How to split an array into columns

["a" <372660931@xxxxxx>]

Say if I have an float8 array:

id| data

--|---------------

a | {1,2}

b | {2,4}

If I could using query to make it looks like this:

id| data[1] | data[2]

--|----------|-----------

a |      1      |     2

b |      2      |     4

Since I would have around 200,000 rows, I would prefer it having enough capacity to carry out the calculation such as sum().

Thank you so much!