Tip:Arrays are not sets; searching for specific array elements can be a sign of database misdesign. Consider using a separate table with a row for each item that would be an array element. This will be easier to search, and is likely to scale better for a large number of elements.
Are arrays in PostgreSQL like associative arrays in Oracle PL/SQL hash tables?, that is an association between key & values? where the integer indexes stand in reality for keys?