As a suggestion for 5.0 having a scripted DB migration system would make upgrading much
easier.
Something like what Asterisk now uses (Alembic
https://pypi.python.org/pypi/alembic) would
be ideal, as it works in a DB agnostic manner and you would just have to ensure that there
is a driver for the DB you wish to use.
That way you would just update the definition script and select the target when you run
the updater, and would allow kamailio a greater choice in backing DB's as once the
script is written assuming a driver is available for you RDBMS the schema would be
successfully ported.
This would do away with maintaining separate MySQL, Postgres, Oracle, MSSQL scripts as
well.
The only issue I can think with a system like this is in the situation where hardcoded SQL
strings are in the source and use a RDBMS specific function as that could cause some
"fun" in debugging...