On 5/23/13 7:34 PM, Claudio Freire wrote:
Why not make the delay conditional on the amount of concurrency, kinda
like the commit_delay? Although in this case, it should only count
unwaiting connections.

The test run by commit_delay is way too heavy to run after every block is processed. That code is only hit when there's a commit, which already assumes a lot of overhead is going on--the disk flush to WAL--so burning some processing/lock acquisition time isn't a big deal. The spot where statement delay is going is so performance sensitive that everything it touches needs to be local to the backend.

For finding cost delayed statements that are causing trouble because they are holding locks, the only place I've thought of that runs infrequently and is poking at the right data is the deadlock detector. Turning that into a more general mechanism for finding priority inversion issues is an interesting idea. It's a bit down the road from what I'm staring at now though.

Greg Smith   2ndQuadrant US    g...@2ndquadrant.com   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.com

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