On Tue, Nov 22, 2011 at 12:19 AM, Stephen Powis <stephen.po...@pardot.com> wrote: > Just trying to get a better understanding of this.....Wouldn't the indexes > not being in the disk cache make the queries themselves slow as well (high > qTime), not just fetching the results?
What happens in situations like this is that the true "index" portions that are being used more often get cached by the OS, but the stored fields aren't. Also, use of the index portion normally consists of sequential IO, which is more efficient if not cached (i.e. iterating over all doc ids that match a term). But after the top N documents are found, if the stored fields aren't in cache, it's a disk seek for each document being returned. This is normally only tolerable if you're only retrieving the top 10 documents or so. -Yonik http://www.lucidimagination.com
