Mattio, I would not disable merges. Ever*.
First, merges are a good thing. You can think of them as the server automatically optimizing its indexes. Merges will happen as the result of any update, including add, update, delete, reindex, and refragment. Merges are there to keep the system performance good, even in the midst of many updates. When we size systems, we take into consideration the typical update loads so that merges don't have to compete with other processing. It sounds as if either your system is undersized, or you're in a situation where you're doing more work than is typical. I'm guessing it is the latter. Merges need to happen, and while it is possible to delay them, eventually they need to take place. The default settings for merges are typically the optimal configuration for performing the least number of merges while maintaining good performance. In production systems, we sometimes recommend that merges be limited to a maximum size during peak usage. The larger the merge, the longer the merge process takes. By limiting merge size to 500MB, for example, you are reducing the number of large merges, and therefore delaying the optimization until a later time when system resources are less precious. When updating the majority or all of a database, it is oftentimes faster to reload the documents into an empty database. However, this may not be feasible for you, in which case the fastest thing may be to simply let your query run without changing any of your merge settings. Kelly * There may be a reason why you would want to disable merges, but I'm having a hard time coming up with one. -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Friday, August 14, 2009 3:00 PM To: [email protected] Subject: General Digest, Vol 62, Issue 34 Send General mailing list submissions to [email protected] To subscribe or unsubscribe via the World Wide Web, visit http://xqzone.com/mailman/listinfo/general or, via email, send a message with subject or body 'help' to [email protected] You can reach the person managing the list at [email protected] When replying, please edit your Subject line so it is more specific than "Re: Contents of General digest..." Today's Topics: 1. Disabling merges during a large update (Mattio Valentino) ---------------------------------------------------------------------- Message: 1 Date: Fri, 14 Aug 2009 13:46:02 -0400 From: Mattio Valentino <[email protected]> Subject: [MarkLogic Dev General] Disabling merges during a large update To: General Mark Logic Developer Discussion <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1 We've been doing some query tuning and updating of our documents to get some better performance. One of the issues we're running into is that we have merges happening at the same time as reindexing/refragmenting, so everything slows down noticeably. I have another wide-spread update to make (to fix my namespace issues from an earlier email). The database has two forests and 16 stands now (currently mid-merge) and it is not in production. Is it safe to disable merges while my update is running and then re-enable them after it is complete? The details in the Administrator's Guide seem to indicate this would be okay in my scenario, but I thought I'd throw this one out to the group. Thanks, Mattio ------------------------------ _______________________________________________ General mailing list [email protected] http://xqzone.com/mailman/listinfo/general End of General Digest, Vol 62, Issue 34 *************************************** _______________________________________________ General mailing list [email protected] http://xqzone.com/mailman/listinfo/general
