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https://issues.apache.org/jira/browse/CASSANDRA-4835?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13481449#comment-13481449
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Jonathan Ellis commented on CASSANDRA-4835:
-------------------------------------------
You should consider this an implementation quirk (possibly even a bug), not a
guarantee.
> 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
> 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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