Hello
I looked on some constructs that helps with iteration over array in
plpgsql. I propose a following syntax:
FOR var IN [array variable | array expression]
LOOP
..
END LOOP
var - declared variable - theoretically we can a detect var type from
array type, but it needs a early expression an analyze (not used in
PL/pgSQL), so var should be declared before. This construct ensure
iteration over all items of array. When somebody needs a subscripts
from some dimension, then he can use a proposed function "subscripts".
so iteration over two dimensional array can be written:
DECLARE
i integer;
j integer;
BEGIN
FOR i IN subscripts(myarray, 1) LOOP
FOR j IN subscripts(myarray, 2) LOOP
RAISE NOTICE 'myarray[%,%] = %', i, j, myarray[i,j];
END LOOP;
END LOOP;
When input array is multidimensional, then this array is flattened -
order of iteration is specified by physical store of items inside the
array. This construct iterate over all items of input array - it has a
same behave as "unnest" function.
some examples:
DECLARE
v integer;
a int[] := ARRAY[2,3.4,5];
BEGIN
FOR val IN a
LOOP
RAISE NOTICE '%', val; -- produce 2,3,4,5
END LOOP;
FOR val IN subscripts(a, 1)
LOOP
RAISE NOTICE '%', val; -- produce 1,2,3,4
END LOOP;
FOR val IN subscripts(a,1)
LOOP
RAISE NOTICE '%', a[val]; -- produce 2,3,4,5
END LOOP;
END;
Comments, ideas?
Regards
Pavel Stehule
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