On Wed, Jul 22, 2009 at 03:03:52PM -0400, Stef Telford wrote:
> surely, please find the output attached at the bottom.
Thank you!
> Ordered by: cumulative time
>
> ncalls tottime percall cumtime percall filename:lineno(function)
> 1 0.127 0.127 83.346 83.346 sresults.py:175(__iter__)
> 40001 0.308 0.000 79.876 0.002 dbconnection.py:649(next)
Hmm. Does the program try to draw the entire table in one huge slurp?
> 40000 0.375 0.000 39.282 0.001 main.py:872(get)
> 40002 10.018 0.000 39.252 0.001 {method 'fetchone' of
> 'psycopg2._psycopg.cursor' objects}
Half of the time the program spends drawing rows one by one. This
probably could be optimized by using fetchmany or fetchall.
> 1840006 16.887 0.000 29.234 0.000 decimal.py:515(__new__)
Third of the time - Decimal.__new__. There is something strange here (in
the profiler output itself, I mean) - those Decimal calls are probably
from DecimalCol.to_python, but the profiler didn't add those calls:
> 1200000 1.856 0.000 2.769 0.000 col.py:1289(to_python)
> 3362951 2.729 0.000 2.729 0.000 main.py:1673(instanceName)
> 640000 0.999 0.000 1.471 0.000 col.py:657(to_python)
My guess is that those Decimal.__new__ calls are inside DB API driver,
and DecimalCol.to_python gets Decimal and returns it unchanged. This means
that the lines
> 40002 10.018 0.000 39.252 0.001 {method 'fetchone' of
> 'psycopg2._psycopg.cursor' objects}
> 1840006 16.887 0.000 29.234 0.000 decimal.py:515(__new__)
should be read as follows: fetchone draws a row and converts values to
Decimal, so 29.2 s are really a part of 39.2, and fetchone only waited for
DB for 10 seconds.
> 40000 0.214 0.000 23.323 0.001 main.py:912(_init)
> 40000 10.475 0.000 23.069 0.001 main.py:1140(_SO_selectInit)
_SO_selectInit is a rather simple function - it populates the row with
values just fetched from the DB; the values are converted using calls to
to_python. Those to_python calls are fast (if we ca believe the profiler) -
see above. So where does _SO_selectInit spend its time?!
Oleg.
--
Oleg Broytmann http://phd.pp.ru/ [email protected]
Programmers don't die, they just GOSUB without RETURN.
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