Re: [HACKERS] Passing tabular data around using python functions

[Jan Urbański]

On 30/07/12 14:33, Achim Domma wrote:

Hi,


Hi Achim,

this list is meant for discussing the development of PostgreSQL, in the 
future you might want to ask your question on pgsql-general.


However, to answer your question:


I call the function like this:

select * from vectormatch(array(select (docid,conceptid,rank)::fps from fps 
where docid = 4205591))

and get the following output:

NOTICE:type 'list'
CONTEXT:  PL/Python function vectormatch
NOTICE:  ['(4205591,1,1)', '(4205591,1219,1)', ...]
CONTEXT:  PL/Python function vectormatch

I'm quite surprised that there are strings in the list and not tuples!? I tried 
my best, but I have no idea what I might be doing wrong. The main purpose of my 
sample/experiment is, to pass the results of a query to a function and to 
process it there. Any hint would be very appreciated.


Yes, it's a missing feature of PL/Python, but in your case you could 
work around it by writing your function like this:


create or replace function vectormatch(docid integer[], conceptid 
integer[], rank float4[])

returns table(docid integer, weigth float4)
as $$
data = zip(docid, conceptid, rank)
plpy.notice(data)
...
$$ language plpythonu;

and then calling it like this:

select vectormatch(array_agg(docid), array_agg(conceptid), 
array_agg(rank)) from fps where docid = 4205591;


Cheers,
Jan

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[HACKERS] Passing tabular data around using python functions

[Achim Domma]

Hi,

I'm just trying to figure out what's possible with Postgresql and Python. One 
thing that's important for me, would be to pass result sets around to process 
them further. I have a table like this:

create table fps (
docid integer,
conceptid integer,
rank float4
)

And the following function:

create or replace function vectormatch(data fps[])
returns table(docid integer, weigth float4)
as $$
plpy.notice(type(data))
plpy.notice(data)
...
$$ language plpythonu;

I call the function like this:

select * from vectormatch(array(select (docid,conceptid,rank)::fps from fps 
where docid = 4205591))

and get the following output:

NOTICE:  type 'list'
CONTEXT:  PL/Python function vectormatch
NOTICE:  ['(4205591,1,1)', '(4205591,1219,1)', ...]
CONTEXT:  PL/Python function vectormatch

I'm quite surprised that there are strings in the list and not tuples!? I tried 
my best, but I have no idea what I might be doing wrong. The main purpose of my 
sample/experiment is, to pass the results of a query to a function and to 
process it there. Any hint would be very appreciated.

cheers,
Achim
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