Re: Best method to compare subdomains

On Jan 16, 2013, at 12:23 PM, Robert James <srobertjames(at)gmail(dot)com> wrote:

> Is there a recommended, high performance method to check for subdomains?
>
> Something like:
> - www.google.com is subdomain of google.com
> - ilikegoogle.com is not subdomain of google.com
>
> There are many ways to do this (lowercase and reverse the string,
> append a '.' if not there, append a '%', and do a LIKE). But I'm
> looking for one that will perform well when the master domain list is
> an indexed field in a table, and when the possible subdomain is either
> an individual value, or a field in a table for a join (potentially
> indexed).

If you've already dealt with any punycode encoding then the lowercased,
reversed string works pretty well, either as a (probably trigger-managed)
field or as a functional index.

If you need to get fancier, you might want to take a look at the approach
https://github.com/dimitri/prefix takes.

Cheers,
Steve