title: Speeding up checking of IP address membership in CIDR ranges, for large datasets
body: <p>In a Postgres DB, I need to filter a set of several hundred thousand rows in a table A by including only those rows for which an IP address column (of type inet) in the row matches any of several thousand IP address blocks (of type cidr) in another table B. I've tried various indexes on the inet addresses in the first table and the cidr ranges in the second, but no matter what I do, the planner does a nested sequential scan, applying the &lt;&lt; operator to every pair of IP addresses and prefixes.</p>
  
  <p>Is there a way to speed this up with indexes or other clever tricks? (I can resort to external procedural scripting, but I was wondering if it's doable within Postgres.)</p>
  
  <p>Thanks!</p>