[GitHub] flink issue #4183: [FLINK-6969][table]Add support for deferred computation f...

[fhueske <gi...@git.apache.org>]

Github user fhueske commented on the issue:

    https://github.com/apache/flink/pull/4183
  
    Thanks for your thoughts @sunjincheng121 and @wuchong.
    I thought about this again and agree with you. We should have a separate parameters to specify watermark adjustments and early firings.
    
    I propose the following:
    
    1. We add a parameter `lateDataTimeOffset` which adjusts the watermarks at the source (actually at all sources of a query) by injecting a custom operator. The parameter can be positive or negative and adjusts the watermarks. I think the name is good because the watermarks control the lateness of records. Also, Table API / SQL users should not need to know about the concept of watermarks. **This is done as part of this issue / PR.**
    
    2. We add a parameter `earlyResultTimeOffset` which defines the time when the first early result (e.g., of a windowed aggregate) is computed. The parameter should be negative, i.e., a value of `-30.mins` results in early results which start 30 minute before the watermark reaches the end of a window. 
    
    3. The same `updateRate` parameter as in [FLINK-6649](https://issues.apache.org/jira/browse/FLINK-6649) / PR #4157 is used to control how often early results are updated. I don't think we need a special parameters for early result or late data updates.
    
    **2. and 3. are addressed in a separate issue.**
    
    What do you think?


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