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Re: [flink-cep] Flick CEP support for the group By operator


Yes, sure. Just use CEP on top of KeyedStream. Take a look at `keyBy`:


On 23 Nov 2018, at 16:04, Spico Florin <spicoflorin@xxxxxxxxx> wrote:


I'm using Flink 1.4.2 and I would like to use a group by operator based on value of my event stream. The functionality that I would like to achieve is similar to the following Esper EPL

select symbol, tickDataFeed, median(volume) 
from StockTickEvent.win:time(30 sec) 
group by symbol, tickDataFeed

So, does the Flick CEP  support such a group by functionality? 

If yes what is syntax?

I look forward for your answers.

Best regards,


"You can list more then one _expression_ in the group by clause to nest groups. Once the sets are established with group by the aggregation functions are applied. This statement posts the median volume for all stock tick events in the last 30 seconds per symbol and tick data feed. Esper posts one event for each group to statement listeners:

In the statement above the event properties in the select list (symbol, tickDataFeed) are also listed in the group by clause. The statement thus follows the SQL standard which prescribes that non-aggregated event properties in the select list must match the group by columns."