On Wed, Jul 22, 2009 at 05:18:46PM -0400, Stef Telford wrote:
>>> 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?
>>
> Actually, no. This page does 40k of bookings (a single object type) but
> the query isn't "Sequential" (it's not grabbing 0-40,000 is what I
> mean).
Hmm. One call to SelectResults.__iter__ that spans the entire program's
lifetime. "One huge SELECT" is the only way I can interpret this.
> I can do a page which has lots of different object types if this
> would help ?
I doubt that would make difference.
>>> 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.
>>
> Noted. Let me try this later tonight when I have some spare cycles :)
It's not that easy. Changing fetchone to fetchmany required an additional
loop over the results in Iteration.next - similar to what I did in
InheritableIteration.next.
>> 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.
>>
> 10seconds to fetch from the database is not bad (in my view). The 29s
> for decimal is definitely 'killer'
So we have 29 seconds in Decimal.__new__, 10 seconds in fetchone, and 23
seconds in _SO_selectInit. 63 seconds of 85...
>>> 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?!
Well, it is certainly not evals. I also doubt it has something with
garbage collection. Not in this function.
Oleg.
--
Oleg Broytmann http://phd.pp.ru/ [email protected]
Programmers don't die, they just GOSUB without RETURN.
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