Joins

An interval join is available in Event Processing.

Interval join

An interval join is used to merge two event streams based on a join condition that matches events within a time period.

Output properties

Event Processing 1.1.3 icon You can manage the properties that come from this node to suit your requirements. When the properties from the events of the two input nodes are merged, you might have to resolve naming conflicts by renaming or removing properties.

The merge of properties is done both at top-level and at nested levels. If both input nodes contain a complex object property with the same name, all the properties from both inputs are merged, and you need to resolve the naming conflicts by renaming or removing properties.

Adding an interval join node

To add an interval join, complete the following steps:

  1. Ensure that a stream of events is available, from an Event Source node or from the output of any previously configured node.
  2. In the Palette, under Joins, drag the Interval join node into the canvas.
  3. Connect the node to two event sources by separately dragging the Output Port from each source node into the Input Port of this node.
  4. Hover over the node and click Edit icon Edit to configure the node.

The Configure Interval join window is displayed.

Configuring an interval join node

To configure an interval join, complete the following steps:

Details

In the Details section, enter a name for your node. The output stream of events from this node will be referred with the name you entered.

Join condition

To define your join condition, on the Join condition section, in the Define events text box, enter your expression.

Examples:

  • Simple expression:

     source1.example_property = source2.example_property

  • Event Processing 1.1.3 icon Expression with a complex object property:

    source1.example_property.nested_object_property.leaf_property = source2.leaf_property

  • Event Processing 1.1.4 icon Expressions with array properties:

     - ARRAY_CONTAINS(source1.example_property.nested_object_property.leaf_array_property, source2.leaf_property)
 - ELEMENT(source1.array_property) = source2.leaf_property

  • Event Processing 1.1.8 icon Expressions with complex array properties:

     - ELEMENT(source1.example_array_property) = ELEMENT(source2.example_array_of_array_of_object_property[1][1].stringArray)
 - ARRAY_CONTAINS(source1.example_array_of_array_of_object_property[1][1].floatArray, source2.example_array_of_object_property[1].floatArray)
 - CARDINALITY(source1.example_array_of_array_property[1]) = CARDINALITY(source2.example_array_property)

Alternatively, to use the assistant to create your expression, complete the following steps:

  1. Click the Assistant drop-down menu to open the assistant.
  2. In the Property from [name of the first event source] drop-down menu, select the property that you want to match.
  3. In the Property from [name of the second event source] drop-down menu, select a property to match the one chosen in step 2.
  4. Click Add to expression to insert the expression into the text-box.

Note: Ensure that the property you choose for both sides of your expression has the same data type.

Note: The Assistant drop-down menu does not support array properties. However, you can manually write the expressions by selecting the property from the list that appears when you press Ctrl+Space in the Expression field.

Event Processing 1.1.9 icon Note: A tree view of the event structure is available. To view all the input properties of the current node, click View input properties in the upper-right corner of the pane.

Time window condition

To define the time window condition, complete the following steps:

  1. In the Event to detect drop-down menu, select the property of the event you are interested in.
  2. In the Event to set the time window drop-down menu, select the property of an event used to define the time window.
  3. In the Offset from event to start the time window field, input an integer value and select the corresponding time unit. Then input another integer in the Offset from event to end the time window field to define the duration of the time window.

Note: Ensure that the end-time of the time window is later than the start-time.

Output properties

You can manage the properties that come from this node to suit your requirements.

Rename a property

To rename a property, complete the following steps:

  1. Hover over the property name and click the Edit icon rename icon.
  2. In the text-box, enter a new name for your property.
  3. Click outside the text-box or press Enter on your keyboard to rename the property.

Properties to remove

To remove a property from being displayed in the output, click the Remove property icon remove icon.

Note: Take extreme care in removing an event time property. By keeping an event time property, you can propagate the event time to downstream nodes on the canvas. The event time property is necessary for time-based calculations in nodes, such as aggregate or another interval join.

Add a removed property

To add a property that was previously removed, complete the following steps:

  1. Go to the Properties to remove table that lists the removed properties.
  2. In the row of the property that you want to restore, click the Add icon add icon.

After you have set up the interval join node, click Configure.

A green checkbox green checkbox appears on the interval join node if the interval join node is configured correctly. If there is any error in your configuration, a red checkbox red checkbox appears.

User actions are saved automatically. For save status updates, see the canvas header.