1. 在使用INSERT OVERWRITE DIRECTORY语句的时候报出如下异常
Caused by: java.io.IOException: Cannot get DistCp constructor: org.apache.hadoop.tools.DistCp.<init>()
at org.apache.hadoop.hive.shims.Hadoop23Shims.runDistCp(Hadoop23Shims.java:1160)
at org.apache.hadoop.hive.common.FileUtils.copy(FileUtils.java:553)
at org.apache.hadoop.hive.ql.metadata.Hive.moveFile(Hive.java:2622)
... 21 more环境：hive-1.2.1 hadoop-2.7.2
错误原因：
hadoop-2.7.2源代码中org.apache.hadoop.tools.DistCp的无参构造方法已经取消public。
/**
* To be used with the ToolRunner. Not for public consumption.
*/
@VisibleForTesting
DistCp() {}而hive-1.2.1中使用反射机制初始化org.apache.hadoop.tools.DistCp时，调用的正是无参构造方法。
@Override
public boolean runDistCp(Path src, Path dst, Configuration conf) throws IOException {
int rc;
// Creates the command-line parameters for distcp
String[] params = {"-update", "-skipcrccheck", src.toString(), dst.toString()};
try {
Class clazzDistCp = Class.forName("org.apache.hadoop.tools.DistCp");
Constructor c = clazzDistCp.getConstructor();
c.setAccessible(true);
Tool distcp = (Tool)c.newInstance();
distcp.setConf(conf);
rc = distcp.run(params);
} catch (ClassNotFoundException e) {
throw new IOException("Cannot find DistCp class package: " + e.getMessage());
} catch (NoSuchMethodException e) {
throw new IOException("Cannot get DistCp constructor: " + e.getMessage());
} catch (Exception e) {
throw new IOException("Cannot execute DistCp process: " + e, e);
}
return (0 == rc);
}解决方案：使用老版本的hadoop-distcp-x.x.x.jar，我这里使用的是hadoop-distcp-2.6.2.jar。
@VisibleForTesting
public DistCp() {}
