Monad classes for running queries with Persistent and Esqueleto.

This package introduces two classes: MonadSqlBackend for monadic contexts in which a SqlBackend is available, and MonadSqlBackend for contexts in which we can execute a SQL transaction.

Additionally, this package provides variants of query-running utilities from Persistent and Esqueleto which are concretized to use SqlBackend, generalized to a MonadSqlBackend m constraint rather than "ReaderT backend", and wrapped in checkpointCallStack so that exceptions will include call stacks.

persistent-sql-lifted

This package introduces two classes:

• MonadSqlBackend m, for monadic contexts m in which a SqlBackend is available

• MonadSqlBackend db m, for monadic contexts m in which we can execute a SQL transaction of type db a and get a result m a. (The type db should have an instance of `MonadSqlBackend.)

Additionally, this package provides variants of query-running utilities from persistent and esqueleto which are

1. Concretized to use SqlBackend;
2. Generalized to a MonadSqlBackend m constraint rather than ReaderT backend m;
3. Wrapped in checkpointCallStack so that exceptions will include call stacks.

How to migrate from vanilla persistent/esqueleto:

• Instead of SqlPersistT, use a MonadSqlBackend constraint.

• Define an instance of MonadSqlTx for your application Monad that specifies how your application runs database transactions, e.g. by running runSqlPool.

• Instead of calling runSqlPool directly from the rest of your application code, use the runSqlTx method from the MonadSqlTx class.