Re: Looking for a way to sum integer arrays.... - Mailing list pgsql-sql

You would definitely want to look into using pl/R for this.  Also, other 
procedure languages (perl, for example) work well with arrays so may be 
easier to use for this situation.  As for the aggregate, I don't know how to 
make that more dynamic in terms of return value.

Sean

----- Original Message ----- 
From: "Tony Wasson" <ajwasson@gmail.com>
To: <pgsql-sql@postgresql.org>
Sent: Thursday, April 21, 2005 9:21 PM
Subject: [SQL] Looking for a way to sum integer arrays....


I'd like to be able to sum up an integer array. Like so:
     {3,2,1}  + {0,2,2}      -------     {3,4,3}

The following solution I've been hacking on works, although I think it
is far from "ideal". Is there a built in way to sum up arrays? If not,
is there a better way than my crude method? I have tested this on 7.4
and 8.0. I'd also be appreciate if any insight on why my aggregate
fails to work when I have an empty initcondition.  P.S. I have never
written an aggregate and I was lost trying to follow the complex_sum
example in the docs.
---------------------------------------------
CREATE OR REPLACE FUNCTION sum_intarray(INTEGER[],INTEGER[]) RETURNS
INTEGER[] LANGUAGE 'plpgsql' AS '
/*
|| Author: Tony Wasson
||
|| Overview: Experiment with arrays and aggregates
||      3,2,1
||    + 0,2,2
||     -------
||      3,4,3
||
|| Revisions: (when, who, what)
||  2005/04/21 -- TW - Create function
*/
DECLARE   inta1   ALIAS FOR $1;   inta2   ALIAS FOR $2;   out_arr     INTEGER[];   out_arr_text    TEXT := '''';   i
      INTEGER;   nextnum     INTEGER;
 
BEGIN   FOR i IN array_lower(inta1, 1)..array_upper(inta1, 1)   LOOP       RAISE NOTICE ''looking at element %'',i;
 nextnum := COALESCE(inta1[i],0) + COALESCE(inta2[i],0);       RAISE NOTICE ''nextnum %'',nextnum;       out_arr_text
:=out_arr_text || nextnum::TEXT || '','';       RAISE NOTICE ''text %'',out_arr_text;   END LOOP;   RAISE NOTICE ''text
%'',out_arr_text;  --drop the last comma   IF SUBSTRING(out_arr_text,length(out_arr_text),1) =  '','' THEN
out_arr_text:= substring(out_arr_text,1,length(out_arr_text)-1);   END IF;   out_arr_text := ''{'' || out_arr_text ||
''}'';  RAISE NOTICE ''text %'',out_arr_text;   out_arr := out_arr_text;   RAISE NOTICE ''out_arr %'',out_arr;
 
RETURN out_arr;
END
';

SELECT sum_intarray('{1,2}','{2,3}');
SELECT sum_intarray('{3,2,1}','{0,2,2}');

--- Now I make a table to demonstrate an aggregate on

CREATE TABLE arraytest (   id character varying(10) NOT NULL,   somearr integer[]
);

INSERT INTO arraytest (id, somearr) VALUES ('a', '{1,2,3}');
INSERT INTO arraytest (id, somearr) VALUES ('b', '{0,1,2}');


CREATE AGGREGATE sum_integer_array (   sfunc = sum_intarray,   basetype = INTEGER[],   stype = INTEGER[],   initcond =

'{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}'
);

----------------------

# SELECT sum_integer_array(somearr) FROM arraytest;                            sum_integer_array

---------------------------------------------------------------------------------{1,3,5,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}Thanks
inadvance to anyone who reads this far.Tony Wassonajwasson@gmail.com---------------------------(end of
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