On 10 October 2016 at 13:42, Pavel Stehule <pavel.steh...@gmail.com> wrote:
> > > 2016-10-10 12:31 GMT+02:00 Heikki Linnakangas <hlinn...@iki.fi>: > >> On 10/01/2016 02:45 AM, Jim Nasby wrote: >> >>> On 9/29/16 1:51 PM, Heikki Linnakangas wrote: >>> >>>> Now, back to multi-dimensional arrays. I can see that the Sequence >>>> representation is problematic, with arrays, because if you have a python >>>> list of lists, like [[1, 2]], it's not immediately clear if that's a >>>> one-dimensional array of tuples, or two-dimensional array of integers. >>>> Then again, we do have the type definitions available. So is it really >>>> ambiguous? >>>> >>> >>> [[1,2]] is a list of lists... >>> In [4]: b=[[1,2]] >>> >>> In [5]: type(b) >>> Out[5]: list >>> >>> In [6]: type(b[0]) >>> Out[6]: list >>> >>> If you want a list of tuples... >>> In [7]: c=[(1,2)] >>> >>> In [8]: type(c) >>> Out[8]: list >>> >>> In [9]: type(c[0]) >>> Out[9]: tuple >>> >> >> Hmm, so we would start to treat lists and tuples differently? A Python >> list would be converted into an array, and a Python tuple would be >> converted into a composite type. That does make a lot of sense. The only >> problem is that it's not backwards-compatible. A PL/python function that >> returns an SQL array of rows, and does that by returning Python list of >> lists, it would start failing. >> > > is not possible do decision in last moment - on PL/Postgres interface? > There the expected type should be known. > > Regards > > Pavel > > >> >> I think we should bite the bullet and do that anyway. As long as it's >> clearly documented, and the error message you get contains a clear hint on >> how to fix it, I don't think it would be too painful to adjust existing >> application. >> >> We could continue to accept a Python list for a plain composite type, >> this would only affect arrays of composite types. >> >> I don't use PL/python much myself, so I don't feel qualified to make the >> call, though. Any 3rd opinions? > > Can't you determine the correct output based on the function output definition ? For instance if the function output was an array type then we would return the list as an array if the function output was a set of then we return tuples ? Dave Cramer da...@postgresintl.com www.postgresintl.com
