Find all values of a partition column in Iceberg tables using the Java API

Question

I want to query an Iceberg table using the Java API directly (without Spark) to find all distinct values of a column which is used as partition column. What is the most efficient way, starting from a TableScan?

I can use an iterable like this, where table is the Table variable in question

CloseableIterable<Record> iterable = IcebergGenerics.read(table).project(table.spec().schema()).build();

but this is too inefficient.