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From "Benjamin Lerer (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8090) NullPointerException when using prepared statements
Date Fri, 17 Oct 2014 15:46:35 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8090?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14175172#comment-14175172
] 

Benjamin Lerer commented on CASSANDRA-8090:
-------------------------------------------

With the fact that functions can be nested within functions you end up with a tree structure
of Selectors were each one of them might or might not need to store some state.
The first approach to solve that problem is to use a Map to store the state and to pass that
map to each selector.
The problems that I see with that approach is that we will end up doing a lot of map lookups
(e.g. if we have 5 columns and 10 000 rows we will end up doing 50 000 map lookups). To avoid
that performance cost I tried to have a state container which is somehow iterable in the selector
order but as the selectors have a tree structure the result that I got was looking a bit hacky
and it was alway involving casting each time we were retrieving the state (which I found quite
ugly)
As we were any way forced to create the same (or a bit less) number of state objects than
selectors I choosed to keep the state and the method together and to create a new set of selectors
each time but for that I needed a factory.    

> NullPointerException when using prepared statements
> ---------------------------------------------------
>
>                 Key: CASSANDRA-8090
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8090
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Carl Yeksigian
>            Assignee: Benjamin Lerer
>             Fix For: 3.0
>
>
> Due to the changes in CASSANDRA-4914, using a prepared statement from multiple threads
leads to a race condition where the simple selection may be reset from a different thread,
causing the following NPE:
> {noformat}
> java.lang.NullPointerException: null
> 	at org.apache.cassandra.cql3.ResultSet.addRow(ResultSet.java:63) ~[main/:na]
> 	at org.apache.cassandra.cql3.statements.Selection$ResultSetBuilder.build(Selection.java:372)
~[main/:na]
> 	at org.apache.cassandra.cql3.statements.SelectStatement.process(SelectStatement.java:1120)
~[main/:na]
> 	at org.apache.cassandra.cql3.statements.SelectStatement.processResults(SelectStatement.java:283)
~[main/:na]
> 	at org.apache.cassandra.cql3.statements.SelectStatement.execute(SelectStatement.java:260)
~[main/:na]
> 	at org.apache.cassandra.cql3.statements.SelectStatement.execute(SelectStatement.java:213)
~[main/:na]
> 	at org.apache.cassandra.cql3.statements.SelectStatement.execute(SelectStatement.java:63)
~[main/:na]
> 	at org.apache.cassandra.cql3.QueryProcessor.processStatement(QueryProcessor.java:226)
~[main/:na]
> 	at org.apache.cassandra.cql3.QueryProcessor.processPrepared(QueryProcessor.java:481)
~[main/:na]
> 	at org.apache.cassandra.transport.messages.ExecuteMessage.execute(ExecuteMessage.java:133)
~[main/:na]
> 	at org.apache.cassandra.transport.Message$Dispatcher.channelRead0(Message.java:438)
[main/:na]
> 	at org.apache.cassandra.transport.Message$Dispatcher.channelRead0(Message.java:334)
[main/:na]
> 	at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105)
[netty-all-4.0.23.Final.jar:4.0.23.Final]
> 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333)
[netty-all-4.0.23.Final.jar:4.0.23.Final]
> 	at io.netty.channel.AbstractChannelHandlerContext.access$700(AbstractChannelHandlerContext.java:32)
[netty-all-4.0.23.Final.jar:4.0.23.Final]
> 	at io.netty.channel.AbstractChannelHandlerContext$8.run(AbstractChannelHandlerContext.java:324)
[netty-all-4.0.23.Final.jar:4.0.23.Final]
> 	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) [na:1.7.0_67]
> 	at org.apache.cassandra.concurrent.AbstractTracingAwareExecutorService$FutureTask.run(AbstractTracingAwareExecutorService.java:163)
[main/:na]
> 	at org.apache.cassandra.concurrent.SEPWorker.run(SEPWorker.java:103) [main/:na]
> 	at java.lang.Thread.run(Thread.java:745) [na:1.7.0_67]
> {noformat}
> Reproduced this using the stress tool:
> {noformat}
>  ./tools/bin/cassandra-stress user profile=tools/cqlstress-example.yaml ops\(insert=1,simple1=1\)
> {noformat}
> You'll need to change the {noformat}select:{noformat} line to be /1000 to prevent the
illegal query exceptions.



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