Re: [HACKERS] libpq Alternate Row Processor

On 2/8/17 5:11 PM, Kyle Gearhart wrote:
> Overall, wall clock improves 24%.  User time elapsed is a 430% improvement.  About half the time is spent waiting on
theIO with the callback.  With the regular pqRowProcessor only about 16% of the time is spent waiting on IO.
 

To wit...
    real    user    sys
single row    0.214    0.131    0.048
callback    0.161    0.030    0.051

Those are averaged over 11 runs.

Can you run a trace to see where all the time is going in the single row 
case? I don't see an obvious time-suck with a quick look through the 
code. It'd be interesting to see how things change if you eliminate the 
filler column from the SELECT.

Also, the backend should be buffering ~8kb of data before handing that 
to the socket. If that's more than the kernel can buffer I'd expect a 
serious performance hit.
-- 
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
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