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