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https://issues.apache.org/jira/browse/PIG-2375?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13172981#comment-13172981
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Prashant Kommireddi commented on PIG-2375:
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On having thought some more, when getArgToFuncMapping() is used the check is
made based on this to invoke an overriding EvalFunc. It does not really make a
lot of sense to use outputSchema(Schema inputSchema) to verify input schema
once again.
The role of outputSchema (as the name suggests) should be to specify the output
schema for the UDF, and NOT necessarily to verify the input schema. Though for
a new user or writer of Pig UDFs this might not seem obvious when overriding
UDFs.
To summarize:
1. When UDF is not overriden, it is ok to use outputSchema to verify input
schema.
2. When UDF is Overriden, it does not make sense to use outputSchema to verify
input schema. This is because getArgToFuncMapping already finds a matching spec
based on the input schema.
> Incorrect outputSchema is invoked when overloading UDF in 0.9.1
> ---------------------------------------------------------------
>
> Key: PIG-2375
> URL: https://issues.apache.org/jira/browse/PIG-2375
> Project: Pig
> Issue Type: Bug
> Affects Versions: 0.9.1
> Reporter: Prashant Kommireddi
> Assignee: Prashant Kommireddi
> Fix For: 0.9.1
>
> Attachments: LogFieldValue.java, LogFieldValues.java
>
>
> When overloading a UDF with getArgToFuncMapping() the parent/root UDF
> outputSchema() is being called.
> {code}
> @Override
> public List<FuncSpec> getArgToFuncMapping() throws FrontendException {
> List<FuncSpec> funcList = new ArrayList<FuncSpec>();
> Schema s = new Schema();
> s.add(new Schema.FieldSchema(null, DataType.TUPLE));
> s.add(new Schema.FieldSchema(null, DataType.CHARARRAY));
> funcList.add(new FuncSpec(this.getClass().getName(), s));
> Schema s1 = new Schema();
> s1.add(new Schema.FieldSchema(null, DataType.TUPLE));
> s1.add(new Schema.FieldSchema(null, DataType.TUPLE));
> funcList.add(new FuncSpec(LogFieldValues.class.getName(), s1));
> return funcList;
> }
> {code}
> In the above function, "LogFieldValues" is used when the input is (tuple,
> tuple) but the outputSchema() is invoked from the root UDF.
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