[MarkLogic Dev General] Peformance issue (Merging) - XDMP:node-replace function

[Michael Blakeley]

Deshbir,

You can learn more about merges by reading our admin guide, available 
via http://developer.marklogic.com/pubs

Merges are asynchronous with respect to queries, but they can compete 
with queries for system resources. I suspect that's a false trail, though.

How large is the document on which node-replace is running? If you do 
see a that ErrorLog extract after every node-replace, that suggests a 
document size of 5-20 MB. If so, you should consider breaking up your 
documents into smaller ones, or possibly use a fragment root or fragment 
parent (fragments are also discussed in the admin guide).

-- Mike

On 2009-03-16 04:06, deshbir.dugal at comprotechnologies.com wrote:
> Hello,
>
> We are experiencing extremely slow XQUERY performance for the XDMP:node-replace function. Following is an XQUERY snippet that consistently takes more than 5 secs on one of our servers (Mark Logic 3.2).
> ============================================
> let $docbookNode :=<p>hello</p>
> let $path := doc(".....")/../../
> return
> 	xdmp:node-replace($path,$docbookNode)
> ============================================
> On another (different) Mark Logic installation (3.2), the same code takes consistently less that 300 milliseconds!
>
> We've compared the server settings and they appear to be the same across both servers (they are probably the default Mark Logic installation settings)
>
> On examining the log folder, we found that every time an "xdmp:node-replace" was executed, the following lines are being added to the error log file:
> ============================================
> 2009-03-16 06:45:32.114 Info: Saving C:\Program Files\MarkLogic\Data\Forests\Documents\00000470
> 2009-03-16 06:45:32.880 Info: Saved 15 MB in 1 sec at 15 MB/sec to C:\Program Files\MarkLogic\Data\Forests\Documents\00000470
> 2009-03-16 06:45:33.036 Info: Merging 62 MB from C:\Program Files\MarkLogic\Data\Forests\Documents\0000046f and C:\Program Files\MarkLogic\Data\Forests\Documents\00000470 to C:\Program Files\MarkLogic\Data\Forests\Documents\00000471
> 2009-03-16 06:45:37.661 Info: Merged 55 MB in 5 sec at 11 MB/sec to C:\Program Files\MarkLogic\Data\Forests\Documents\00000471
> 2009-03-16 06:45:37.958 Info: Deleted C:\Program Files\MarkLogic\Data\Forests\Documents\0000046f
> 2009-03-16 06:45:38.098 Info: Deleted C:\Program Files\MarkLogic\Data\Forests\Documents\00000470
> ============================================
>
> What is going wrong here? What could be causing all the "merging" activity?
>
> Thanks in advance.
>
> Regards,
> Deshbir
>
>
>
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