Filters

Filters provide a way of filtering input stream events based on a specified condition. It accepts any type of condition including a combination of functions and/or attributes that produces a Boolean result. Filters allow events to passthrough if the condition results in true, and drops if it results in a false.

For more filtering examples, refer to Data Cleaning Examples.

Purpose

Filter helps to select the events that are relevant for the processing and omit the ones that are not.

Syntax

Filter conditions should be defined in square brackets ([]) next to the input stream as shown below.

INSERT INTO <output stream>
SELECT <attribute name>, <attribute name>, ...
FROM <input stream>[<filter condition>] ;

Example

Query to filter TempStream stream events, having roomNo within the range of 100-210 and temperature greater than 40 degrees, and insert them into HighTempStream stream.

INSERT INTO HighTempStream
SELECT roomNo, temp
FROM TempStream[(roomNo >= 100 and roomNo < 210) and temp > 40];