PL/pgSQL multidimension (matrix) array in function

I found how to use, inside a PL/pgSQL function, a two-dimensions array (matrix).
There is a limitation: the number of the 'columns' of the matrix is fixed at
declaration time (in DECLARE section) and you need to manually initialize all
the elements in the first 'row' of the matrix.

The number of rows is unlimited and can be sized at runtime.

Here is the code that can help you.

If someone know how to manage an NxN array without limitations, please replay
to this thread.

I'm using PostgreSQL 7.4.1 on RH7.3

Cheers
Sergio

CREATE OR REPLACE FUNCTION "testarray" (integer) RETURNS SETOF integer AS'
DECLARE
n alias for $1; -- number of rows is passed as argument
i INTEGER;
j integer;
k INTEGER := 3; -- matrix columns number
b integer[] := array[0,0,0]; -- need it to initialize the matrix!!
a integer[][] := array[[0,0,0]]; -- need it to initialize the matrix!!
begin

for i in 1..n loop -- the i loop can start obviously from 2 (the first
row is already present...) but for our purpose here we use 1
a := array_cat(a,b);
for j in 1..k loop
a[i][j] := i*j;
end loop;
end loop;
for i in 1..n loop

return next null;
return next i; -- need it to format in some way the output :)
return next null;

for j in 1..k loop
return next a[i][j];
end loop;

end loop;
return;
end
'LANGUAGE 'plpgsql';


here is the output:

=> select * from testarray(8);
testarray
-----------

1

1
2
3

2

2
4
6

3

3
6
9

4

4
8
12

5

5
10
15

6

6
12
18

7

7
14
21

8

8
16
24
(48 rows)


--
------------------------------------------------------------ ---------
Sergio Fantinel EGEE Project
------------------------------------------------------------ ---------
INFN - Lab. Naz. di Legnaro phone: +39 049 8068 489
viale dell'Università n. 2,
35020 Legnaro (PD) ITALY sergio.fantinel@lnl.infn.it
------------------------------------------------------------ ---------

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Re: PL/pgSQL multidimension (matrix) array in function

Sergio Fantinel wrote:
> I found how to use, inside a PL/pgSQL function, a two-dimensions array
> (matrix).
> There is a limitation: the number of the 'columns' of the matrix is
> fixed at declaration time (in DECLARE section) and you need to manually
> initialize all the elements in the first 'row' of the matrix.

You should use '{}' to initialize the array to empty. See below for an
example:

CREATE OR REPLACE FUNCTION testarray (integer, integer) RETURNS SETOF
integer[] AS'
DECLARE
n alias for $1; -- number of rows is passed as argument
i INTEGER;
j integer;
k alias for $2; -- matrix columns number
a integer[];
begin
for i in 1..n loop
a := ''{}''; -- create empty array
for j in 1..k loop
a := a || i;
return next a;
end loop;
end loop;
return;
end;
'LANGUAGE 'plpgsql';

regression=# select * from testarray(2,3);
testarray
-----------
{1}
{1,1}
{1,1,1}
{2}
{2,2}
{2,2,2}
(6 rows)

HTH,

Joe

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