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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-867) If millions of columns in a column family, hbase scanner won't come up
Date Fri, 20 Feb 2009 01:26:02 GMT

    [ https://issues.apache.org/jira/browse/HBASE-867?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12675207#action_12675207
] 

stack commented on HBASE-867:
-----------------------------

>From #IRC, here is another case we need to be smarter about:

{code}
01:13 < BenM>       keys[i] = new HStoreKey(HConstants.EMPTY_BYTE_ARRAY, this.store.getHRegionInfo());
01:13 < BenM>       if (firstRow != null && firstRow.length != 0) {
01:13 < BenM>         if (findFirstRow(i, firstRow)) {
01:13 < BenM>           continue;
01:13 < BenM>         }
01:13 < BenM>       }
01:13 < BenM>       while (getNext(i)) {
01:13 < BenM>         if (columnMatch(i)) {
01:13 < BenM>           break;
01:13 < BenM>         }
01:13 < BenM>       }
{code}

Its setting up scanners after store files have been changed.

If lots of entries for rows we don't care about, then these iterations will take a long time.
 Need to be smarter about the seek.

> If millions of columns in a column family, hbase scanner won't come up
> ----------------------------------------------------------------------
>
>                 Key: HBASE-867
>                 URL: https://issues.apache.org/jira/browse/HBASE-867
>             Project: Hadoop HBase
>          Issue Type: Bug
>            Reporter: stack
>            Assignee: stack
>            Priority: Critical
>             Fix For: 0.20.0
>
>
> Our Daniel has uploaded a table that has a column family with millions of columns in
it.  He can get items from the table promptly specifying row and column.  Scanning is another
matter.  Thread dumping I see we're stuck in the scanner constructor nexting through cells.

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