Re: How to assemble all fields of (any) view into a string?

On Wed, Sep 7, 2016 at 4:39 PM, Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com>
wrote:

> On 09/07/2016 04:25 PM, Jim Nasby wrote:
>
>> On 9/7/16 6:07 PM, Ken Tanzer wrote:
>>
>>> ERROR: PL/Python functions cannot accept type record
>>>
>>
>> Ugh, yeah... that won't work. plperl might be able to do it, but I
>> suspect you're going to be stuck pulling the size info out of
>> info_schema or the catalog.
>>
>> Actually, there is a way you could hack this via plpython; pass the row
>> in as text as well as the relation (regclass is good for that). You
>> could then do plpy.execute('SELECT (%::%).*'.format(row_text,
>> relation)); that should give you a dict just like Adrian's example did.
>>
>> It would be nice if there was a function that accepted something with a
>> row descriptor and spit out the details of the descriptor.
>> http://pgxn.org/dist/colnames/doc/colnames.html comes close; if you know
>> much about C at all it shouldn't be hard to add a function to that
>> extension that returned the full details of the row. That and converting
>> the row to JSON would make it relatively easy to accomplish what you
>> want in a plpgsql (or maybe even plsql) function.
>>
>
> Getting closer:
>
> CREATE OR REPLACE FUNCTION public.str_concat(r json)
> RETURNS text
> LANGUAGE plpythonu
> AS $function$
> import json
> j = json.loads(r)
> str_out = ""
> plpy.notice(type(j))
> for col in j:
> str_out += j[col]
> return str_out
> $function$
>
> production=# select str_concat(row_to_json(t)) from str_test as t;
> NOTICE: <type 'dict'>
> CONTEXT: PL/Python function "str_concat"
> str_concat
> -----------------------
> 09/07/161234 1
>
> That's great, and was more than enough to get me started. This is what I
ended up with, which I think does the trick. Thanks so much!

CREATE OR REPLACE FUNCTION ebh_transaction_assemble( view_name varchar,
j_rec json ) RETURNS varchar LANGUAGE plpythonu AS $$
import json
j = json.loads(j_rec)
str_out = ""
query="SELECT
column_name,character_maximum_length,ordinal_position,data_type FROM
information_schema.columns WHERE table_name ='" + view_name + "' ORDER BY
ordinal_position"
cols = plpy.execute(query)
for col in cols:
dtype = col["data_type"]
dlength = col["character_maximum_length"]
dname = col["column_name"]
dvalue = str(j[dname])
if ( dvalue == "None" ) : dvalue = ""
if ( dtype == "character" ) : dvalue = dvalue.ljust(dlength)
str_out += dvalue
return str_out
$$
;

> --
> Adrian Klaver
> adrian(dot)klaver(at)aklaver(dot)com
>

--
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