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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-32) [hbase] Add row count estimator
Date Mon, 04 May 2009 17:34:30 GMT

    [ https://issues.apache.org/jira/browse/HBASE-32?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12705656#action_12705656
] 

stack commented on HBASE-32:
----------------------------

HFile does some of this already:

+ average key length
+ average value length
+ key count
+ entries in block and meta index
+ last key in file

These are easy to add if we need more.

Yeah, we should leverage it if only to read all meta in one region and then extrapolate (as
you suggest).

> [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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