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Subject: Should collect() and count() be treated as data sinks?
From: Felix Neutatz <neutatz@googlemail.com>
To: dev@flink.apache.org
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Hi,

I have run the following program:

final ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();

List l = Arrays.asList(new Tuple1<Long>(1L));
TypeInformation t = TypeInfoParser.parse("Tuple1<Long>");
DataSet<Tuple1<Long>> data = env.fromCollection(l, t);

long value = data.count();
System.out.println(value);

env.execute("example");


Since there is no "real" data sink, I get the following:
Exception in thread "main" java.lang.RuntimeException: No data sinks have
been created yet. A program needs at least one sink that consumes data.
Examples are writing the data set or printing it.

In my opinion, we should handle count() and collect() like print().

What do you think?

Best regards,

Felix

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