https://community.cloudera.com/t5/Support-Questions/What-is-col0-in-hive-explain-plan/m-p/191218#M153307 <P><A rel="user" href="https://community.cloudera.com/users/294/ghagleitner.html" nodeid="294">@Gunther Hagleitner</A></P><P>See error below:</P><PRE>0: jdbc:hive2://localhost:10000&gt; select count(*) from db1.table1; Waiting to acquire compile lock. Acquired the compile lock. ---------------------------------------------------------------------------------------------- VERTICES MODE STATUS TOTAL COMPLETED RUNNING PENDING FAILED KILLED ---------------------------------------------------------------------------------------------- Map 1 ......... container RUNNING 1034 1010 0 24 39 0 Reducer 2 container INITED 1 0 0 1 0 0 ---------------------------------------------------------------------------------------------- VERTICES: 00/02 [=========================&gt;&gt;-] 97% ELAPSED TIME: 53.36 s ---------------------------------------------------------------------------------------------- Error: org.apache.hive.service.cli.HiveSQLException: Error while processing statement: FAILED: Execution Error, return code 2 from org.apache.hadoop.hive.ql.exec.tez.TezTask. Vertex failed, vertexName=Map 1, vertexId=vertex_1525980884509_57715_1_00, diagnostics=[Task failed, taskId=task_1525980884509_57715_1_00_000565, diagnostics=[TaskAttempt 0 failed, info=[Container container_1525980884509_57715_01_000003 finished with diagnostics set to [Container failed, exitCode=-104. Container [pid=14308,containerID=container_1525980884509_57715_01_000003] is running beyond physical memory limits. Current usage: 1.6 GB of 1.5 GB physical memory used; 3.5 GB of 7.5 GB virtual memory used. Killing container. Dump of the process-tree for container_1525980884509_57715_01_000003 : </PRE><P>I too agree that its weird a simple count(*) is getting OOM. Interestingly, if i do something like the below, it counts fine:</P><PRE>0: jdbc:hive2://localhost:10000&gt; select sum(cnt) from (select count(*) cnt, run_detail_id from db1.table1 group by run_detail_id) a; Waiting to acquire compile lock. Acquired the compile lock. ---------------------------------------------------------------------------------------------- VERTICES MODE STATUS TOTAL COMPLETED RUNNING PENDING FAILED KILLED ---------------------------------------------------------------------------------------------- Map 1 .......... container SUCCEEDED 1034 1034 0 0 0 0 Reducer 2 ...... container SUCCEEDED 211 211 0 0 0 0 Reducer 3 ...... container SUCCEEDED 1 1 0 0 0 0 ---------------------------------------------------------------------------------------------- VERTICES: 03/03 [==========================&gt;&gt;] 100% ELAPSED TIME: 47.64 s ---------------------------------------------------------------------------------------------- +------------+ | _c0 | +------------+ | 227394274 | +------------+ </PRE> Wed, 16 May 2018 04:02:44 GMT crayonml 2018-05-16T04:02:44Z