In my experimentation with tile rendering, I often want to rerender only a subset of the tiles that I've previously rendered, usually because I've changed parameters just for secondary roads or something similar.

To facilitate that, I wrote a script: expire-query. It takes an SQL query (or queries) as a parameter, runs the query, and lists the tiles covered by the results of the query in the same format that osm2pgsql does (so any tools that operate on those files will work with this script, too).

To run it, you'll need Ruby, Rubi DBI, and the PostgreSQL Ruby DBI driver (which is included in the Ruby DBI distribution).

The --help option should cover any usage questions.