deleteBy is broken in some cases

[functora]

Function deleteBy is broken in cases where at least one of the fields of composite unique key is nullable.

[parsonsmatt]

Hm, that's not good. Can you describe the behavior you observe?

[functora]

Here is an example:

deleteDir ::
  BotId ->
  Maybe DirId ->
  Integer ->
  ReaderT SqlBackend IO ()
deleteDir botId mParId idx =
  --
  -- NOTE : esqueleto query always works, but vanilla persistent
  -- query is not working in cases where mParId == Nothing,
  -- probably null /= null sql problems here...
  --
  -- P.deleteBy $ UniqueDir botId mParId idx
  --
  delete . from $ \dir ->
    where_
      $ ( dir ^: DirBotId ==. val botId
        )
      &&. ( dir ^: DirParentId & case mParId of
              Nothing -> isNothing
              Just parId -> (==. val (Just parId))
          )
      &&. ( dir ^: DirIdx ==. val idx
          )