Atomicity of PostgreSQL Interactions

Both the webapi and the node which populates the database operate on the database within a database transaction. All operations on the database from Haskell code is done in a function which has a type signatures of :

ReaderT SqlBackend m a

Any function without the ReaderT SqlBackend component will not be able to access the database and any attempt to access the database without the required type signature will result in a compile error at compile time.

All functions with the required file type are run with the function provided by Haskell’s Persistent library:

runSqlConnWithIsolation action backend Serializable


  • runSqlConnWithIsolation is the function that runs the provided action on a connection to the database within a database transaction.

  • action is the action to be performed on the database (eg write or query).

  • backend contains the database connection data.

  • Serializable specifies the transaction isolation level.

In this case the Serializable transaction isolation level is used which is the maximum level of transaction isolation.