Message-ID: <000c01c547fc$cf93fc80$5179f345@WATSON>
From: "Sean Davis" <sdavis2@mail.nih.gov>
To: "Tony Wasson" <ajwasson@gmail.com>, <pgsql-sql@postgresql.org>
References: <6d8daee30504211821515e7f11@mail.gmail.com>
Subject: Re: Looking for a way to sum integer arrays....
Date: Sat, 23 Apr 2005 08:05:58 -0400
MIME-Version: 1.0
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
	reply-type=original
Content-Transfer-Encoding: 7bit

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 in advance to anyone who reads this far.Tony Wassonajwasson@gmail.com---------------------------(end of broadcast)---------------------------TIP 3: if posting/reading through Usenet, please send an appropriate      subscribe-nomail command to majordomo@postgresql.org so that your      message can get through to the mailing list cleanly