Package org.apache.flink.table.runtime.operators.over.frame

Interface OverWindowFrame

All Superinterfaces:
Serializable
All Known Implementing Classes:
InsensitiveOverFrame, OffsetOverFrame, RangeSlidingOverFrame, RangeUnboundedFollowingOverFrame, RangeUnboundedPrecedingOverFrame, RowSlidingOverFrame, RowUnboundedFollowingOverFrame, RowUnboundedPrecedingOverFrame, SlidingOverFrame, UnboundedFollowingOverFrame, UnboundedOverWindowFrame, UnboundedPrecedingOverFrame
public interface OverWindowFrame extends Serializable
A window frame calculates the results for those records belong to a window frame. Before use a frame must be prepared by passing it all the records in the current partition. A frame is a subset of the current partition and the frame clause specifies how to define the subset. Frames are determined with respect to the current row, which enables a frame to move within a partition depending on the location of the current row within its partition. More information: https://docs.oracle.com/cd/E17952_01/mysql-8.0-en/window-functions-frames.html

E.g.: SELECT d, e, f, sum(e) over (partition by d order by e rows between 5 PRECEDING and 2 FOLLOWING), -- frame 1 count(*) over (partition by d order by e desc rows between 6 PRECEDING and 2 FOLLOWING), -- frame 2 max(f) over (partition by d order by e rows between UNBOUNDED PRECEDING and CURRENT ROW), -- frame 3 min(h) over (partition by d order by e desc rows between CURRENT ROW and UNBOUNDED FOLLOWING), -- frame 4 h FROM Table5 The above sql has 4 frames.

Over AGG means that every Row has a corresponding output. OverWindowFrame is called by: 1.Get all data and invoke prepare(ResettableExternalBuffer) for partition 2.Then each Row is traversed one by one to invoke process(int, RowData) to get the calculation results of the currentRow.