Jumping Windows

Jumping Windows retain data for a specified interval of time or for a specified number of rows and delete all retained rows when the specified interval of time expires, or the specified number of rows is exceeded.

Jumping Windows are specified by the KEEP EVERY clause. A retention policy can be directly specified on a Window and indirectly specified on Windows and Delta Streams (using unnamed windows).

Note: Retention cannot be specified directly or indirectly on a Stream.

Tuples are the sets of data that are retained in the Window. Insert tuples affect retention, yet the arrival of update and/or delete tuples does not trigger the retention mechanism.

Example

The example creates a schema named TradesSchema and applies that schema to the input window Trades.

CREATE SCHEMA TradesSchema (
    Id     integer,
    Symbol string,
    Price  float,
    Volume integer
) ;

CREATE INPUT WINDOW Trades
    SCHEMA TradesSchema
    PRIMARY  KEY (Id) ;

The example then creates various types of Jumping Windows.

This creates a Jumping Window named Every5Rows from the source stream Trades. This window retains a maximum of five rows then deletes all five retained rows on the arrival of a new row.

CREATE OUTPUT WINDOW Every5Rows
PRIMARY KEY DEDUCED
KEEP EVERY 5 ROWS
AS SELECT * FROM Trades ;

This creates a Jumping Window named Every5Seconds from the source stream Trades. This window retains rows for a maximum of five seconds then deletes all retained rows when the time interval expires.

CREATE OUTPUT WINDOW Every5Seconds
PRIMARY KEY DEDUCED
KEEP EVERY 5 SECONDS
AS SELECT * FROM Trades ;

This creates an unnamed Jumping Window from the source stream Trades. This window retains a maximum of five rows for each unique value of Symbol then deletes all five retained rows upon the arrival of a sixth row with the same Symbol value.

CREATE OUTPUT WINDOW Every5RowsPerSymbol
PRIMARY KEY DEDUCED
AS SELECT * FROM Trades KEEP EVERY 5 ROWS PER(Symbol)

The example concludes by attaching the XML Input Adapter to Trades to process the incoming stream data.

ATTACH INPUT ADAPTER xmlInConn1
    TYPE xml_in
    TO Trades
    PROPERTIES
        blockSize=1,
        dir='../exampledata',
        file='Trades.xml',
        filePattern='*.xml',
        safeOps=false,
        skipDels=false ;