Re: [GENERAL] JSON to INT[] or other custom type
On 11/06/17, Bruno Wolff III (br...@wolff.to) wrote: > On Sun, Jun 11, 2017 at 22:35:14 +0100, > Rory Campbell-Langewrote: > > > >I'm hoping, in the plpgsql function, to unfurl the supplied json into a > >custom type or at least an array of ints, and I can't work out how to do > >that. > > > > select * from json_array_elements_text('[[0, 1], [1, 2]]'); > >value > > > >[0, 1] > >[1, 2] > > (2 rows) > > > >works fine, but I can't seem to turn those values into actual ints or > >anything else for that matter, apart from text via the > >json_array_elements_text() function. > > Does this example help? > > area=> select (a->>0)::int, (a->>1)::int from json_array_elements('[[0, 1], > [1, 2]]') as s(a); > int4 | int4 --+-- >0 |1 >1 |2 > (2 rows) Hi Bruno That worked great, thank you very much for the pointer. I completely failed to see the top of the docs at https://www.postgresql.org/docs/9.5/static/functions-json.html -- my apologies. I've put a working function and caller from PHP, Python below. Many thanks Rory /* plpgsql test function */ CREATE OR REPLACE FUNCTION fn_test05 ( num INT ,ds json ) RETURNS SETOF dow_session AS $$ DECLARE r test.dow_session; BEGIN RAISE NOTICE 'num: %', num; FOR r IN SELECT (n->>0)::int -- first json element ,(n->>1)::int FROM json_array_elements(ds) AS x(n) LOOP RETURN NEXT r; END LOOP; RETURN; END; $$ LANGUAGE plpgsql; ## python example import psycopg2 import json dbc = psycopg2.connect(database=, user=, password=) cur = dbc.cursor() query = 'select * from test.fn_test05(%s, %s)' a_of_a = json.dumps([(0,2), (3,1), (5,2)]) qargs = (5, a_of_a) cur.execute(query, qargs) rs = cur.fetchall() for r in rs: print r # (0, 2) # (3, 1) # (5, 2) ## php example user= password="); $query = 'select * from test.fn_test05($1, $2)'; $result = pg_query_params($dbconn, $query, array($a, $j)); print_r(pg_fetch_all($result)); # Array # ( # [0] => Array # ( # [dow] => 0 # [session] => 1 # ) # # [1] => Array # ( # [dow] => 2 # [session] => 3 # ) # ) ?> -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
Re: [GENERAL] JSON to INT[] or other custom type
On Sun, Jun 11, 2017 at 2:35 PM, Rory Campbell-Lange < r...@campbell-lange.net> wrote: > I'm hoping, in the plpgsql function, to unfurl the supplied json into a > custom type or at least an array of ints, and I can't work out how to do > that. You will be unable to cast the array itself. You must use json functions to unfurl the json into a result set with each row containing a single value. You can then explicitly cast that value to integer. If the casting doesn't fail you now have column of integers that can be "array_agg(value_as_integer)" to construct an SQL array of type integer[] (or whatever you decide to cast it to). You can write you own pl/pgsql function to do these operations. As your example includes a two-dimensional array you probably will need to json_array_elements_text twice, then array_agg twice, to get a similar structure in the eventual SQL array. Hopefully that moves you in a useful direction. David J.
Re: [GENERAL] JSON to INT[] or other custom type
On Sun, Jun 11, 2017 at 22:35:14 +0100, Rory Campbell-Langewrote: I'm hoping, in the plpgsql function, to unfurl the supplied json into a custom type or at least an array of ints, and I can't work out how to do that. select * from json_array_elements_text('[[0, 1], [1, 2]]'); value [0, 1] [1, 2] (2 rows) works fine, but I can't seem to turn those values into actual ints or anything else for that matter, apart from text via the json_array_elements_text() function. Does this example help? area=> select (a->>0)::int, (a->>1)::int from json_array_elements('[[0, 1], [1, 2]]') as s(a); int4 | int4 --+-- 0 |1 1 |2 (2 rows) -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
[GENERAL] JSON to INT[] or other custom type
I'm playing with plpgsql function parameters to try and come up with a neat way of sending an array of arrays or array of custom types to postgres from python and PHP. Psycopg works fine with an array of custom types: In [108]: query = 'select * from fn_test03(%s, %s::dow_session[])' In [109]: qargs = (5, [(0,2), (1, 3)]) In [110]: cur.execute(query, qargs) In [111]: rs = cur.fetchall() # function plays back looped arrays In [112]: rs Out[112]: [(0, 2), (1, 3)] However PHP's Postgresql support isn't very array friendly as far as I can see, and requires some horrible manual escaping. Consequently I wondered if I could serialise the array structure into json and send that to the postgresql function. PHP seems to handle that fine. My problem therefore move to handling the json in the plpgsql function. I'm hoping, in the plpgsql function, to unfurl the supplied json into a custom type or at least an array of ints, and I can't work out how to do that. select * from json_array_elements_text('[[0, 1], [1, 2]]'); value [0, 1] [1, 2] (2 rows) works fine, but I can't seem to turn those values into actual ints or anything else for that matter, apart from text via the json_array_elements_text() function. => select n::integer[] from json_array_elements_text('[[0, 1], [1, 2]]') as x(n); ERROR: malformed array literal: "[0, 1]" DETAIL: Missing "]" after array dimensions. => select n::text[]::integer[] from json_array_elements_text('[[0, 1], [1, 2]]') as x(n); ERROR: malformed array literal: "[0, 1]" DETAIL: Missing "]" after array dimensions. Thoughts gratefully received; Rory -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general