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From "Tijmen R (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (SQOOP-3320) Commit behaviour leads to exceptions on read-only database
Date Thu, 26 Apr 2018 21:34:00 GMT

     [ https://issues.apache.org/jira/browse/SQOOP-3320?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Tijmen R updated SQOOP-3320:
----------------------------
    Attachment: SQOOP-3320.patch

> Commit behaviour leads to exceptions on read-only database
> ----------------------------------------------------------
>
>                 Key: SQOOP-3320
>                 URL: https://issues.apache.org/jira/browse/SQOOP-3320
>             Project: Sqoop
>          Issue Type: Bug
>          Components: connectors/generic
>    Affects Versions: 1.4.7
>            Reporter: Tijmen R
>            Priority: Major
>              Labels: newbie
>         Attachments: SQOOP-3320.patch
>
>
> The current Sqoop behaviour is to do a commit after having retrieved the results of a
query. This leads to errors when the database (or the connection) is in read-only mode.
> Example stack traces:
> {code:java}
> ERROR manager.SqlManager: SQLException closing ResultSet: org.netezza.error.NzSQLException:
ERROR:  Database 'XXXPRD' is available for read-only
>         at org.netezza.internal.QueryExecutor.getNextResult(QueryExecutor.java:280)
>         at org.netezza.internal.QueryExecutor.execute(QueryExecutor.java:76)
>         at org.netezza.sql.NzConnection.execute(NzConnection.java:2819)
>         at org.netezza.sql.NzConnection.execute(NzConnection.java:2791)
>         at org.netezza.sql.NzConnection.commit(NzConnection.java:1161)
>         at org.apache.sqoop.manager.SqlManager.getColumnNamesForRawQuery(SqlManager.java:182)
>         at org.apache.sqoop.manager.SqlManager.getColumnNamesForQuery(SqlManager.java:142)
> {code}
> {code:java}
> tool.EvalSqlTool: SQL exception executing statement: org.netezza.error.NzSQLException:
ERROR:  Database 'XXXPRD' is available for read-only         at org.netezza.internal.QueryExecutor.getNextResult(QueryExecutor.java:280)
        at org.netezza.internal.QueryExecutor.execute(QueryExecutor.java:76)        
at org.netezza.sql.NzConnection.execute(NzConnection.java:2819)         at org.netezza.sql.NzConnection.execute(NzConnection.java:2791)
        at org.netezza.sql.NzConnection.commit(NzConnection.java:1161)        
at org.apache.sqoop.tool.EvalSqlTool.run(EvalSqlTool.java:78)         at org.apache.sqoop.Sqoop.run(Sqoop.java:147)
>  
> {code}
>  
> When using _sqoop eval_, it is not a major issue since it happens after the data is already
fetched and displayed. When using _sqoop import_ however, the spawned mapreduce jobs all fail,
so this is blocking the whole import.
> This commit behaviour exists in several methods, at least the following:
> org.apache.sqoop.tool.EvalSqlTool::run (line 78)
> org.apache.sqoop.mapreduce.db.DBRecordReader::close (line 169)
> org.apache.sqoop.manager.SqlManager::getColumnNamesForRawQuery (line 182)
> org.apache.sqoop.manager.SqlManager::getColumnInfoForRawQuery
> org.apache.sqoop.manager.SqlManager::getColumnNamesForProcedure (line 226)
>  
> When a connection is in autocommit mode, then a manual commit is not needed anyway. When
a connection is in read-only mode, then it should still be possible to do a rollback in order
to close an outstanding transaction.
> I propose to change the mentioned method lines ("connection.commit();" or equivalent),
to:
> {code:java}
> if (!connection.getAutoCommit()) {
>   if (connection.isReadOnly())
>     connection.rollback();
>   else
>     connection.commit();
> }
> {code}
> (or equivalent)
>  
> (Overall, I don't know why a commit is done in the above mentioned methods, as data should
have only been read, if the idea is to just close the transaction, why not do a rollback instead
just as a safety measure?)



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