Execution of a comparison UDR for sort
When you create opaque data types, you create the support
function compare() to sort the UDT data during
ORDER BY, UNIQUE, DISTINCT, and UNION clauses and CREATE INDEX operations.
SELECT udtcol FROM t ORDER BY 1;If the udtcol column has a comparison UDR that is parallelizable and the client enables parallel sort, each sort thread participating in the parallel sort for the order by clause executes the comparison UDR in parallel.