[jira] [Commented] (HBASE-11541) Wrong result when scaning meta with startRow

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

    [ https://issues.apache.org/jira/browse/HBASE-11541?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14066523#comment-14066523 ] 

stack commented on HBASE-11541:
-------------------------------

Hmm.  I thought we were past all issues w/ our meta compare.  Thanks for noticing and fixing this one.  The patch looks good to me because it looks like how I thought this worked (smile).  I will wait on hadoopqa.  (I wonder if this compare was changed in the past?)  The tests are very nice.

> Wrong result when scaning meta with startRow
> --------------------------------------------
>
>                 Key: HBASE-11541
>                 URL: https://issues.apache.org/jira/browse/HBASE-11541
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Liu Shaohui
>            Assignee: Liu Shaohui
>            Priority: Minor
>         Attachments: HBASE-11541-trunk-v1.diff
>
>
> When we scan the meta with STARTROW optiion, wrong result may be returned.
> For exmaple: if there are two tables named "a" and "b" in hbase, when we scan the meta with startrow = 'b', the region location of table "a" will be returned but we expect to get the region location of table "b".
>  {code}
> > create 'a', {NAME => 'f'}
> > create 'b', {NAME => 'f'}
> > scan '.META.', {STARTROW => 'b', LIMIT => 1}
> a,,1405655897758.f8b547476b6dc80545e6413c31396, xxxx
> {code}
> The reason is the wrong assumption in MetaKeyComparator
> See: KeyValue.java#2011
> {code}
>       int leftDelimiter = getDelimiter(left, loffset, llength,
>           HRegionInfo.DELIMITER);
>       int rightDelimiter = getDelimiter(right, roffset, rlength,
>           HRegionInfo.DELIMITER);
>       if (leftDelimiter < 0 && rightDelimiter >= 0) {
>         // Nothing between .META. and regionid.  Its first key. 
>         return -1;
>       } else if (rightDelimiter < 0 && leftDelimiter >= 0) {
>         return 1;
>       } else if (leftDelimiter < 0 && rightDelimiter < 0) {
>         return 0;
>       }
> {code}
> It's a little troublesome to fix this problem for given a start row which contains more than two "," for meta, it's not easy to extract the startKey of region.
> eg: STARTROW => 'aaa,bbb,ccc,xxx'.
> Comments and suggestions are welcomed. Thanks



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