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From kant kodali <kanth...@gmail.com>
Subject Re: select count * doesnt seem to respect update mode in Kafka Structured Streaming?
Date Tue, 20 Mar 2018 00:27:26 GMT
Yes it indeed makes sense! Is there a way to get incremental counts when I
start from 0 and go through 10M records? perhaps count for every micro
batch or something?

On Mon, Mar 19, 2018 at 1:57 PM, Geoff Von Allmen <geoff@ibleducation.com>
wrote:

> Trigger does not mean report the current solution every 'trigger seconds'.
> It means it will attempt to fetch new data and process it no faster than
> trigger seconds intervals.
>
> If you're reading from the beginning and you've got 10M entries in kafka,
> it's likely pulling everything down then processing it completely and
> giving you an initial output. From here on out, it will check kafka every 1
> second for new data and process it, showing you only the updated rows. So
> the initial read will give you the entire output since there is nothing to
> be 'updating' from. If you add data to kafka now that the streaming job has
> completed it's first batch (and leave it running), it will then show you
> the new/updated rows since the last batch every 1 second (assuming it can
> fetch + process in that time span).
>
> If the combined fetch + processing time is > the trigger time, you will
> notice warnings that it is 'falling behind' (I forget the exact verbiage,
> but something to the effect of the calculation took XX time and is falling
> behind). In that case, it will immediately check kafka for new messages and
> begin processing the next batch (if new messages exist).
>
> Hope that makes sense -
>
>
> On Mon, Mar 19, 2018 at 13:36 kant kodali <kanth909@gmail.com> wrote:
>
>> Hi All,
>>
>> I have 10 million records in my Kafka and I am just trying to
>> spark.sql(select count(*) from kafka_view). I am reading from kafka and
>> writing to kafka.
>>
>> My writeStream is set to "update" mode and trigger interval of one
>> second (Trigger.ProcessingTime(1000)). I expect the counts to be printed
>> every second but looks like it would print after going through all 10M.
>> why?
>>
>> Also, it seems to take forever whereas Linux wc of 10M rows would take 30
>> seconds.
>>
>> Thanks!
>>
>

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