[FLINK-6145] Add [non-partitioned] event time OVER ROWS BETWEEN x PRECEDING aggregation to SQL

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Component/s: Table SQL / API
• Assignee: sunjincheng
• Reporter: sunjincheng
• Created: 21/Mar/17 16:09
• Updated: 25/Mar/17 00:33
• Resolved: 24/Mar/17 19:34

Description

The goal of this issue is to add support for OVER ROWS aggregations on event time streams to the SQL interface.

Queries similar to the following should be supported:

SELECT 
  a, 
  SUM(b) OVER (ORDER BY rowTime() ROWS BETWEEN 2 PRECEDING AND CURRENT ROW) AS sumB,
  MIN(b) OVER (ORDER BY rowTime() ROWS BETWEEN 2 PRECEDING AND CURRENT ROW) AS minB
FROM myStream

The following restrictions should initially apply:

• All OVER clauses in the same SELECT clause must be exactly the same.
• The ORDER BY clause may only have rowTime() as parameter. rowTime() is a parameterless scalar function that just indicates event time mode.
• UNBOUNDED PRECEDING is not supported (see FLINK-5804)
• FOLLOWING is not supported.

The restrictions will be resolved in follow up issues. If we find that some of the restrictions are trivial to address, we can add the functionality in this issue as well.

This issue includes:

• Design of the DataStream operator to compute OVER ROW aggregates
• Translation from Calcite's RelNode representation (LogicalProject with RexOver expression).

Issue Links

• links to: GitHub Pull Request #3585