Unfortunately, there's no PowerShell-command to delete/remove a single crawled property in FAST (nor is there one in SharePoint, as is stated by Corey Roth). In most cases, there's no need for such a command. However, when you're "experimenting" in a development environment, the list of debug/test/dummy crawled properties might become very long and the need to clean up the place might arise. It would've been nice if Microsoft offered the Remove-FASTSearchMetadataCrawledProperty command, in addition to the already available Get-, New-, Set- commands, but sadly, we'll have to do without this.
There is, however, a way to get rid of all unused/unmapped crawled properties all at once. You can either do this through the UI in Central Administration. Just go to your FAST Query Service Application > FAST Search Administration > Crawled Property Categories > [category-that-needs-cleaning] > Edit Category > Check "Delete all unmapped crawled properties" > Hit OK:
If you're more into scripting your configuration/deployment, there's also a nice way to do this through PowerShell. Just start up your FAST Search Server 2010 for SharePoint PowerShell window and run:
$category = Get-FASTSearchMetadataCategory -Name "[category-that-needs-cleaning]"
$category.DeleteUnmappedProperties()
There is, however, a way to get rid of all unused/unmapped crawled properties all at once. You can either do this through the UI in Central Administration. Just go to your FAST Query Service Application > FAST Search Administration > Crawled Property Categories > [category-that-needs-cleaning] > Edit Category > Check "Delete all unmapped crawled properties" > Hit OK:
If you're more into scripting your configuration/deployment, there's also a nice way to do this through PowerShell. Just start up your FAST Search Server 2010 for SharePoint PowerShell window and run:
$category = Get-FASTSearchMetadataCategory -Name "[category-that-needs-cleaning]"
$category.DeleteUnmappedProperties()
