Re: Endless loop calling PL/Python set returning functions

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Alexey Grishchenko <agrishchenko(at)pivotal(dot)io>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Endless loop calling PL/Python set returning functions
Date: 2016-03-10 17:20:32
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Alexey Grishchenko <agrishchenko(at)pivotal(dot)io> writes:
> No, my fix handles this well.
> In fact, with the first function call you allocate global variables
> representing Python function input parameters, call the function and
> receive iterator over the function results. Then in a series of Postgres
> calls to PL/Python handler you just fetch next value from the iterator, you
> are not calling the Python function anymore. When the iterator reaches the
> end, PL/Python call handler deallocates the global variable representing
> function input parameter.

> Regardless of the number of parallel invocations of the same function, each
> of them in my patch would set its own input parameters to the Python
> function, call the function and receive separate iterators. When the first
> function's result iterator would reach its end, it would deallocate the
> input global variable. But it won't affect other functions as they no
> longer need to invoke any Python code.

Well, if you think that works, why not undo the global-dictionary changes
at the end of the first call, rather than later? Then there's certainly
no overlap in their lifespan.

regards, tom lane

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