Re: improve type conversion of SPI_processed in Python

On 1/9/18 15:54, Tom Lane wrote:
> Peter Eisentraut <peter.eisentraut@2ndquadrant.com> writes:
>> Here is a patch to improves how PL/Python deals with very large values
>> of SPI_processed.  The previous code converts anything that does not fit
>> into a C long into a Python float.  But Python long has unlimited
>> precision, so we should be using that instead.  And in Python 3, int and
>> long as the same, so there is no need to deal with any variations anymore.
> 
> I took a quick look at this.  +1 for returning Python long all the time,
> but I wonder why the Python version dependency.

To keep returning an int in Python 2 in the cases it fits.  Maybe that's
overkill.

> Our existing function
> PLyLong_FromInt64() believes that PyLong_FromLongLong is unconditionally
> available.

Interesting.  I had coded this to account for the possibility that long
long does not exist on a 64-bit platform, but that situation probably
died with the first Alpha or something.

> I'd be inclined to code PLyObject_FromUint64() as an exact
> analog of PLyLong_FromInt64(), ie
> 
> 	/* on 32 bit platforms "unsigned long" may be too small */
> 	if (sizeof(uint64) > sizeof(unsigned long))
> 		return PyLong_FromUnsignedLongLong(DatumGetUInt64(d));
> 	else
> 		return PyLong_FromUnsignedLong(DatumGetUInt64(d));
> 
> and let Python worry about how to optimize the conversion.

Would that even be necessary?  Why not use the LongLong variant all the
time then?

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
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