hadoop - HIVE中的MAP SIDE JOIN中的错误

Question

我发现如果要仅在join中运行 map 阶段，则必须设置以下属性.reduce = 0。然后我收到如下错误。如果我将该属性设置为false map-reduce run并且连接成功发生。

hive> set hive.auto.convert.join=true; 

hive> set hive.mapjoin.smalltable.filesize=(default it will be 25MB);
Query returned non-zero code: 1, cause: 'SET hive.mapjoin.smalltable.filesize=(default it will be 25MB)' FAILED because hive.mapjoin.smalltable.filesize expects LONG type value.
hive> SELECT /*+ MAPJOIN(expense) */ c.ID, c.NAME, o.AMOUNT, o.DATE FROM emp c CROSS JOIN expense o ON (c.ID = o.emp_ID);
Query ID = acadgild_20161226234949_6ede202c-7f91-42ac-a0c9-3b2617fad0ae
Total jobs = 1
java.io.IOException: Cannot run program "/home/acadgild/hadoop-2.6.0/bin/hadoop" (in directory "/home/acadgild"): error=2, No such file or directory
    at java.lang.ProcessBuilder.start(ProcessBuilder.java:1048)
    at java.lang.Runtime.exec(Runtime.java:620)
    at java.lang.Runtime.exec(Runtime.java:450)
    at org.apache.hadoop.hive.ql.exec.mr.MapredLocalTask.executeInChildVM(MapredLocalTask.java:289)
    at org.apache.hadoop.hive.ql.exec.mr.MapredLocalTask.execute(MapredLocalTask.java:137)
    at org.apache.hadoop.hive.ql.exec.Task.executeTask(Task.java:160)
    at org.apache.hadoop.hive.ql.exec.TaskRunner.runSequential(TaskRunner.java:85)
    at org.apache.hadoop.hive.ql.Driver.launchTask(Driver.java:1604)
    at org.apache.hadoop.hive.ql.Driver.execute(Driver.java:1364)
    at org.apache.hadoop.hive.ql.Driver.runInternal(Driver.java:1177)
    at org.apache.hadoop.hive.ql.Driver.run(Driver.java:1004)
    at org.apache.hadoop.hive.ql.Driver.run(Driver.java:994)
    at org.apache.hadoop.hive.cli.CliDriver.processLocalCmd(CliDriver.java:247)
    at org.apache.hadoop.hive.cli.CliDriver.processCmd(CliDriver.java:199)
    at org.apache.hadoop.hive.cli.CliDriver.processLine(CliDriver.java:410)
    at org.apache.hadoop.hive.cli.CliDriver.executeDriver(CliDriver.java:783)
    at org.apache.hadoop.hive.cli.CliDriver.run(CliDriver.java:677)
    at org.apache.hadoop.hive.cli.CliDriver.main(CliDriver.java:616)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.apache.hadoop.util.RunJar.run(RunJar.java:221)
    at org.apache.hadoop.util.RunJar.main(RunJar.java:136)
Caused by: java.io.IOException: error=2, No such file or directory
    at java.lang.UNIXProcess.forkAndExec(Native Method)
    at java.lang.UNIXProcess.<init>(UNIXProcess.java:248)
    at java.lang.ProcessImpl.start(ProcessImpl.java:134)
    at java.lang.ProcessBuilder.start(ProcessBuilder.java:1029)
    ... 23 more
FAILED: Execution Error, return code 1 from org.apache.hadoop.hive.ql.exec.mr.MapredLocalTask
hive> set hive.auto.convert.join=false;                                                                                  
hive>

Answer 1

Hive中的Map Side Join可以通过两种方式执行。

通过在join语句中指定关键字/*+ MAPJOIN(b) */。

通过将以下属性设置为true。

hive.auto.convert.join = true

我认为您正在尝试将这两种方式结合起来。请检查此博客以获取更多信息 link

希望这可以帮助。