Fast Search managed properties text as integer

Question

Im trying to search on the managed property numcomments. This property is the number of comments stored for a blog post. The proprty is a text field which means if im also sorting by it, 11 comes before 2.
Ive tried to create a new manage property mapping to comments but storing it as an integer. No results are showing in search when i search by this new managed property term.
Is there a way to store text data, in an integer search managed property. I think the reason why ows_comments is a text field instead of a integer might have something to do with it being a lookup column.
I really need to call a keyword search in code and sorting by numcomments correctly. Can anyone suggest anything?

Answer 1

You have to use a pipeline extensibility stage which reads the text based property and writes it back to a new crawled property of type int, which you can map to an int based managed property.

I've done the same for date <meta> tags in web pages which are interpreted as text, but you want them as dates.

I have a powershell prototype sample here which you can use as a basis to test this: http://techmikael.blogspot.se/2011/03/prototyping-pipeline-stages-in.html