2016-10-10 12:31 GMT+02:00 Heikki Linnakangas <hlinnaka@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 ?
