https://bugzilla.wikimedia.org/show_bug.cgi?id=39519

Markus Krötzsch <[email protected]> changed:

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--- Comment #1 from Markus Krötzsch <[email protected]> 2012-08-21 
07:56:32 UTC ---
It is known that there can be large numbers of small SQL queries in some
configurations. We are working on improving the in-memory caching to
significantly reduce this (it is also known that getSMWPageIDandSort is the
main reason for this problem).

Please note that the queries that are run on one page view may not belong to
one page only. MediaWiki has a system of background jobs that refresh other
pages in small batches when you view one. This can explain queries that appear
completely unrelated to the page that you view. To get reliable query logs for
one particular page, you should first empty your job queue (can be processed
via a command line script of MW) or (better yet) temporarily disable jobs to be
run while pages are viewed.

Overall, however, I have only seen such large query logs on sites that used
exceedingly complex template structures in combination with #ask or #show.
Typical setups included "all you can know" templates that check for the
presence of all kinds of data that they will then show. The extreme case of
this design is to have one generic infobox template for all, using queries and
parser functions to customise its look for various types of pages. Such a
design is rarely a good idea; besides the efficiency issues, it also leads to
extremely complex templates that are hard to maintain. Symptomatic for this
semantic wiki anti-pattern are also auxiliary templates that are used as macros
in many places, and which are using many queries themselves (e.g., a template
that creates a table line for a property value, but only if the property has
some value, and possibly picking different formats depending on the number of
values that the property has). Such sub-templates are then often overused in
places where it is already clear how many values a property should have.
Another performance killer is template-based result formatting in #ask, esp. if
the template itself uses queries. This particular design leverages SMW itself
to create large numbers of queries and templates on one page. One can improve
performance by revisiting such designs and reworking template structures to be
more streamlined. I don't know if any of this applies to your site, of course.

Which version of SMW exactly are you using? Do you have special settings for
$smwgDefaultStore in your LocalSettings? Please also provide a link to the page
that creates the problems for you, or give a detailed description of its
contents, including the templates that it uses.

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