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Posted to issues@hbase.apache.org by "Josh Wymer (JIRA)" <ji...@apache.org> on 2012/08/03 01:25:02 UTC
[jira] [Created] (HBASE-6506) Setting CACHE_BLOCKS to false in an
hbase shell scan doesn't work
Josh Wymer created HBASE-6506:
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Summary: Setting CACHE_BLOCKS to false in an hbase shell scan doesn't work
Key: HBASE-6506
URL: https://issues.apache.org/jira/browse/HBASE-6506
Project: HBase
Issue Type: Bug
Components: shell
Affects Versions: 0.94.0
Reporter: Josh Wymer
Priority: Minor
I was attempting to prevent blocks from being cached by setting CACHE_BLOCKS => false in the hbase shell when doing a scan but I kept seeing tons of evictions when I ran it. After inspecting "table.rb" I found this line:
cache = args["CACHE_BLOCKS"] || true
The problem then is that if CACHE_BLOCKS is false then this expression will always return true. Therefore, it's impossible to turn off block caching.
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[jira] [Commented] (HBASE-6506) Setting CACHE_BLOCKS to false in an
hbase shell scan doesn't work
Posted by "stack (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/HBASE-6506?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13428866#comment-13428866 ]
stack commented on HBASE-6506:
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Can you make a patch Josh? Thanks.
You probably don't want to turn off caching completely? You should cache at least the blocks that hold the hfile indices. Otherwise, if caching fully off, any read will have to bring in the indices each time first.
> Setting CACHE_BLOCKS to false in an hbase shell scan doesn't work
> -----------------------------------------------------------------
>
> Key: HBASE-6506
> URL: https://issues.apache.org/jira/browse/HBASE-6506
> Project: HBase
> Issue Type: Bug
> Components: shell
> Affects Versions: 0.94.0
> Reporter: Josh Wymer
> Priority: Minor
> Labels: cache, ruby, scan, shell
> Original Estimate: 1m
> Remaining Estimate: 1m
>
> I was attempting to prevent blocks from being cached by setting CACHE_BLOCKS => false in the hbase shell when doing a scan but I kept seeing tons of evictions when I ran it. After inspecting "table.rb" I found this line:
> cache = args["CACHE_BLOCKS"] || true
> The problem then is that if CACHE_BLOCKS is false then this expression will always return true. Therefore, it's impossible to turn off block caching.
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[jira] [Commented] (HBASE-6506) Setting CACHE_BLOCKS to false in an
hbase shell scan doesn't work
Posted by "Zhihong Ted Yu (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/HBASE-6506?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13427730#comment-13427730 ]
Zhihong Ted Yu commented on HBASE-6506:
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Nice catch.
> Setting CACHE_BLOCKS to false in an hbase shell scan doesn't work
> -----------------------------------------------------------------
>
> Key: HBASE-6506
> URL: https://issues.apache.org/jira/browse/HBASE-6506
> Project: HBase
> Issue Type: Bug
> Components: shell
> Affects Versions: 0.94.0
> Reporter: Josh Wymer
> Priority: Minor
> Labels: cache, ruby, scan, shell
> Original Estimate: 1m
> Remaining Estimate: 1m
>
> I was attempting to prevent blocks from being cached by setting CACHE_BLOCKS => false in the hbase shell when doing a scan but I kept seeing tons of evictions when I ran it. After inspecting "table.rb" I found this line:
> cache = args["CACHE_BLOCKS"] || true
> The problem then is that if CACHE_BLOCKS is false then this expression will always return true. Therefore, it's impossible to turn off block caching.
--
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