[FLINK-5653] Add processing time OVER ROWS BETWEEN x PRECEDING aggregation to SQL

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Implemented
• Fix Version/s: 1.3.0
• Component/s: Table SQL / API
• Assignee: Stefano Bortoli
• Reporter: Fabian Hueske
• Created: 26/Jan/17 13:35
• Updated: 30/Mar/17 22:09
• Resolved: 30/Mar/17 22:09

Description

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

Queries similar to the following should be supported:

SELECT 
  a, 
  SUM(b) OVER (PARTITION BY c ORDER BY procTime() ROWS BETWEEN 2 PRECEDING AND CURRENT ROW) AS sumB,
  MIN(b) OVER (PARTITION BY c ORDER BY procTime() 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 PARTITION BY clause is optional (no partitioning results in single threaded execution).
• The ORDER BY clause may only have procTime() as parameter. procTime() is a parameterless scalar function that just indicates processing time mode.
• UNBOUNDED PRECEDING is not supported (see FLINK-5656)
• 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

• is required by: FLINK-4678 Add SessionRow row-windows to Table API
• is required by: FLINK-4679 Add TumbleRow row-windows to Table API
• is required by: FLINK-4680 Add SlidingRow row-windows to Table API
• links to: GitHub Pull Request #3443
• links to: GitHub Pull Request #3547
• links to: GitHub Pull Request #3574
• links to: GitHub Pull Request #3653