[FLINK-21863] SortPartition should allow chaining of KeySelectors to support different sorting orders for the fields

• Type: Improvement
• Status: Open
• Priority: Not a Priority
• Resolution: Unresolved
• Component/s: API / DataSet
• Labels: auto-deprioritized-major auto-deprioritized-minor
• Assignee: Unassigned
• Reporter: Etienne Chauchot
• Created: 18/Mar/21 15:19
• Updated: 03/Dec/21 22:38

Description

If we need to sort data in a DataSet using a KeySelector (for example to extract avro fields or when sort using field index or name is not available) we cannot have different sort orders for the fields. We can sort by a list of fields by making the keySelector return a tuple but they will all be sorted in the same order.
To allow sort by field 1 ASC, field 2 DESC kind of semantics with KeySelectors we need to be able to chain the KeySelectors like this

DataSet.sortPartition(field1KeySelector , Order.ASCENDING)
                .sortPartition(field2KeySelector, Order.DESCENDING)

which is currently not possible.