Hey guys... posting this question from my technical team.
We're experiencing a significant wordpress site performance problem with the WPMU domain mapping plugin.
Running on a WP multisite with several hundred sites, many of which are domain mapped.
When the domain mapping plugin is network enabled, the wordpress admin drags… just has a couple seconds of lag for every page view.
We installed the wordpress "Debug Bar" plugin to track down the source of the slowness - http://wordpress.org/plugins/debug-bar/
and found that for every single page view in wordpress admin in the multisite (top level wp admin OR sub-site admin) - a HUGE query is added when domain mapping is network enabled… this query is hundreds of lines long, and I don't understand its purpose… seems to contain many references to each site in the multisite…
when I network disable the domain mapping plugin, this query disappears and the wordpress admin responds noticeably faster.
Here's how to enable debug in your wordpress to see the SQL queries on a page with the Debug Bar: http://www.screencast.com/t/hKDFcAp68
Then just navigate to your wordpress admin and click the red "debug" link at the top right, then click "queries" on the left and scroll a bit till you see the giant one…
Here are our domain mapping settings: http://www.screencast.com/t/ts4V1IV3tGS
Changing these both to "original domain" had no effect on getting rid of that gigantic query…
How can we get rid of that gigantic query that's impacting literally every single page view to wordpress admin?