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https://issues.apache.org/jira/browse/CASSANDRA-5099?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13551185#comment-13551185
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Sylvain Lebresne commented on CASSANDRA-5099:
---------------------------------------------
bq. So, is the patch looking good?
Yes, +1. I've created CASSANDRA-5149 for the follow up.
> Since 1.1, get_count sometimes returns value smaller than actual column count
> -----------------------------------------------------------------------------
>
> Key: CASSANDRA-5099
> URL: https://issues.apache.org/jira/browse/CASSANDRA-5099
> Project: Cassandra
> Issue Type: Bug
> Affects Versions: 1.1.7
> Reporter: Jason Harvey
> Assignee: Yuki Morishita
> Fix For: 1.1.9
>
> Attachments: 5099-1.1.txt
>
>
> We have a CF where rows have thousands of TTLd columns. The columns are
> continually added at a regular rate, and TTL out after 15 minutes. We
> continually run a 'get_count' on these keys to get a count of the number of
> live columns.
> Since we upgrade from 1.0 to 1.1.7, "get_count" regularly returns much
> smaller values than are possible. For example, with roughly 15,000 columns
> that have well-distributed TTLs, running a get_count 10 times will result in
> 1 or 2 results that are up to half the actual column count. Using a normal
> 'get' to count those columns always results in proper values.
> For example:
> (all of these counts were ran within a second or less of eachother)
> {code}
> [default@reddit] count AccountsActiveBySR['2qh0u'];
> 13665 columns
> [default@reddit] count AccountsActiveBySR['2qh0u'];
> 13665 columns
> [default@reddit] count AccountsActiveBySR['2qh0u'];
> 13666 columns
> [default@reddit] count AccountsActiveBySR['2qh0u'];
> 3069 columns
> [default@reddit] count AccountsActiveBySR['2qh0u'];
> 13660 columns
> [default@reddit] count AccountsActiveBySR['2qh0u'];
> 13661 columns
> {code}
> I should note that this issue happens much more frequently with larger (>10k
> columns) rows than smaller rows. It never seems to happen with rows having
> fewer than 1k columns.
> There are no supercolumns in use. The key names and column names are very
> short, and there are no column values. The CF is LCS, and due to the TTL only
> hovers around a few MB in size. GC grace is normally at zero, but the problem
> is consistent with non-zero gc grace times.
> It appears that there was an issue (CASSANDRA-4833) fixed in 1.1.7 regarding
> get_count. Some logic was added to prevent an infinite loop case. Could that
> change have resulted in this problem somehow? I can't find any other relevant
> 1.1 changes that might explain this issue.
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