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https://issues.apache.org/jira/browse/HBASE-14978?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Elliott Clark updated HBASE-14978:
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Description:
Scans and Multi's have limits on the total size of cells that can be returned.
However if those requests are not all pointing at the same blocks then the
KeyValues can keep alive a lot more data than their size.
Take the following example:
A multi with a list of 10000 gets to a fat row. Each column being returned in
in a different block. Each column is small 32 bytes or so.
So the total cell size will be 32 * 10000 = ~320kb. However if each block is
128k then total retained heap size will be almost 2gigs.
was:
Scans and Multi's have limits on the total size of cells that can be returned.
However if those requests are not all pointing at the same blocks then the
KeyValues can keep alive a lot more data than their size.
Take the following example:
A multi with a list of 10000 gets to a fat row. Each column being returned in
in a different block. Each column is small 32 bytes or so.
So the total cell size will be 32 * 10000 = ~320kb. However if each block is
128k then total retained heap size will be almost 40gigs.
> Don't allow Scans and Multi to retain too many blocks
> -----------------------------------------------------
>
> Key: HBASE-14978
> URL: https://issues.apache.org/jira/browse/HBASE-14978
> Project: HBase
> Issue Type: Improvement
> Affects Versions: 2.0.0, 1.2.0, 1.3.0
> Reporter: Elliott Clark
> Assignee: Elliott Clark
> Priority: Critical
>
> Scans and Multi's have limits on the total size of cells that can be
> returned. However if those requests are not all pointing at the same blocks
> then the KeyValues can keep alive a lot more data than their size.
> Take the following example:
> A multi with a list of 10000 gets to a fat row. Each column being returned in
> in a different block. Each column is small 32 bytes or so.
> So the total cell size will be 32 * 10000 = ~320kb. However if each block is
> 128k then total retained heap size will be almost 2gigs.
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