[Labs-l] Performance of crosswiki query tools

[Jesse (Pathoschild)]

Hello,

I noticed a performance issue with tools that query data from many wikis. I
open connections to each DB slice, then do a "use `dbname`" to switch to
each wiki for the relevant queries. This is *very* slow on Tools Labs; does
the Tools Labs infrastructure make "use `dbname`" significantly slower? Is
there a more efficient way to do this?

I created a simple script which reproduces the issue. It runs in 0.3
seconds on the Toolserver<https://toolserver.org/~pathoschild/accounteligibility/test.php>(
source <http://pastebin.com/ctUQsXZm>), but takes a whopping 23 seconds on
Tools Labs<http://tools.wmflabs.org/pathoschild-contrib/accounteligibility/test.php>(
source <http://pastebin.com/Xi3abGFP>). The scripts shows the profiling
results at the bottom of the page (click the [+] next to "*Page generated
in XX seconds*").

-- 
Jesse Plamondon-Willard (Pathoschild)
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