MarkLogic Cookbook

Chapter 1. Peak Performance

Many MarkLogic installations store large amounts of data, but still provide fast searches. The key to performance is understanding how MarkLogic works—specifically understanding query and update modes, and the use of indexes. These two recipes help ensure you’re getting the speed you need for your applications.

Assert Query Mode

Problem

All MarkLogic requests run in either query or update mode, based on a static analysis of the code. The mode is important, because query requests are able to run without locking database content. Accidentally running in update mode is a common cause of requests running slower than expected.

Verify that a MarkLogic statement is running in query mode.

Solution

Applies to MarkLogic versions 7 and higher

Place this snippet as early in the code path as you can to make sure it is executed before MarkLogic spends too much time on other parts of your request:

let $assert-query-mode as xs:unsignedLong :=
  xdmp:request-timestamp()

If a request that includes this line is run in update mode, then this error will be thrown:

> XDMP-AS: (err:XPTY0004) let $assert-query-mode as
xs:unsignedLong := xdmp:request-timestamp() -- Invalid coercion:
() as xs:unsignedLong

Discussion

Sometimes MarkLogic’s static analysis may see something that triggers update mode, even if that was not the developer’s intent. The code in this recipe will throw an exception if it is run as an update, making it easy to notice the problem. Once this problem ...