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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-2722) support mysql "limit,offset" clauses
Date Mon, 04 Apr 2016 23:40:25 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-2722?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15225285#comment-15225285
] 

ASF GitHub Bot commented on PHOENIX-2722:
-----------------------------------------

Github user JamesRTaylor commented on a diff in the pull request:

    https://github.com/apache/phoenix/pull/154#discussion_r58467402
  
    --- Diff: phoenix-core/src/main/java/org/apache/phoenix/coprocessor/ScanRegionObserver.java
---
    @@ -218,7 +228,11 @@ protected RegionScanner doPostScannerOpen(final ObserverContext<RegionCoprocesso
             if (j != null) {
                 innerScanner = new HashJoinRegionScanner(innerScanner, p, j, tenantId, c.getEnvironment());
             }
    -
    +        if (scanOffset != null) {
    +            innerScanner = getOffsetScanner(c, innerScanner,
    +                    new OffsetResultIterator(new RegionScannerResultIterator(innerScanner),
scanOffset),
    +                    scan.getAttribute(QueryConstants.LAST_SCAN) == null ? false : true);
    --- End diff --
    
    Nit: change this:
    
        scan.getAttribute(QueryConstants.LAST_SCAN) == null ? false : true
    
    to this:
    
        scan.getAttribute(QueryConstants.LAST_SCAN) != null


> support mysql "limit,offset" clauses 
> -------------------------------------
>
>                 Key: PHOENIX-2722
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-2722
>             Project: Phoenix
>          Issue Type: New Feature
>            Reporter: Ankit Singhal
>            Assignee: Ankit Singhal
>            Priority: Minor
>         Attachments: PHOENIX-2722.patch, PHOENIX-2722_formatted.patch
>
>
> For serial query(query with “serial" hint or  “limit" without "order by”), we can
limit each scan(using page filter) to “limit+offset” instead of limit earlier.
> And then, for all queries, we can forward the relevant client iterators to the offset
provided and then return the result.
> syntax
> {code}
> [ LIMIT { count } ]
>     [ OFFSET start [ ROW | ROWS ] ]
>     [ FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ONLY ]
> {code}
> Some new keywords(OFFSET,FETCH,ROW, ROWS,ONLY) are getting introduced so users might
need to see that they are not using them as column name or something.
> WDYT, [~jamestaylor]



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