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https://issues.apache.org/jira/browse/CASSANDRA-12867?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15630442#comment-15630442
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Nate McCall commented on CASSANDRA-12867:
-----------------------------------------
bq. but a more meaningful example triggering this could be:
[~slebresne] This is a common pattern to work around issues with the older
Java-Drivers setting null on prepared statements with values not defined
because at the app-level, you can check a value for null before adding the one
column insert into the batch knowing the will get merged server-side.
> Batch with multiple conditional updates for the same partition causes
> AssertionError
> ------------------------------------------------------------------------------------
>
> Key: CASSANDRA-12867
> URL: https://issues.apache.org/jira/browse/CASSANDRA-12867
> Project: Cassandra
> Issue Type: Bug
> Components: CQL
> Reporter: Kurt Greaves
> Assignee: Sylvain Lebresne
> Attachments: 12867-3.0.patch
>
>
> Reproduced in 3.0.10 and 3.10. Used to work in 3.0.9 and earlier. Bug was
> introduced in CASSANDRA-12060.
> The following causes an AssertionError:
> {code}
> CREATE KEYSPACE test WITH replication = { 'class' : 'SimpleStrategy',
> 'replication_factor' : 1 };
> create table test.test (id int PRIMARY KEY, val text);
> BEGIN BATCH INSERT INTO test.test (id, val) VALUES (999, 'aaa') IF NOT
> EXISTS; INSERT INTO test.test (id, val) VALUES (999, 'ccc') IF NOT EXISTS;
> APPLY BATCH ;
> {code}
> Stack trace is as follows:
> {code}
> ERROR [Native-Transport-Requests-2] 2016-10-31 04:16:44,231 Message.java:622
> - Unexpected exception during request; channel = [id: 0x176e1c04,
> L:/127.0.0.1:9042 - R:/127.0.0.1:59743]
> java.lang.AssertionError: null
> at
> org.apache.cassandra.cql3.statements.CQL3CasRequest.setConditionsForRow(CQL3CasRequest.java:138)
> ~[main/:na]
> at
> org.apache.cassandra.cql3.statements.CQL3CasRequest.addExistsCondition(CQL3CasRequest.java:104)
> ~[main/:na]
> at
> org.apache.cassandra.cql3.statements.CQL3CasRequest.addNotExist(CQL3CasRequest.java:84)
> ~[main/:na]
> at
> org.apache.cassandra.cql3.IfNotExistsCondition.addConditionsTo(IfNotExistsCondition.java:28)
> ~[main/:na]
> at
> org.apache.cassandra.cql3.statements.ModificationStatement.addConditions(ModificationStatement.java:482)
> ~[main/:na]
> at
> org.apache.cassandra.cql3.statements.BatchStatement.makeCasRequest(BatchStatement.java:434)
> ~[main/:na]
> at
> org.apache.cassandra.cql3.statements.BatchStatement.executeWithConditions(BatchStatement.java:379)
> ~[main/:na]
> at
> org.apache.cassandra.cql3.statements.BatchStatement.execute(BatchStatement.java:358)
> ~[main/:na]
> at
> org.apache.cassandra.cql3.statements.BatchStatement.execute(BatchStatement.java:346)
> ~[main/:na]
> at
> org.apache.cassandra.cql3.statements.BatchStatement.execute(BatchStatement.java:341)
> ~[main/:na]
> at
> org.apache.cassandra.cql3.QueryProcessor.processStatement(QueryProcessor.java:218)
> ~[main/:na]
> at
> org.apache.cassandra.cql3.QueryProcessor.process(QueryProcessor.java:249)
> ~[main/:na]
> at
> org.apache.cassandra.cql3.QueryProcessor.process(QueryProcessor.java:234)
> ~[main/:na]
> at
> org.apache.cassandra.transport.messages.QueryMessage.execute(QueryMessage.java:115)
> ~[main/:na]
> at
> org.apache.cassandra.transport.Message$Dispatcher.channelRead0(Message.java:516)
> [main/:na]
> at
> org.apache.cassandra.transport.Message$Dispatcher.channelRead0(Message.java:409)
> [main/:na]
> at
> io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105)
> [netty-all-4.0.39.Final.jar:4.0.39.Final]
> at
> io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:366)
> [netty-all-4.0.39.Final.jar:4.0.39.Final]
> at
> io.netty.channel.AbstractChannelHandlerContext.access$600(AbstractChannelHandlerContext.java:35)
> [netty-all-4.0.39.Final.jar:4.0.39.Final]
> at
> io.netty.channel.AbstractChannelHandlerContext$7.run(AbstractChannelHandlerContext.java:357)
> [netty-all-4.0.39.Final.jar:4.0.39.Final]
> at
> java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
> [na:1.8.0_102]
> at
> org.apache.cassandra.concurrent.AbstractLocalAwareExecutorService$FutureTask.run(AbstractLocalAwareExecutorService.java:162)
> [main/:na]
> at org.apache.cassandra.concurrent.SEPWorker.run(SEPWorker.java:109)
> [main/:na]
> at java.lang.Thread.run(Thread.java:745) [na:1.8.0_102]
> {code}
> The problem is that previous will receive a value after the first statement
> in the batch is evaluated in BatchStatement.makeCasRequest. I can't see any
> reason why we have this assertion, it seems to me that it's unnecessary.
> Removing it fixes the problem (obviously) but I'm not sure if it breaks
> something else, or if this is an intended failure case (in which case it
> should be caught earlier on).
> Relevant code is as follows:
> {code:title=CQL3CasRequest.java}
> private void setConditionsForRow(Clustering clustering, RowCondition
> condition)
> {
> if (clustering == Clustering.STATIC_CLUSTERING)
> {
> assert staticConditions == null;
> staticConditions = condition;
> }
> else
> {
> RowCondition previous = conditions.put(clustering, condition);
> assert previous == null;
> }
> }
> {code}
> I've attached a patch that fixes the issue by removing the assert
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