support window functions #1112
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support window functions #1112
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Which issue does this PR close?
Closes #542 .
Rationale for this change
As stated in #542, datafusion adds
SortExecandRepartitionExecbased on the window clausespartition byandorder by(Seeenforce_distribution.rsin datafusion andWindowAggExec::required_input_distribution.From what I can see, this restriction on window functions in ballista was put way back when datafusion was in the same repo as ballista and window function support was still in its infancy. Now that datafusion enforces the right hash distribution by placing repartition nodes, I believe ballista currently already supports window functions.
I have tested partitioned, unpartitioned and sorted window expressions with ballista with this PR and compared them with datafusion, it seems to be working as intended. Parititioned window functions get repartitioned by their partition expressions and are parallelised.
Not sure what is the best way to test this given distribution handling is done by datafusion here.
What changes are included in this PR?
Allow queries with window expressions
Are there any user-facing changes?