[NIFI-1412] JdbcCommon.createSchema() throws exception when no columns are present

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.5.0
• Assignee: Unassigned
• Reporter: Matt Burgess
• Created: 19/Jan/16 16:49
• Updated: 26/Jan/16 17:30
• Resolved: 26/Jan/16 17:30

Description

The discovery of the bug in NIFI-1409 was a result of an exception being thrown when no columns were present in a result set returned by a query in the ExecuteSql processor. While NIFI-1409 is concerned with handling all such exceptions, this case is for the aforementioned exception.

The problem seems to be in JdbcCommon.createSchema():
https://github.com/apache/nifi/blob/nifi-0.4.1/nifi-nar-bundles/nifi-standard-bundle/nifi-standard-processors/src/main/java/org/apache/nifi/processors/standard/util/JdbcCommon.java#L130
This line asks for the table name for the first column, and when there are no columns, a SQLException is thrown.

The Avro docs suggest that no fields are necessary for the schema to be valid, so if there are no columns in the result set, a schema with no fields should be returned, rather than an exception being thrown.

Issue Links

• is related to: NIFI-1409 ExecuteSQL gives transfer error when SQLException occurs with no input flowfile