[PIG-851] Map type used as return type in UDFs not recognized at all times

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.3.0
• Fix Version/s: 0.4.0
• Component/s: impl
• Patch Info: Patch Available
• Assignee: Jeff Zhang
• Reporter: Santhosh Muthur Srinivasan
• Created: 16/Jun/09 01:15
• Updated: 24/Mar/10 22:13
• Resolved: 14/Jul/09 03:15

Description

When an UDF returns a map and the outputSchema method is not overridden, Pig does not figure out the data type. As a result, the type is set to unknown resulting in run time failure. An example script and UDF follow

public class mapUDF extends EvalFunc<Map<Object, Object>> {

    @Override
    public Map<Object, Object> exec(Tuple input) throws IOException {
            return new HashMap<Object, Object>();
    }

//Note that the outputSchema method is commented out

/*
    @Override
    public Schema outputSchema(Schema input) {
        try {
            return new Schema(new Schema.FieldSchema(null, null, DataType.MAP));
        } catch (FrontendException e) {
            return null;
        }
    }
*/

grunt> a = load 'student_tab.data';           
grunt> b = foreach a generate EXPLODE(1);
grunt> describe b;

b: {Unknown}

grunt> dump b;

2009-06-15 17:59:01,776 [main] INFO  org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.MapReduceLauncher - Failed!

2009-06-15 17:59:01,781 [main] ERROR org.apache.pig.tools.grunt.Grunt - ERROR 2080: Foreach currently does not handle type Unknown