[jira] [Commented] (PHOENIX-4845) Support using Row Value Constructors in OFFSET clause to support paging in tables where the sort order of PK columns varies

["Lars Hofhansl (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/PHOENIX-4845?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16652224#comment-16652224 ] 

Lars Hofhansl commented on PHOENIX-4845:
----------------------------------------

I like this. Can also be use when scanning along an index. If Phoenix can correctly optimize the ORDER BY away then we can force a start key as start point for the next page.

> Support using Row Value Constructors in OFFSET clause to support paging in tables where the sort order of PK columns varies
> ---------------------------------------------------------------------------------------------------------------------------
>
>                 Key: PHOENIX-4845
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-4845
>             Project: Phoenix
>          Issue Type: New Feature
>            Reporter: Thomas D'Silva
>            Priority: Major
>              Labels: DESC, SFDC
>
> RVCs along with the LIMIT clause are useful for efficiently paging through rows (see [http://phoenix.apache.org/paged.html]). 
>  However if the sorder order of the PK columns in a table varies we cannot use RVCs. 
> For eg. if the PK of a table is (A  DESC, B) we cannot use the following query to page through the data
> {code:java}
> SELECT * FROM TABLE WHERE (A, B) > (?, ?) ORDER BY A DESC, B LIMIT 20
> {code}
> Since the rows are sorted by A desc and then by B descending we need change the comparison order
> {code:java}
> SELECT * FROM TABLE WHERE (A, B) < (?, ?) ORDER BY A DESC, B LIMIT 20
> {code}
> If we supported using RVCs in the offset clause we could use the offset to set the start row of the scan. Clients would not have to have logic to determine the comparison operator.
> {code:java}
> SELECT * FROM TABLE ORDER BY A DESC, B LIMIT 20 OFFSET (?,?)
> {code}
> We would only allow using the offset if the rows are ordered by the sort order of the PK columns.
>  
> FYI [~jfernando_sfdc]



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