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https://issues.apache.org/jira/browse/SPARK-28648?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17238654#comment-17238654
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jiaan.geng commented on SPARK-28648:
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it seems groups only exists in PgSQL
> Adds support to `groups` unit type in window clauses
> ----------------------------------------------------
>
> Key: SPARK-28648
> URL: https://issues.apache.org/jira/browse/SPARK-28648
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Affects Versions: 3.0.0
> Reporter: Dylan Guedes
> Priority: Major
>
> Spark currently support the two most common window functions unit types: rows
> and ranges. However, in PgSQL a new type was added: `groups`.
> According to [this
> source|https://blog.jooq.org/2018/07/05/postgresql-11s-support-for-sql-standard-groups-and-exclude-window-function-clauses/],
> the difference is:
> """ROWS counts the exact number of rows in the frame.
> RANGE performs logical windowing where we don’t count the number of rows, but
> look for a value offset.
> GROUPS counts all groups of tied rows within the window."""
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