EVER

Window that retains the latest events based on a given unique keys. When a new event arrives with the same key it replaces the one that exist in the window.

caution

This function is not recommended if the maximum number of unique attributes are undefined, as there is a risk of system going out to memory.

Syntax

    WINDOW UNIQUE:EVER(<INT|LONG|FLOAT|BOOL|DOUBLE|STRING> unique.key)
    WINDOW UNIQUE:EVER(<INT|LONG|FLOAT|BOOL|DOUBLE|STRING> unique.key, <INT|LONG|FLOAT|BOOL|DOUBLE|STRING> ...)

Query Parameters

Name	Description	Default Value	Possible Data Types	Optional	Dynamic
unique.key	The attribute used to checked for uniqueness.		INT LONG FLOAT BOOL DOUBLE STRING	No	Yes

Example 1

    CREATE STREAM LoginEvents (timestamp long, ip string);

    INSERT events INTO UniqueIps
    SELECT count(ip) AS ipCount
    FROM LoginEvents WINDOW UNIQUE:EVER(ip)    
    

This query collects all unique events based on the ip attribute by retaining the latest unique events from the LoginEvents stream. Then the query counts the unique ips arrived so far and outputs the ipCount via the UniqueIps stream.

Example 2

    CREATE STREAM DriverChangeStream (trainID string, driver string);

    INSERT expired events INTO PreviousDriverChangeStream;
    SELECT trainID, driver
    FROM DriverChangeStream WINDOW UNIQUE:EVER(trainID)

Query collects all unique events based on the trainID attribute by retaining the latest unique events from the DriverChangeStream. The query outputs the previous unique event stored in the window as the expired events are emitted via PreviousDriverChangeStream.

Example 3

    CREATE STREAM StockStream (symbol string, price float);
    CREATE SINK STREAM PriceRequestStream(symbol string);

    INSERT events INTO PriceResponseStream;
    SELECT s.symbol AS symbol, s.price AS price
    FROM StockStream WINDOW UNIQUE:EVER(symbol) AS s JOIN PriceRequestStream AS p
    ON s.symbol == p.symbol

Query stores the last unique event for each symbol attribute of StockStream, and joins them with events arriving on the PriceRequestStream for equal symbol attributes to fetch the latest price for each requested symbol and output it to PriceResponseStream.