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class PersistStoreRead backend =>
PersistUniqueRead backendpersistent-mtl Database.Persist.Sql.Shim Queries against Unique keys (other than the id Key). Please read the general Persistent documentation to learn how to create Unique keys. Using this with an Entity without a Unique key leads to undefined behavior. A few of these functions require a single Unique, so using an Entity with multiple Uniques is also undefined. In these cases persistent's goal is to throw an exception as soon as possible, but persistent is still transitioning to that. SQL backends automatically create uniqueness constraints, but for MongoDB you must manually place a unique index on a field to have a uniqueness constraint.
class (PersistUniqueRead backend, PersistStoreWrite backend) =>
PersistUniqueWrite backendpersistent-mtl Database.Persist.Sql.Shim Some functions in this module (insertUnique, insertBy, and replaceUnique) first query the unique indexes to check for conflicts. You could instead optimistically attempt to perform the operation (e.g. replace instead of replaceUnique). However,
- there is some fragility to trying to catch the correct exception and determing the column of failure;
- an exception will automatically abort the current SQL transaction.
newtype
PersistUnsafeMigrationException persistent-mtl Database.Persist.Sql.Shim An exception indicating that Persistent refused to run some unsafe migrations. Contains a list of pairs where the Bool tracks whether the migration was unsafe (True means unsafe), and the Sql is the sql statement for the migration.
PersistUnsafeMigrationException :: [(Bool, Sql)] -> PersistUnsafeMigrationExceptionpersistent-mtl Database.Persist.Sql.Shim No documentation available.
-
persistent-mtl Database.Persist.Sql.Shim No documentation available.
-
persistent-mtl Database.Persist.Sql.Shim A raw value which can be stored in any backend and can be marshalled to and from a PersistField.
-
persistent-mtl Database.Persist.Sql.Shim No documentation available.
PersistArray :: [PersistValue] -> PersistValuepersistent-redis Database.Persist.Redis Intended especially for PostgreSQL backend for text arrays
PersistBool :: Bool -> PersistValuepersistent-redis Database.Persist.Redis No documentation available.
PersistByteString :: ByteString -> PersistValuepersistent-redis Database.Persist.Redis No documentation available.