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https://issues.apache.org/jira/browse/PIG-72?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12570869#action_12570869
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Xu Zhang commented on PIG-72:
-----------------------------
Exceptions like the following happen with the recent Pig revisions.
{code}
Caused an ERROR
java.io.IOException cannot be cast to java.lang.Error
java.lang.ClassCastException: java.io.IOException cannot be cast to
java.lang.Error
at
org.apache.pig.impl.logicalLayer.parser.QueryParser.LoadClause(QueryParser.java:646)
at
org.apache.pig.impl.logicalLayer.parser.QueryParser.BaseExpr(QueryParser.java:495)
at
org.apache.pig.impl.logicalLayer.parser.QueryParser.NestedExpr(QueryParser.java:423)
at
org.apache.pig.impl.logicalLayer.parser.QueryParser.ForEachClause(QueryParser.java:1348)
at
org.apache.pig.impl.logicalLayer.parser.QueryParser.BaseExpr(QueryParser.java:550)
at
org.apache.pig.impl.logicalLayer.parser.QueryParser.Expr(QueryParser.java:371)
at
org.apache.pig.impl.logicalLayer.parser.QueryParser.Parse(QueryParser.java:227)
at
org.apache.pig.impl.logicalLayer.LogicalPlanBuilder.parse(LogicalPlanBuilder.java:47)
at org.apache.pig.PigServer.registerQuery(PigServer.java:228)
at
org.apache.pig.test.TestInfixArithmetic.testSubtract(TestInfixArithmetic.java:71)
{code}
The exceptions occur in this scenario: The 1st test method that calls
registerQuery() will pass, but the subsequent test method(s) that call
registerQuery() will get this kind of exception. For example,
{code}
// The 1st test method that calls registerQuery() will pass with no
exception
public void testSimpleCount() throws Throwable {
PigServer pig = new PigServer("mapreduce");
...
pig.registerQuery(query);
....
}
// The 2nd and following test methods that call registerQuery() will get
the exception
public void testGroupCount() throws Throwable {
PigServer pig = new PigServer("mapreduce");
...
pig.registerQuery(query);
....
}
...
{code}
On line 646 of QueryParser.java, the program tries to cast an IOException into
an Error which generates this exception. This exception did not occur with the
earlier revisions of Pig. Does anyone have any idea what the root cause is for
this kind of exceptions and how to avoid it?
> Porting Pig unit tests to use MiniDFSCluster and MiniMRCluster on the local
> machine
> -----------------------------------------------------------------------------------
>
> Key: PIG-72
> URL: https://issues.apache.org/jira/browse/PIG-72
> Project: Pig
> Issue Type: Test
> Components: tools
> Reporter: Xu Zhang
> Attachments: hadoop-0.15.3-dev-test-utils.jar,
> PortPigUnitTestToMiniClusters.patch,
> TEST-org.apache.pig.test.TestAlgebraicEval.txt
>
>
> We have the need to port the Pig unit tests to use MiniDFSCluster and
> MiniMRCluster, so that tests can be executed with the DFS and MR threads on
> the local machine. This feature will eliminate the need to set up a real
> distributed hadoop cluster before running the unit tests, as everything will
> now be carried out with the (mini) cluster on the user's local machine.
> One prerequisite for using this feature is a hadoop jar that has the class
> files for MiniDFSCluster, MiniMRCluster and other supporting components. I
> have been able to generate such a jar file with a special target added by
> myself to hadoop's build.xml and have also logged a hadoop jira to request
> this target be a permanent part of that build file. If possible, we can just
> replace hadoop15.jar with this jar file on the SVN source tree and then the
> users will never need to worry about the availability of this jar file.
> Please find such a hadoop jar file in the attachment.
> To use the feature in unit tests, the user just need to call
> MiniClusterBuilder.buildCluster() before a PigServer instance is created with
> the string "mapreduce" as the parameter to its constructor. Here is an
> example of how the MiniClusterBuilder is used in a test case class:
> public class TestWhatEver extends TestCase {
> private String initString = "mapreduce";
> private MiniClusterBuilder cluster =
> MiniClusterBuilder.buildCluster();
>
> @Test
> public void testGroupCountWithMultipleFields() throws
> Exception {
> PigServer pig = new PigServer(initString);
> // Do something with the pig server, such as
> registering and executing Pig
> // queries. The queries will executed with the local
> cluster.
> }
>
> // More test cases if needed
> }
> To run the unit tests with the local cluster, under the top directory of the
> source tree, issue the command "ant test". Notice that you do not need to
> specify the location of the hadoop-site.xml file with the command line option
> "-Djunit.hadoop.conf=<dir>" anymore.
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