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Date: Wed, 2 Apr 2014 16:17:17 +0000 (UTC)
From: "Tyler Hobbs (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
Message-ID: <JIRA.12699517.1394229423861.51800.1396455437364@arcas>
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Subject: [jira] [Updated] (CASSANDRA-6825) Slice Queries Can Skip
 Intersecting SSTables
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     [ https://issues.apache.org/jira/browse/CASSANDRA-6825?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Tyler Hobbs updated CASSANDRA-6825:
-----------------------------------

    Attachment: 6825-2.0-v2.txt

bq. I think you meant something along the lines of a slice of say {{((1, 3), "")}} with min={{(0, 1)}} and max={{(3, 2)}}

Oops, you're correct there.

Your simplification is good, except that the equality check for the start and finish needs to happen after the min/max intersects check.  Non-equal start/finish can still fall outside the min/max range.

The v2 patch uses the simplification with that correction.  (The branch is also updated.)

> Slice Queries Can Skip Intersecting SSTables
> --------------------------------------------
>
>                 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
>             Fix For: 2.0.7, 2.1 beta2
>
>         Attachments: 6825-2.0-v2.txt, 6825-2.0.txt, 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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