Open topic with navigation

TIBCO BusinessEvents® Enterprise Edition 6.3.1

# Stream Policy

The stream policy (also known as a window policy) is used for continuous queries only. It determines what kind of window is used: a time window, sliding window, or tumbling window.

See Working With Sliding Tumbling and Time Windows and examples following: Sliding Window Examples (Cache Queries), Tumbling Window Examples (Cache Queries), and Time Window Examples (Cache Queries).

Note that continuous queries that use an implicit window do not have a stream policy. See Working With Implicit Windows.

The value of `long literal` specifies the size of the window. When used for a time window, the value refers to a time unit specified by `time unit`. The time unit can be specified in milliseconds, seconds, minutes, hours or days. For example: `maintain last 5 minutes` defines a time window of five minutes.

For sliding and tumbling windows, the number refers to a number of entities.

## Using Clause

When the query specifies time units, you can specify a start time by including a `using` clause. The expression could refer to a timestamp property in the entity, for example. If the `using` clause is absent, the start time is the moment the entity enters the window.

## Where Clause

The optional `where` clause is used as a pre-filter (a filter on results that enter the window). It eliminates entities that are not useful for the query, optimizing performance.

## By Clause

Maintaining a single window (like a sliding window) over all the events in the window may not be what you need for a query. The (optional) `by` clause allows you to do aggregations within the window. In this regard, the `by` clause is similar to the `group by` clause.

For example, instead of a single window of size 50 that contains all the entities, you can maintain a window of size 50 for each combination of values for the fields in the `by` section:

    select car.id, car.color from "CarEvent" {policy: maintain last 50 sliding  where type = "Sedan" by country, state, city} car;

See Explicit Window Example (Cache Query) for a detailed discussion of an example that uses a stream policy. See Time Window Examples (Cache Queries) for more examples.

Did you find this helpful?

YesNo
Great!
Thanks for taking the time to give us some feedback.
Sorry about that

Why wasn't this helpful? (check all that apply)

Could not find what I was looking for
Instructions confusing or unclear
Instructions did not work

Want to tell us more?

Please select at least one option or provide details about the issue!!

Error occurred while submitting feedback.

Error2 occurred while submitting feedback.

TIBCO BusinessEvents® Enterprise Edition

Copyright © 2004-2024. Cloud Software Group, Inc. All Rights Reserved.