[ 
https://issues.apache.org/jira/browse/HIVE-23873?focusedWorklogId=465559&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-465559
 ]

ASF GitHub Bot logged work on HIVE-23873:
-----------------------------------------

                Author: ASF GitHub Bot
            Created on: 03/Aug/20 06:24
            Start Date: 03/Aug/20 06:24
    Worklog Time Spent: 10m 
      Work Description: shameersss1 commented on a change in pull request #1328:
URL: https://github.com/apache/hive/pull/1328#discussion_r464215422



##########
File path: 
jdbc-handler/src/main/java/org/apache/hive/storage/jdbc/dao/JdbcRecordIterator.java
##########
@@ -59,9 +62,26 @@ public JdbcRecordIterator(Connection conn, PreparedStatement 
ps, ResultSet rs, C
       fieldNamesProperty = 
Preconditions.checkNotNull(conf.get(Constants.JDBC_QUERY_FIELD_NAMES));
       fieldTypesProperty = 
Preconditions.checkNotNull(conf.get(Constants.JDBC_QUERY_FIELD_TYPES));
     } else {
-      fieldNamesProperty = 
Preconditions.checkNotNull(conf.get(serdeConstants.LIST_COLUMNS));
+      try {
+        if (conf.get(Constants.JDBC_QUERY) == null) {
+          ResultSetMetaData metadata = rs.getMetaData();
+          int numColumns = metadata.getColumnCount();
+          List<String> columnNames = new ArrayList<String>(numColumns);
+          for (int i = 0; i < numColumns; i++) {
+            columnNames.add(metadata.getColumnName(i + 1));
+          }
+          fieldNamesProperty = String.join(",",columnNames);

Review comment:
       nit: space missing:  **String.join(",", columnNames);**




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Issue Time Tracking
-------------------

    Worklog Id:     (was: 465559)
    Time Spent: 1h 10m  (was: 1h)

> Querying Hive JDBCStorageHandler table fails with NPE when CBO is off
> ---------------------------------------------------------------------
>
>                 Key: HIVE-23873
>                 URL: https://issues.apache.org/jira/browse/HIVE-23873
>             Project: Hive
>          Issue Type: Bug
>          Components: HiveServer2, JDBC
>    Affects Versions: 3.1.0, 3.1.1, 3.1.2
>            Reporter: Chiran Ravani
>            Assignee: Chiran Ravani
>            Priority: Critical
>              Labels: pull-request-available
>         Attachments: HIVE-23873.01.patch, HIVE-23873.02.patch, 
> HIVE-23873.3.patch, HIVE-23873.4.patch
>
>          Time Spent: 1h 10m
>  Remaining Estimate: 0h
>
> Scenario is Hive table having same schema as table in Oracle, however when we 
> query the table with data it fails with NPE, below is the trace.
> {code}
> Caused by: java.io.IOException: java.lang.NullPointerException
>         at 
> org.apache.hadoop.hive.ql.exec.FetchOperator.getNextRow(FetchOperator.java:617)
>  ~[hive-exec-3.1.0.3.1.5.0-152.jar:3.1.0.3.1.5.0-152]
>         at 
> org.apache.hadoop.hive.ql.exec.FetchOperator.pushRow(FetchOperator.java:524) 
> ~[hive-exec-3.1.0.3.1.5.0-152.jar:3.1.0.3.1.5.0-152]
>         at org.apache.hadoop.hive.ql.exec.FetchTask.fetch(FetchTask.java:146) 
> ~[hive-exec-3.1.0.3.1.5.0-152.jar:3.1.0.3.1.5.0-152]
>         at org.apache.hadoop.hive.ql.Driver.getResults(Driver.java:2739) 
> ~[hive-exec-3.1.0.3.1.5.0-152.jar:3.1.0.3.1.5.0-152]
>         at 
> org.apache.hadoop.hive.ql.reexec.ReExecDriver.getResults(ReExecDriver.java:229)
>  ~[hive-exec-3.1.0.3.1.5.0-152.jar:3.1.0.3.1.5.0-152]
>         at 
> org.apache.hive.service.cli.operation.SQLOperation.getNextRowSet(SQLOperation.java:473)
>  ~[hive-service-3.1.0.3.1.5.0-152.jar:3.1.0.3.1.5.0-152]
>         ... 34 more
> Caused by: java.lang.NullPointerException
>         at 
> org.apache.hive.storage.jdbc.JdbcSerDe.deserialize(JdbcSerDe.java:164) 
> ~[hive-jdbc-handler-3.1.0.3.1.5.0-152.jar:3.1.0.3.1.5.0-152]
>         at 
> org.apache.hadoop.hive.ql.exec.FetchOperator.getNextRow(FetchOperator.java:598)
>  ~[hive-exec-3.1.0.3.1.5.0-152.jar:3.1.0.3.1.5.0-152]
>         at 
> org.apache.hadoop.hive.ql.exec.FetchOperator.pushRow(FetchOperator.java:524) 
> ~[hive-exec-3.1.0.3.1.5.0-152.jar:3.1.0.3.1.5.0-152]
>         at org.apache.hadoop.hive.ql.exec.FetchTask.fetch(FetchTask.java:146) 
> ~[hive-exec-3.1.0.3.1.5.0-152.jar:3.1.0.3.1.5.0-152]
>         at org.apache.hadoop.hive.ql.Driver.getResults(Driver.java:2739) 
> ~[hive-exec-3.1.0.3.1.5.0-152.jar:3.1.0.3.1.5.0-152]
>         at 
> org.apache.hadoop.hive.ql.reexec.ReExecDriver.getResults(ReExecDriver.java:229)
>  ~[hive-exec-3.1.0.3.1.5.0-152.jar:3.1.0.3.1.5.0-152]
>         at 
> org.apache.hive.service.cli.operation.SQLOperation.getNextRowSet(SQLOperation.java:473)
>  ~[hive-service-3.1.0.3.1.5.0-152.jar:3.1.0.3.1.5.0-152]
>         ... 34 more
> {code}
> Problem appears when column names in Oracle are in Upper case and since in 
> Hive, table and column names are forced to store in lowercase during 
> creation. User runs into NPE error while fetching data.
> While deserializing data, input consists of column names in lower case which 
> fails to get the value
> https://github.com/apache/hive/blob/rel/release-3.1.2/jdbc-handler/src/main/java/org/apache/hive/storage/jdbc/JdbcSerDe.java#L136
> {code}
> rowVal = ((ObjectWritable)value).get();
> {code}
> Log Snio:
> =============
> {code}
> 2020-07-17T16:49:09,598 INFO  [04ed42ec-91d2-4662-aee7-37e840a06036 
> HiveServer2-Handler-Pool: Thread-104]: dao.GenericJdbcDatabaseAccessor (:()) 
> - Query to execute is [select * from TESTHIVEJDBCSTORAGE]
> 2020-07-17T16:49:10,642 INFO  [04ed42ec-91d2-4662-aee7-37e840a06036 
> HiveServer2-Handler-Pool: Thread-104]: jdbc.JdbcSerDe (:()) - *** ColumnKey = 
> ID
> 2020-07-17T16:49:10,642 INFO  [04ed42ec-91d2-4662-aee7-37e840a06036 
> HiveServer2-Handler-Pool: Thread-104]: jdbc.JdbcSerDe (:()) - *** Blob value 
> = {fname=OW[class=class java.lang.String,value=Name1], id=OW[class=class 
> java.lang.Integer,value=1]}
> {code}
> Simple Reproducer for this case.
> =============
> 1. Create table in Oracle
> {code}
> create table TESTHIVEJDBCSTORAGE(ID INT, FNAME VARCHAR(20));
> {code}
> 2. Insert dummy data.
> {code}
> Insert into TESTHIVEJDBCSTORAGE values (1, 'Name1');
> {code}
> 3. Create JDBCStorageHandler table in Hive.
> {code}
> CREATE EXTERNAL TABLE default.TESTHIVEJDBCSTORAGE_HIVE_TBL (ID INT, FNAME 
> VARCHAR(20)) 
> STORED BY 'org.apache.hive.storage.jdbc.JdbcStorageHandler' 
> TBLPROPERTIES ( 
> "hive.sql.database.type" = "ORACLE", 
> "hive.sql.jdbc.driver" = "oracle.jdbc.OracleDriver", 
> "hive.sql.jdbc.url" = "jdbc:oracle:thin:@orachehostname/XE", 
> "hive.sql.dbcp.username" = "chiran", 
> "hive.sql.dbcp.password" = "supersecurepassword", 
> "hive.sql.table" = "TESTHIVEJDBCSTORAGE", 
> "hive.sql.dbcp.maxActive" = "1" 
> );
> {code}
> 4. Query Hive table, fails with NPE.
> {code}
> > select * from default.TESTHIVEJDBCSTORAGE_HIVE_TBL;
> INFO  : Compiling 
> command(queryId=hive_20200717164857_cd6f5020-4a69-4a2d-9e63-9db99d0121bc): 
> select * from default.TESTHIVEJDBCSTORAGE_HIVE_TBL
> INFO  : Semantic Analysis Completed (retrial = false)
> INFO  : Returning Hive schema: 
> Schema(fieldSchemas:[FieldSchema(name:testhivejdbcstorage_hive_tbl.id, 
> type:int, comment:null), FieldSchema(name:testhivejdbcstorage_hive_tbl.fname, 
> type:varchar(20), comment:null)], properties:null)
> INFO  : Completed compiling 
> command(queryId=hive_20200717164857_cd6f5020-4a69-4a2d-9e63-9db99d0121bc); 
> Time taken: 9.914 seconds
> INFO  : Executing 
> command(queryId=hive_20200717164857_cd6f5020-4a69-4a2d-9e63-9db99d0121bc): 
> select * from default.TESTHIVEJDBCSTORAGE_HIVE_TBL
> INFO  : Completed executing 
> command(queryId=hive_20200717164857_cd6f5020-4a69-4a2d-9e63-9db99d0121bc); 
> Time taken: 0.019 seconds
> INFO  : OK
> Error: java.io.IOException: java.lang.NullPointerException (state=,code=0)
> {code}
> Assuming that there are no repercussions, can we convert the column names to 
> lowercase fetched from Database/Query pointing to table in JDBCStorageHandler?
> Attaching the patch for the case.



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