Test script for transaction concurrency for postgr

问题:

I would like to test some variants of transaction concurrency in PostgreSQL and for that I need a script which would force two transaction to start at exactly the same time. Something that does not requires manual intervention ;) Any ideas?

回答1:

You can homebrew this by taking a LOCK on a table, setting up your transactions, then releasing the lock by rolling back the transaction that got the lock. See this prior answer and its links for details on this approach. While I demonstrated it using three psql sessions it's equally viable to do it with bash co-processes, a Python script using psycopg2 and the multiprocessing or threading modules, etc. Fairly simple to do. Update: In fact here's an example I just wrote in python3.

For more sophisticated tests, grab the PostgreSQL source code and use the "isolationtester" tool in src/test/isolation which lets you write recipes that do complex orderings of commands. It doesn't support being built with PGXS (though such support would probably be pretty trivial to add) so you have to compile the whole PostgreSQL source tree, but that's quick enough. It'll run against your existing PostgreSQL so there's no need to install the one you compiled.

See src/test/isolation/README for more about the isolationtester tool. The docs are a little thin on the ground since it's an internal testing tool, but the existing tests cases should help you get started. Feel free to improve it to meet your needs and submit patches :)