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https://issues.apache.org/jira/browse/CASSANDRA-6825?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13951437#comment-13951437
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Tyler Hobbs commented on CASSANDRA-6825:
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It loos like CASSANDRA-6327 is the cause for this. The logic for testing
sstables for inclusion when there's a composite comparator and multiple
components in the slice filter is off. This showed up for {{count(\*)}}
because counting queries are always paged internally; the second page was
erroneously skipping an sstable. If the {{select *}} query has the same page
size (10k), it will also omit results.
> COUNT(*) with WHERE not finding all the matching rows
> -----------------------------------------------------
>
> Key: CASSANDRA-6825
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6825
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Environment: quad core Windows7 x64, single node cluster
> Cassandra 2.0.5
> Reporter: Bill Mitchell
> Assignee: Tyler Hobbs
> Attachments: cassandra.log, selectpartitions.zip,
> selectrowcounts.txt, testdb_1395372407904.zip, testdb_1395372407904.zip
>
>
> Investigating another problem, I needed to do COUNT(*) on the several
> partitions of a table immediately after a test case ran, and I discovered
> that count(*) on the full table and on each of the partitions returned
> different counts.
> In particular case, SELECT COUNT(*) FROM sr LIMIT 1000000; returned the
> expected count from the test 99999 rows. The composite primary key splits
> the logical row into six distinct partitions, and when I issue a query asking
> for the total across all six partitions, the returned result is only 83999.
> Drilling down, I find that SELECT * from sr WHERE s = 5 AND l = 11 AND
> partition = 0; returns 30,000 rows, but a SELECT COUNT(*) with the identical
> WHERE predicate reports only 14,000.
> This is failing immediately after running a single small test, such that
> there are only two SSTables, sr-jb-1 and sr-jb-2. Compaction never needed to
> run.
> In selectrowcounts.txt is a copy of the cqlsh output showing the incorrect
> count(*) results.
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