postgresql-simple-0.3.3.1: Mid-Level PostgreSQL client library

Safe HaskellNone

Database.PostgreSQL.Simple.Errors

Description

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

Note: Success of parsing may depend on language settings.

Synopsis

Documentation

data ConstraintViolation Source

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

constraintViolation :: SqlError -> Maybe ConstraintViolationSource

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)Source

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 aSource

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