How to delete crawled properties

You all know by now how to delete crawled properties and that you’re not able to delete a single crawled property. When deleting crawled properties, all unmapped properties from a single category get deleted.

1. In Central Administration select ‘Manage service applications’
2. Select the Search Service Application
3. Select ‘Metadata properties’
4. Select ‘Categories’
5. Edit the category of your choice
6. Select ‘Delete all unmapped crawled properties’
7. Select ‘Ok’

First thing to notice here: it deletes only unmapped crawled properties. So if your crawled property is still mapped, remove this first.

Second thing: make sure the crawled property isn’t included in the index!

First there are two crawled properties in the SharePoint category (well, there are more, I selected two to see the difference…) :

One is included in the index, the other isn’t.
Next step is to clear the SharePoint category by following all the steps above. The result:

The crawled property included in the index is still present! Even if a full index reset has been performed and the category has been cleaned up, the crawled properties doesn’t get deleted when ‘Included in index’ is set to ‘Yes’.

Summary

Besides unmapping a crawled property, deselect ‘Included in index’ in the crawled property’s properties to delete a crawled property.

This is a valid and working solution for the most of the crawled properties and certainly your custom ones.

When you’re going to test this youself, you’ll notice some of the OOTB unmapped and not include in the index crawled properties will still be present after performing the steps above. This is the case because SharePoint uses some hidden managed properties which are mapped to these crawled properties. Steve Curran explains this in his post which was written for MOSS 2007, but the same principle is still valid for SharePoint 2010:

In table MSSCrawledProperties ows_BaseName can be found with CrawledPropertyId 192.
In table MSSSchemaPropertyMappings CrawledPropertyId 192 is mapped to PID 2147418032.
In table MSSManagedProperties PID 2147418032 is mapped to property TempTitle with ‘Hidden’ and ‘NoDelete’ set to 1: