Hoogle Search

Within LTS Haskell 24.40 (ghc-9.10.3)

Note that Stackage only displays results for the latest LTS and Nightly snapshot. Learn more.

Exact lookup

1. class PersistField a => PersistFieldSql a

   esqueleto	Database.Esqueleto.Legacy

   Tells Persistent what database column type should be used to store a Haskell type.

   Examples

   Simple Boolean Alternative

   data Switch = On | Off
   deriving (Show, Eq)
   
   instance PersistField Switch where
   toPersistValue s = case s of
   On -> PersistBool True
   Off -> PersistBool False
   fromPersistValue (PersistBool b) = if b then Right On else Right Off
   fromPersistValue x = Left $ "File.hs: When trying to deserialize a Switch: expected PersistBool, received: " <> T.pack (show x)
   
   instance PersistFieldSql Switch where
   sqlType _ = SqlBool
   

   Non-Standard Database Types

   If your database supports non-standard types, such as Postgres' uuid, you can use SqlOther to use them:

   import qualified Data.UUID as UUID
   instance PersistField UUID where
   toPersistValue = PersistLiteralEncoded . toASCIIBytes
   fromPersistValue (PersistLiteralEncoded uuid) =
   case fromASCIIBytes uuid of
   Nothing -> Left $ "Model/CustomTypes.hs: Failed to deserialize a UUID; received: " <> T.pack (show uuid)
   Just uuid' -> Right uuid'
   fromPersistValue x = Left $ "File.hs: When trying to deserialize a UUID: expected PersistLiteralEncoded, received: "-- >  <> T.pack (show x)
   
   instance PersistFieldSql UUID where
   sqlType _ = SqlOther "uuid"
   

   User Created Database Types

   Similarly, some databases support creating custom types, e.g. Postgres' DOMAIN and ENUM features. You can use SqlOther to specify a custom type:

   CREATE DOMAIN ssn AS text
   CHECK ( value ~ '^[0-9]{9}$');
   

   instance PersistFieldSQL SSN where
   sqlType _ = SqlOther "ssn"
   

   CREATE TYPE rainbow_color AS ENUM ('red', 'orange', 'yellow', 'green', 'blue', 'indigo', 'violet');
   

   instance PersistFieldSQL RainbowColor where
   sqlType _ = SqlOther "rainbow_color"
   

2. data PersistFilter

   esqueleto	Database.Esqueleto.Legacy

   No documentation available.

3. PersistForeignConstraintUnmet :: Text -> PersistException

   esqueleto	Database.Esqueleto.Legacy

   No documentation available.

4. PersistInt64 :: Int64 -> PersistValue

   esqueleto	Database.Esqueleto.Legacy

   No documentation available.

5. PersistInvalidField :: Text -> PersistException

   esqueleto	Database.Esqueleto.Legacy

   No documentation available.

6. PersistList :: [PersistValue] -> PersistValue

   esqueleto	Database.Esqueleto.Legacy

   No documentation available.

7. pattern PersistLiteral :: ByteString -> PersistValue

   esqueleto	Database.Esqueleto.Legacy

   This pattern synonym used to be a data constructor on PersistValue, but was changed into a catch-all pattern synonym to allow backwards compatiblity with database types. See the documentation on PersistDbSpecific for more details.

8. pattern PersistLiteralEscaped :: ByteString -> PersistValue

   esqueleto	Database.Esqueleto.Legacy

   This pattern synonym used to be a data constructor on PersistValue, but was changed into a catch-all pattern synonym to allow backwards compatiblity with database types. See the documentation on PersistDbSpecific for more details.

9. PersistLiteral_ :: LiteralType -> ByteString -> PersistValue

   esqueleto	Database.Esqueleto.Legacy

   This constructor is used to specify some raw literal value for the backend. The LiteralType value specifies how the value should be escaped. This can be used to make special, custom types avaialable in the back end.

10. PersistMap :: [(Text, PersistValue)] -> PersistValue

    esqueleto	Database.Esqueleto.Legacy

    No documentation available.

Page 494 of many | Previous | Next