Delta Streams

Delta streams are stateless elements that can understand all opcodes.

You can use a delta stream anywhere you use a computation, filter, or union, but do not need to maintain a state. A delta stream performs these operations more efficiently than a window because it keeps no state, thereby reducing memory use and increasing speed.

Example

This example creates a delta stream named DeltaTrades that incorporates the getrowid and now functions.

CREATE LOCAL DELTA STREAM DeltaTrades
	SCHEMA (
		RowId long, 
		Symbol STRING, 
		Ts bigdatetime, 
		Price MONEY(2), 
		Volume INTEGER, 
		ProcessDate bigdatetime )
	PRIMARY KEY (Ts)
AS SELECT  getrowid ( TradesWindow) RowId, 
		TradesWindow.Symbol,
 		TradesWindow.Ts Ts, 
 		TradesWindow.Price, 
 		TradesWindow.Volume, 
 		now() ProcessDate
	FROM TradesWindow 

CREATE OUTPUT WINDOW TradesOut 
	PRIMARY KEY DEDUCED 
AS SELECT * FROM DeltaTrades ;