[jira] [Comment Edited] (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=16652639#comment-16652639 ] 

Lars Hofhansl edited comment on PHOENIX-4845 at 10/16/18 11:44 PM:
-------------------------------------------------------------------

Tried just how the parser changes would look like... It's not too bad.

Remaining changes are in QueryCompiler.compileSingleFlatQuery(...) and in OffsetCompiler.



was (Author: lhofhansl):
Tried just how the parser changes would look like... It's not too bad.

> 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
>         Attachments: PHOENIX-offset.txt
>
>
> RVCs along with the LIMIT clause are useful for efficiently paging through rows (see [http://phoenix.apache.org/paged.html]). This works well if the pk columns are sorted ascending, we can always use the > operator to query for the next batch of row. 
> However if the PK of a table is (A  DESC, B DESC) we cannot use the following query to page through the data
> {code:java}
> SELECT * FROM TABLE WHERE (A, B) > (?, ?) ORDER BY A DESC, B DESC 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 DESC LIMIT 20
> {code}
> If the PK of a table contains columns with mixed sort order for eg (A  DESC, B) then we cannot use RVC to page through data. 
> 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. This would also support paging through data for tables where the PK columns are sorted in mixed order. 
> {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]



--
This message was sent by Atlassian JIRA
(v7.6.3#76005)