Database.PostgreSQL.Simple.Errors

| Module for parsing errors from postgresql error messages. Currently only parses integrity violation errors (class 23).

Note: Success of parsing may depend on language settings.

Documentation

data ConstraintViolation

Constructors

NotNullViolation ByteString

The field is a column name

ForeignKeyViolation ByteString ByteString

Table name and name of violated constraint

UniqueViolation ByteString

Name of violated constraint

CheckViolation ByteString ByteString

Relation name (usually table), constraint name

Instances

Eq ConstraintViolation

Ord ConstraintViolation

Show ConstraintViolation

Typeable ConstraintViolation

Exception ConstraintViolation

constraintViolation :: SqlError -> Maybe ConstraintViolation

Tries to convert SqlError to ConstrainViolation, checks sqlState and succeedes only if able to parse sqlErrorMsg.

 createUser = catchJust constraintViolation catcher $ execute conn ...
   where
     catcher UniqueViolation "user_login_key" = ...
     catcher _ = ...

constraintViolationE :: SqlError -> Maybe (SqlError, ConstraintViolation)

Like constraintViolation, but also packs original SqlError.

 createUser = catchJust constraintViolationE catcher $ execute conn ...
   where
     catcher (_, UniqueViolation "user_login_key") = ...
     catcher (e, _) = throwIO e

catchViolation :: (SqlError -> ConstraintViolation -> IO a) -> IO a -> IO a

Catches SqlError, tries to convert to ConstraintViolation, re-throws on fail. Provides alternative interface to catchJust

 createUser = catchViolation catcher $ execute conn ...
   where
     catcher _ (UniqueViolation "user_login_key") = ...
     catcher e _ = throwIO e

isSerializationError :: SqlError -> Bool

isNoActiveTransactionError :: SqlError -> Bool

isFailedTransactionError :: SqlError -> Bool