yesodweb / yesodweb/persistent

repsertBy

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#852 3 comments 5 reactions 0 assignees View on GitHub

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Dominant language
Haskell
Stars
486
Forks
306
PR merge metrics
No merged PRs in 30d

Description

Would Persistent users be interested in a repsertBy function being added? This is what we have in our internal codebase:

repsertBy :: (PersistEntityBackend record ~ BaseBackend backend, PersistStoreWrite backend, MonadIO m, PersistEntity record, PersistUniqueRead backend) 
          => Unique record 
          -> record 
          -> ReaderT backend m (Key record)
repsertBy unique record = do 
  mExisting <- getBy unique
  case mExisting of 
    Just (Entity key _) -> replace key record >> return key
    Nothing             -> insert record

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reviewing the existing getBy, replace, and insert entry points in Persistent and how their backend constraints are expressed. Done means adding the proposed repsertBy behavior with compatible constraints and coverage for both the existing-record and missing-record cases.

Written by the indexing model from the issue text.

Assessment

Tech stack
haskell
Domain
database
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
38/100

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