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https://issues.apache.org/jira/browse/CASSANDRA-4835?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jonathan Ellis reopened CASSANDRA-4835:
---------------------------------------

      Assignee: Sylvain Lebresne

Sylvain points out that we actually do expect update order to be preserved 
*within the same row*.  Reopening.
                
> Appending/Prepending items to list using BATCH
> ----------------------------------------------
>
>                 Key: CASSANDRA-4835
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4835
>             Project: Cassandra
>          Issue Type: Bug
>    Affects Versions: 1.2.0 beta 1
>            Reporter: Krzysztof Cieslinski
>            Assignee: Sylvain Lebresne
>            Priority: Minor
>
> As I know, there is no any guarantee that commands that are inside BATCH 
> block will execute in same order, as they are stored in the BATCH block. 
> But...
> I have made two tests:
> First appends some items to the empty list, and the second one, prepends 
> items, also to the empty list. Both of them are using UPDATE commands stored 
> in the BATCH block. 
> Results of those tests are as follow:
> First:
>       When appending new items to list, USING commands are executed in the 
> same order as they are stored i BATCH.
> Second:
>       When prepending new items to list, USING commands are executed in 
> random order.  
> So, in other words below code:
> {code:xml}
> BEGIN BATCH
>  UPDATE... list_name = list_name + [ '1' ]  
>  UPDATE... list_name = list_name + [ '2' ]
>  UPDATE... list_name = list_name + [ '3' ] 
> APPLY BATCH;{code}
>  always results in [ '1', '2', '3' ],
>  but this code:
> {code:xml}
> BEGIN BATCH
>  UPDATE... list_name = [ '1' ] + list_name   
>  UPDATE... list_name = [ '2' ] + list_name
>  UPDATE... list_name = [ '3' ] + list_name
> APPLY BATCH;{code}
> results in randomly ordered list, like [ '2', '1', '3' ]    (expected result 
> is [ '3', '2', '1' ])
> So somehow, when appending items to list, commands from BATCH are executed in 
> order as they are stored, but when prepending, the order is random.

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