Aljoscha Krettek created FLINK-17074:
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Summary: Deprecate DataStream.keyBy() that use tuple/expression
keys
Key: FLINK-17074
URL: https://issues.apache.org/jira/browse/FLINK-17074
Project: Flink
Issue Type: Improvement
Components: API / DataStream
Environment: Currently you can either specify a {{KeySelector}}, tuple
positions, and expression keys? I think {{KeySelectors}} are strictly superior
and with lambdas (or function references) quite easy to use. Tuple/expression
keys use reflection underneath to do the field accesses, so performance is
strictly worse. Also, when using a {{KeySelector}} you will have a meaningful
key type {{KEY}} in your operations while for tuple/expression keys the key
type is simply {{Tuple}}.
Tuple/expression keys were introduced before Java got support for lambdas in
Java 8 and before we added the Table API. Nowadays, using a lambda is little
more typing than using an expression key but is (possibly) faster and more type
safe. The Table API should be used for these more expression-based/relational
use cases.
Reporter: Aljoscha Krettek
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