scheduler_changes accumulates data for Nightly schedulers when onlyIfChanged is False

[catlee]

Changes are inserted into the scheduler_changes table for processing via classify_changes, but are only retired if onlyIfChanged is True.

If onlyIfChanged is False, the rows will stay around forever. We've got 3.4 million rows in this table after running for a few months.

Fix should be simple, have the Nightly scheduler (and other timed schedulers?) avoid calling classify_changes if onlyIfChanged is False, or have it clear out any accumulated changes when it starts a build.

[dustin]

Do the calls to classify_changes and retire_changes need to be balanced?

[catlee]

In that for every classify_changes call you need exactly one retire_changes call? No, I don't think so.

Having slept on this, I don't think the Nightly scheduler should be calling classify_changes unless it knows it needs them. It should still retire any changes associated with it when it runs a build.

[catlee]

Fixed by  http://github.com/buildbot/buildbot/commit/91c884e5faee567e2dd66b65c40736e69b5c8657

Nightly no longer creates entries in scheduler_changes if onlyIfChanged is False.

It will also retire any existing entries when it runs.