Pig treating map values as String causing ClassCastException in CONCAT
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Key: PIG-2045
URL: https://issues.apache.org/jira/browse/PIG-2045
Project: Pig
Issue Type: Bug
Components: impl
Affects Versions: 0.8.0, 0.9.0
Reporter: Vivek Padmanabhan
I have the below script ;
{code}
register mymapudf.jar;
a = load '4523893_1' as (f1);
a1 = foreach a generate org.vivek.udfs.mToMapUDF(f1);
a2 = foreach a1 generate mapout#'k1' as str1,mapout#'k3' as str2;
b = load '4523893_2' as (f1,f2);
c = join a2 by CONCAT(str1,str2) , b by CONCAT(f1,f2);
dump c;
{code}
The udf looks like below;
{code}
public class mToMapUDF extends EvalFunc<Map> {
@Override
public Map<String, Object> exec(Tuple arg0) throws IOException {
Map <String,Object> myMapTResult = new HashMap<String,
Object>();
myMapTResult.put("k1", "SomeString");
myMapTResult.put("k3", "SomeOtherString");
return myMapTResult;
}
@Override
public Schema outputSchema(Schema input) {
// TODO Auto-generated method stub
return new Schema(new
Schema.FieldSchema("mapout",DataType.MAP));
}
}
{code}
The script fails with exception ;
java.lang.ClassCastException: java.lang.String cannot be cast to
org.apache.pig.data.DataByteArray
at org.apache.pig.builtin.CONCAT.exec(CONCAT.java:51)
The values of the map output, ie str1 and str2, is autmomatically treated as
String by Pig and this causes the ClassCast exception when it is used in
subsequent udfs.
Since there are no explicit casting done nor any types defined, Pig should
treat the values as the default bytearray. This issue is also observed in 0.9
The workaround in this case is to cast explicitly to chararray all keys
involved in join.
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