here was just stylish-haskell, aside from adding parseExistsResult on line 27

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blx commented Nov 5, 2022

CI is failing with a bunch of

Database/MongoDB/Query.hs:1692:32: error:
Error:     Not in scope: type constructor or class ‘MonadFail’
     |
1692 | aggregateCursor :: (MonadIO m, MonadFail m) => Collection -> Pipeline -> AggregateConfig -> Action m Cursor
     |                                ^^^^^^^^^

Database/MongoDB/Query.hs:1711:18: error:
Error:     Not in scope: type constructor or class ‘MonadFail’
     |
1711 |   :: (MonadIO m, MonadFail m)
     |                  ^^^^^^^^^

which looks like it's the mongoDB third-party package which I haven't touched here.

I wonder, if I hadn't edited anything in persistent-mongoDB here, would the CI have passed with pre-existing cached artifacts, or something, and not have run into any issues here?

blx
blx commented Nov 5, 2022
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parsonsmatt
parsonsmatt requested changes Dec 3, 2022
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Let's put a default impl on the class so it's a safer for backwards compatibility

@blx blx requested a review from parsonsmatt January 11, 2023 04:30
blx
blx commented Feb 2, 2023
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persistent/ChangeLog.md
## 2.14.4.4

* [#1460] https://github.com/yesodweb/persistent/pull/1460
* [#1460](https://github.com/yesodweb/persistent/pull/1460)
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@blx blx Feb 2, 2023

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This matches the format in the rest of the changelog, where the PR number links to the link, but the URL itself is not shown. I can revert these changes if you want.

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That's great - thank you!

parsonsmatt
parsonsmatt approved these changes Mar 2, 2023
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This looks great, thank you so much!

persistent/ChangeLog.md
## 2.14.4.4

* [#1460] https://github.com/yesodweb/persistent/pull/1460
* [#1460](https://github.com/yesodweb/persistent/pull/1460)
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That's great - thank you!

@parsonsmatt parsonsmatt merged commit d35142c into yesodweb:master Mar 4, 2023
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