Commit and unlock tables for supported backends: MySQL and PostgreSQL
Helper method to grab engine.
Obtain db_session that works with table locking
supported backends: MySQL and PostgreSQL return default session if backend not supported (eg. sqlite)
Helper method to grab session.
Return true if and only if database backend is mysql
Return true if and only if database backend is postgres
Return true if and only if database backend is sqlite
Write-lock tables for supported backends: MySQL and PostgreSQL