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https://issues.apache.org/jira/browse/PHOENIX-4845?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16654364#comment-16654364
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Lars Hofhansl commented on PHOENIX-4845:
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Some comments:
# This is allows Phoenix to directly have the equivalent of HBase's
Scan.setStartRow, which can be pretty powerful.
# Perhaps we should call this WITH STARTROW (instead of OFFSET)
# That said. An HBase SEEK seeks to a certain place and next() would return the
next row. If the SEEK hit a row directly it would return that very row. Hence
perhaps we'd need an EXCLUSIVE options. I.e. WITH STARTROW EXCLUSIVE?
# What if we also have a WHERE clause? I suppose in that case we should not try
to optimize that. Use WITH STARTROW to set the start-row and the WHERE clause
is just a filter (at most a SKIP SCAN).
The details are tricky. :)
> 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]
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