Dandandan commented on a change in pull request #334:
URL: https://github.com/apache/arrow-datafusion/pull/334#discussion_r635518750
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File path: ballista/rust/core/proto/ballista.proto
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@@ -151,6 +153,25 @@ message AggregateExprNode {
LogicalExprNode expr = 2;
}
+enum BuiltInWindowFunction {
+ ROW_NUMBER = 0;
+ RANK = 1;
+ DENSE_RANK = 2;
+ LAG = 3;
+ LEAD = 4;
+ FIRST_VALUE = 5;
+ LAST_VALUE = 6;
+}
+
+message WindowExprNode {
+ oneof window_function {
+ AggregateFunction aggr_function = 1;
Review comment:
I checked whether this makes sense to reuse aggregate functions for
window expressions - I think it does! E.g. PostgreSQL also says:
https://www.postgresql.org/docs/9.3/functions-window.html
> In addition to these functions, any built-in or user-defined aggregate
function can be used as a window function (see Section 9.20 for a list of the
built-in aggregates). Aggregate functions act as window functions only when an
OVER clause follows the call; otherwise they act as regular aggregates.
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