No ContentClass specified on search results (after full or incremental crawls)

Dear StackOverflow members,

I'm currently facing an issue with one of my SharePoint server, the contentclass assigned to the crawled content is never set.

I noticed that when my scopes returned 0 result (I'm filtering on contentclass=sts_list_item_开发者_StackOverflow850). A quick search with the neat ZevenSea SearchCoder within the crawled content confirmed this

(no content class is available, field is empty accross all crawled content).

I deleted my scopes, did a full crawl, even deleted my SSP and create a new one, running the configuration wizard but this behavior is still here and I've no clue why it's the case.

If you have any idea what could be the culprit, I'm eager to know.

Thanks a lot for any feedback.

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I also had the same issue and I noticed that in the search schema the mappings of the managed property were not complete. I added all the mappings in the correct order and the issue has gone (I copied mapping and order from a farm where it was working well).