CrossListQueryInfo and CrossListQueryCache gotchas

CrossListQueryInfo class which comes with the Microsoft Publishing infrastructure makes use of object caching techniques to query the requested data from the cache instead from the database. Remember to use this facility only if your code runs against a MOSS server and not on a WSS server. As this makes use of  object cache stored in WFE servers, it avoids to database input/output and network latency between the WFE's and database server.

Although it uses SPSiteDataQuery internally,the very first request using CrossListQueryCache takes more time than SPSiteDataQuery. Practically it includes the time for querying, caching and returning the values. But subsequent queries fetch results in a flash and no where comparable with SPSiteDataQuery.

Interesting fact is that this CrossListQueryCache and QueryInfo will not work in a Console line tool, it badly depends on the context. If you are really trying this interesting query technique in a web part, whenever you implement any change in your webpart and trying to debug. Apart from doing the IISReset/App pool recycle, don't forget to flush the object cache

A sample CrossListQueryCache

public DataTable GetDataTableUsingCrosslistQuery(SPSite site)
{
CrossListQueryInfo clquery = new CrossListQueryInfo();
clquery.RowLimit = 100;
clquery.WebUrl = site.ServerRelativeUrl;
clquery.UseCache = true ;
clquery.Lists = "";
clquery.Webs = "";
//clquery.Query = "";
clquery.Query = "569";
clquery.ViewFields = "";
CrossListQueryCache cache = new CrossListQueryCache(clquery);
DataTable results = cache.GetSiteData(site);
return results; 
}