@PublicEvolving public interface InputSelectable
IMPORTANT: This interface is a loose contract. The runtime may read multiple
records continuously before calling
nextSelection() again to determine whether
to change the input to be read. That is, it is not guaranteed that
will be called immediately after the operator has processed a record and the reading input
will be changed according to
InputSelection returned. This means that the operator
may receive some data that it does not currently want to process. Therefore, if an operator
needs a strict convention, it must cache the unexpected data itself and handle them correctly.
This interface also makes the following conventions:
1.The runtime must call
nextSelection() to determine the input to read the first record.
2.When the input being read reaches the end, the runtime must call
determine the next input to be read.
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