How do I convert a tuple with a wide schema to a narrower subset schema?
Article ID: KB0076146
Updated On:
| Products | Versions |
|---|---|
| TIBCO Streaming | 7 |
Description
How do I convert a tuple with a wide schema to a narrower subset schema?
And how do I do it in such a way that I don't have to explicitly remove all the fields that aren't in Little schema one by one?
I have LittleSchema (int a, int b, int c) and I have BigSchema (int a, int b, int c, int d, int e). That is, BigSchema is a subtype of LittleSchema.
I want to take in BigSchema tuples from input stream BigSchemaIn, convert each BigSchema tuple to a LittleSchema tuple by omitting all the fields not in LittleSchema, and sending the resulting tuples to output stream LittleSchemaOut.
And how do I do it in such a way that I don't have to explicitly remove all the fields that aren't in Little schema one by one?
I have LittleSchema (int a, int b, int c) and I have BigSchema (int a, int b, int c, int d, int e). That is, BigSchema is a subtype of LittleSchema.
I want to take in BigSchema tuples from input stream BigSchemaIn, convert each BigSchema tuple to a LittleSchema tuple by omitting all the fields not in LittleSchema, and sending the resulting tuples to output stream LittleSchemaOut.
Issue/Introduction
How do I convert a tuple with a wide schema to a narrower subset schema?
Resolution
Use new_tuple_subset_loose() in a Map operator to create a tuple field with the target schema, then in a second Map operator promote all the sub-tuple fields back to the top level fields in the stream.
The Map expression is (for example):
Add, smallTuple, new_tuple_subset_loose(LittleSchema(), BigSchemaIn.* AS *)
To promote, set the Map to NOT include any fields from the input stream and use expression:
Add, *, smallTuple.*
The Map expression is (for example):
Add, smallTuple, new_tuple_subset_loose(LittleSchema(), BigSchemaIn.* AS *)
To promote, set the Map to NOT include any fields from the input stream and use expression:
Add, *, smallTuple.*
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