Crawling a Microsoft Sharepoint 2007 list or document library might fail with timeout, or Site Data Web Service "Out of Memory" error in the crawl log, if the list or document library contains several hundred columns

Source: Microsoft Support

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Although Sharepoint’s internal structure can handle thousands of columns in a list or document library, (as documented in Technet article http://technet.microsoft.com/en-us/library/cc287790.aspx) without having a performance impact, Sharepoint’s search engine might fail crawling these structures.

If there are no search results for a list or document library with a lot of columns, and in the crawl log you see either a Site Data Web Service, Out of memory, or Timeout error, you may be experiencing this problem.

The Site Data Web Service error appears if you have a Sharepoint build before the 2008 October rollup.

There is no hard limit when this error could occur, it largely depends on the columns types, and the capacity of the SQL backend.

October 2008 and later rollups can handle a larger query, and if the SQL backend is capable of calculating the query, the crawler will work.

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