Hi Reuven,

What about watermark? Should Flatten emit the min watermark of all input
data streams? If that is the case, one late tuple can become early after
Flatten, right? Will that cause any problem?


On Mon, Mar 12, 2018 at 4:09 PM, Reuven Lax <re...@google.com> wrote:

> No, I don't think it makes sense for the Flatten operator to cache
> element.
> On Mon, Mar 12, 2018 at 11:55 AM Shen Li <cs.she...@gmail.com> wrote:
>> If multiple inputs of Flatten proceed at different speeds, should the
>> Flatten operator cache tuples before emitting output watermarks? This can
>> prevent a late tuple from becoming early. But if the watermark gap (i.e.,
>> cache size) becomes too large among inputs, can the application tell
>> Beam/runner to emit output watermark anyway and consider slow input tuples
>> as late?
>> Thanks,
>> Shen

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