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From "Jonathan Gray (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-32) [hbase] Add row count estimator
Date Mon, 04 May 2009 16:17:30 GMT

    [ https://issues.apache.org/jira/browse/HBASE-32?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12705639#action_12705639

Jonathan Gray commented on HBASE-32:

I think we should be storing statistics about StoreFiles in the new HFile meta blocks.  To
start, this could be things like total row count in the storefile.  Eventually could expand
that in to a row index.

These kinds of statistics could be useful all over the place.

> [hbase] Add row count estimator
> -------------------------------
>                 Key: HBASE-32
>                 URL: https://issues.apache.org/jira/browse/HBASE-32
>             Project: Hadoop HBase
>          Issue Type: New Feature
>          Components: client
>            Reporter: stack
>            Priority: Minor
>         Attachments: 2291_v01.patch, Keying.java
> Internally we have a little tool that will do a rough estimate of how many rows there
are in a dataHbase.  It keeps getting larger and larger partitions running scanners until
it turns up > N occupied rows.  Once it has a number > N, it multiples by the partition
size to get an approximate row count.  
> This issue is about generalizing this feature so it could sit in the general hbase install.
 It would look something like:
> {code}
> long getApproximateRowCount(final Text startRow, final Text endRow, final long minimumCountPerPartition,
final long maximumPartitionSize)
> {code}
> Larger minimumCountPerPartition and maximumPartitionSize values would make the count
more accurate but would mean the method ran longer.

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