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https://issues.apache.org/jira/browse/FLINK-5624?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15853718#comment-15853718
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Fabian Hueske commented on FLINK-5624:
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Hi [~wheat9], windowing is a way to define groups of records. It is used to
define {{GROUP BY}} and {{OVER}} aggregates. Both types of aggregates are
semantically different.
* {{GROUP BY}} aggregation: Groups multiple records and emits one row for the
whole group. The emitted row may only have fields which are identical in all
records of the group (grouping columns) or aggregated over all records of the
group.
* {{OVER}} aggregation: Emits one row for each input row, but the aggregate is
computed over multiple records which are defined by the {{OVER}} clause.
So, these are actually two different operators.
Regarding the built-in function. There is FLINK-5710 to define a {{procTime()}}
function which shall serve a similar purpose.
For now, adding a {{rowTime()}} function is fine, IMO. However, we need to
redesign this to support joins based on time which requires us to associate the
function with a table.
> Support tumbling window on streaming tables in the SQL API
> ----------------------------------------------------------
>
> Key: FLINK-5624
> URL: https://issues.apache.org/jira/browse/FLINK-5624
> Project: Flink
> Issue Type: Bug
> Components: Table API & SQL
> Reporter: Haohui Mai
> Assignee: Haohui Mai
>
> This is a follow up of FLINK-4691.
> FLINK-4691 adds supports for group-windows for streaming tables. This jira
> proposes to expose the functionality in the SQL layer via the {{GROUP BY}}
> clauses, as described in
> http://calcite.apache.org/docs/stream.html#tumbling-windows.
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