pg_field_size() returns the internal storage size (in bytes) of the field number in the given PostgreSQL result. Field numbering starts at 0. A field size of -1 indicates a variable length field. This function will return FALSE on error.
See the example given at the pg_field_name() page.
Note: This function used to be called pg_fieldsize().
See also pg_field_prtlen() and pg_field_type().