Page Comparison

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1. External Calls (Not supported in the current version)

   Instead of directly returning or inserting the results to the output stream, Siddhi allows users to send the event to an external function and get the results.

   from <stream>
   insert into <stream-name>
   call <function-name>”(“<parameters>”)” ( {<attribute-name>}| ‘*’)

   Example,
   For the StockStream events having symbol=’IBM’, Siddhi will query StockTable of myStockDb database for all the events having symbol=’IBM’ and output them via IBMStream with attributes symbol, price and volume.

   from StockStream[symbol=’IBM’]
   insert into IBMStream
        call sql(myStockDb,
                  “select symbol, price, vol from StockTable where
                  symbol==${StockStream.symbol})”,
                 “{symbol string, price int, volume float}”);

    

2. Recursive (nested) queries are not supported in the current version

   This gives the events having average price over 50 events per symbol, having price >= 20 and symbol == ‘IBM’ from all incoming events of StockExchangeStream

   from (from StockExchangeStream[ price >= 20]#window.length(50)
   return symbol, avg(price) as avgPrice
            group by symbol) [symbol=="IBM"]
   insert into IBMStockQuote symbol, avgPrice
   
   

3. Siddhi

   will

   does not support joining

   multiple streams

   three or more streams in a single query .

   from RfidEvent#window.time(3000) as rfid
           left outer join ProductName#window.length(100) as refprod
                  on rfid.productId = refprod.prodId
          left outer join LocationDescription#window.length(200) as refdesc
                 on rfid.location = refdesc.locId
   insert into JoinStream *

   As a workaround user can first join two stream and then join the resulting stream with the third stream.