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https://issues.apache.org/jira/browse/PIG-1843?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12990886#comment-12990886
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Daniel Dai commented on PIG-1843:
---------------------------------
The problem happens when we have nested UDF:
1. Inner UDF does not define complete outputSchema
2. Outer UDF does not define getArgToFuncMapping
3. outputSchema in outer UDF uses inner schema to infer alias
> NPE in schema generation
> ------------------------
>
> Key: PIG-1843
> URL: https://issues.apache.org/jira/browse/PIG-1843
> Project: Pig
> Issue Type: Bug
> Affects Versions: 0.8.0
> Reporter: Daniel Dai
> Assignee: Daniel Dai
> Fix For: 0.8.0, 0.9.0
>
>
> Hit NPE in following script:
> {code}
> a = load 'table_testBagDereferenceInMiddle2' as (a0:chararray);
> b = foreach a generate MapGenerate(STRSPLIT(a0).$0));
> {code}
> {code}
> public class MapGenerate extends EvalFunc<Map> {
> @Override
> public Map exec(Tuple input) throws IOException {
> Map m = new HashMap();
> m.put("key", new Integer(input.size()));
> return m;
> }
>
> @Override
> public Schema outputSchema(Schema input) {
> return new Schema(new Schema.FieldSchema(getSchemaName("parselong",
> input), DataType.MAP));
> }
> }
> {code}
> Error message:
> Caused by: java.lang.NullPointerException
> at org.apache.pig.EvalFunc.getSchemaName(EvalFunc.java:76)
> at string.PARSELONG.outputSchema(PARSELONG.java:63)
> at
> org.apache.pig.newplan.logical.expression.UserFuncExpression.getFieldSchema(UserFuncExpression.java:154)
> at
> org.apache.pig.newplan.logical.optimizer.FieldSchemaResetter.execute(SchemaResetter.java:192)
> at
> org.apache.pig.newplan.logical.expression.AllSameExpressionVisitor.visit(AllSameExpressionVisitor.java:143)
> at
> org.apache.pig.newplan.logical.expression.UserFuncExpression.accept(UserFuncExpression.java:71)
> at
> org.apache.pig.newplan.ReverseDependencyOrderWalker.walk(ReverseDependencyOrderWalker.java:70)
> at org.apache.pig.newplan.PlanVisitor.visit(PlanVisitor.java:50)
> at
> org.apache.pig.newplan.logical.optimizer.SchemaResetter.visit(SchemaResetter.java:104)
> at
> org.apache.pig.newplan.logical.relational.LOGenerate.accept(LOGenerate.java:240)
> at
> org.apache.pig.newplan.DependencyOrderWalker.walk(DependencyOrderWalker.java:75)
> at
> org.apache.pig.newplan.logical.optimizer.SchemaResetter.visit(SchemaResetter.java:93)
> at
> org.apache.pig.newplan.logical.relational.LOForEach.accept(LOForEach.java:73)
> at
> org.apache.pig.newplan.DependencyOrderWalker.walk(DependencyOrderWalker.java:75)
> at org.apache.pig.newplan.PlanVisitor.visit(PlanVisitor.java:50)
> at
> org.apache.pig.backend.hadoop.executionengine.HExecutionEngine.compile(HExecutionEngine.java:279)
> at org.apache.pig.PigServer.compilePp(PigServer.java:1480)
> at org.apache.pig.PigServer.explain(PigServer.java:1042)
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