Join attributes & policy

Join attributes to control and optimise performance

Stream join examples

streams join:
  expression: "sitevisits.customerId == webpage.adclicks.customerId"
  merge events: true
  left policy:
    time to live: 30 minutes
  right policy:
    delete on join: true

These attributes define how the join is performed with respect to the expression, how to create the emitted event structure etc.

Attributes schema

AttributeDescriptionData TypeRequired

expression

Simple join expression that evaluates two streams

String

merge events

Flag that either merge event attributes into a flattened event structure or places each event

Boolean Default: true

event type

User defined type of emitted event

String Default: left type - right type (i.e. typeA-typeB)

left / right join

See Join attribute section

Policy attribute Default

Policy Attributes

Fine grained control can be applied to how joins are handled through the use of the policy attribute.

This becomes relevant for large and fast event stream with respect to memory and processing overhead.

Default configuration

  1. delete on join is set to false and therefore will join events until the time to live setting is honoured.

  2. time to live is set for 60 minutes per stored event. This is refreshed every time a new event is received with the same join attribute value.

Attributes schema

AttributeDescriptionData TypeRequired

delete on join

Delete event from state management on a successful join

Boolean Default: false

time to live

Expire configuration for event stored within the state management system. Supported time units include nanoseconds, microseconds, milliseconds, seconds, hours and days

Formatted string Default: 60 minutes

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