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Date: Tue, 10 Apr 2012 22:36:25 -0400
From: Josh Elser <josh.elser@gmail.com>
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To: user@accumulo.apache.org
Subject: Re: Using maxVersions=7 but rows disappear
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David,

I'd venture a guess that because you only set the scan maxVersions, when 
Accumulo minor compacted your 'rolling' table to flush those K/V pairs 
to disk, it deleted your first 6 versions that you saw when performing 
the scan.

You can determine if this is actually what happened by running your 
inserts below, and calling 'compact' on the table before performing the 
scan.

To fix this, try setting the same option with the minc and majc scope. 
Most likely (but don't quote me):

config -t rolling -s table.iterator.minc.vers.opt.maxVersions=7
config -t rolling -s table.iterator.majc.vers.opt.maxVersions=7

- Josh

On 4/10/2012 10:16 PM, David Medinets wrote:
> I'm still thinking about how to use accumulo to calculate weekly
> moving averages. I thought that using the maxVersions settings might
> work to maintain the last 7 values. Then a program could simply sum
> the values of a given row. So this is what I did:
>
> bin/accumulo shell -u root -p password
>> createtable rolling
> rolling>  config -t rolling -s table.iterator.scan.vers.opt.maxVersions=7
> rolling>  insert row cf cq 1
> rolling>  insert row cf cq 2
> rolling>  insert row cf cq 3
> rolling>  insert row cf cq 4
> rolling>  insert row cf cq 5
> rolling>  insert row cf cq 6
> rolling>  insert row cf cq 7
> rolling>  insert row cf cq 8
> rolling>  scan
> row cf:cq []    8
> row cf:cq []    7
> row cf:cq []    6
> row cf:cq []    5
> row cf:cq []    4
> row cf:cq []    3
> row cf:cq []    2
>
> This is exactly what I wanted to see. So I wrote a simple scanner
> program to read the table. Then I did another scan:
>
> rolling>  scan
> row cf:cq []    8
>
> Where did the rest of the records go?