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From "Tyler Hobbs (JIRA)" <>
Subject [jira] [Updated] (CASSANDRA-6825) Slice Queries Can Skip Intersecting SSTables
Date Wed, 02 Apr 2014 16:17:17 GMT


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:
>             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,,
> 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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