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https://issues.apache.org/jira/browse/HIVE-6050?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13863426#comment-13863426
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Carl Steinbach commented on HIVE-6050:
--------------------------------------

It looks like Thrift IDL is not backward compatible wrt to Enums. We use Enums 
in other places in the IDL (e.g. TTypeId, TStatusCode, TOperationState, 
TOperationType, TGetTypeInfo, TFetchOrientation), and should probably 
investigate whether these references need to updated as well. I'm convinced 
that using an Enum for TGetTypeInfo was a bad idea, and suspect that the same 
may also be true for TTypeId.

> JDBC backward compatibility is broken
> -------------------------------------
>
>                 Key: HIVE-6050
>                 URL: https://issues.apache.org/jira/browse/HIVE-6050
>             Project: Hive
>          Issue Type: Bug
>          Components: HiveServer2, JDBC
>            Reporter: Szehon Ho
>            Priority: Blocker
>
> Connect from JDBC driver of Hive 0.13 (TProtocolVersion=v4) to HiveServer2 of 
> Hive 0.10 (TProtocolVersion=v1), will return the following exception:
> {noformat}
> java.sql.SQLException: Could not establish connection to 
> jdbc:hive2://localhost:10000/default: Required field 'client_protocol' is 
> unset! Struct:TOpenSessionReq(client_protocol:null)
>       at 
> org.apache.hive.jdbc.HiveConnection.openSession(HiveConnection.java:336)
>       at org.apache.hive.jdbc.HiveConnection.<init>(HiveConnection.java:158)
>       at org.apache.hive.jdbc.HiveDriver.connect(HiveDriver.java:105)
>       at java.sql.DriverManager.getConnection(DriverManager.java:571)
>       at java.sql.DriverManager.getConnection(DriverManager.java:187)
>       at 
> org.apache.hive.jdbc.MyTestJdbcDriver2.getConnection(MyTestJdbcDriver2.java:73)
>       at 
> org.apache.hive.jdbc.MyTestJdbcDriver2.&lt;init&gt;(MyTestJdbcDriver2.java:49)
>       at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
>       at 
> sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
>       at 
> sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
>       at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
>       at 
> org.junit.runners.BlockJUnit4ClassRunner.createTest(BlockJUnit4ClassRunner.java:187)
>       at 
> org.junit.runners.BlockJUnit4ClassRunner$1.runReflectiveCall(BlockJUnit4ClassRunner.java:236)
>       at 
> org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
>       at 
> org.junit.runners.BlockJUnit4ClassRunner.methodBlock(BlockJUnit4ClassRunner.java:233)
>       at 
> org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
>       at 
> org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
>       at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
>       at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
>       at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
>       at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
>       at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
>       at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
>       at junit.framework.JUnit4TestAdapter.run(JUnit4TestAdapter.java:39)
>       at 
> org.apache.tools.ant.taskdefs.optional.junit.JUnitTestRunner.run(JUnitTestRunner.java:523)
>       at 
> org.apache.tools.ant.taskdefs.optional.junit.JUnitTestRunner.launch(JUnitTestRunner.java:1063)
>       at 
> org.apache.tools.ant.taskdefs.optional.junit.JUnitTestRunner.main(JUnitTestRunner.java:914)
> Caused by: org.apache.thrift.TApplicationException: Required field 
> 'client_protocol' is unset! Struct:TOpenSessionReq(client_protocol:null)
>       at 
> org.apache.thrift.TApplicationException.read(TApplicationException.java:108)
>       at org.apache.thrift.TServiceClient.receiveBase(TServiceClient.java:71)
>       at 
> org.apache.hive.service.cli.thrift.TCLIService$Client.recv_OpenSession(TCLIService.java:160)
>       at 
> org.apache.hive.service.cli.thrift.TCLIService$Client.OpenSession(TCLIService.java:147)
>       at 
> org.apache.hive.jdbc.HiveConnection.openSession(HiveConnection.java:327)
>       ... 37 more
> {noformat}
> On code analysis, it looks like the 'client_protocol' scheme is a ThriftEnum, 
> which doesn't seem to be backward-compatible.  Look at the code path in the 
> generated file 'TOpenSessionReq.java', method 
> TOpenSessionReqStandardScheme.read():
> 1. The method will call 'TProtocolVersion.findValue()' on the thrift 
> protocol's byte stream, which returns null if the client is sending an enum 
> value unknown to the server.  (v4 is unknown to server)
> 2. The method will then call struct.validate(), which will throw the above 
> exception because of null version.  
> So doesn't look like the current backward-compatibility scheme will work.



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