LiveView Query Input Adapter

Name: Use this required field to specify or change the name of this instance of this component, which must be unique in the current EventFlow module. The name must contain only alphabetic characters, numbers, and underscores, and no hyphens or other special characters. The first character must be alphabetic or an underscore.

Adapter: A read-only field that shows the formal name of the adapter.

Class name: Shows the fully qualified class name that implements the functionality of this adapter. If you need to reference this class name elsewhere in your application, you can right-click this field and select Copy from the context menu to place the full class name in the system clipboard.

Start with application: If this field is set to Yes (default) or to a module parameter that evaluates to true, this instance of this adapter starts as part of the JVM engine that runs this EventFlow module. If this field is set to No or to a module parameter that evaluates to false, the adapter instance is loaded with the engine, but does not start until you send an sbadmin resume command, or until you start the component with StreamBase Manager.

Enable Error Output Port: Select this check box to add an Error Port to this component. In the EventFlow canvas, the Error Port shows as a red output port, always the last port for the component. See Using Error Ports to learn about Error Ports.

Description: Optionally enter text to briefly describe the component's purpose and function. In the EventFlow canvas, you can see the description by pressing Ctrl while the component's tooltip is displayed.

This section describes the properties on the Adapter Properties tab in the Properties view for the LiveView Query adapter.

This tab allows you to configure one or more ad hoc queries that are to be registered each time the adapter connects to the specified LiveView server. If no Query Input Port is specified for this adapter instance, then the queries listed in this tab are the only ones this adapter instance runs. Note that these are only applied to a table named in the Target table name property.

Each query line in this tab's grid is automatically assigned an ad hoc query name of the form InitialQuerynn, where nn is an integer starting with zero. The query in the first line is assigned InitialQuery0, the second line gets InitialQuery1, and so on. Use these query names to identify individual queries in the adapter's output streams. The query name also allows you to identify a query to be unregistered by means of a tuple sent to the adapter's input port.

The tab's grid has two columns, each representing part of a LiveView query string. The Select column specifies the projection expression for the query. For simple, non-aggregate queries, this column typically contains a single asterisk, which specifies selecting all fields in the table. For dynamic aggregation queries, the expression in this column defines the aggregate functions and values to use for this query. For example, a Select column might contain: avg(lastSoldPrice) as AvgSoldPrice, category 

The Query column specifies the predicate expression for each query. This predicate can include a time window specified with between and, and can include order by, group by, and limit where appropriate.

Use the Edit Schema tab to specify the schema of the LiveView table specified in the Target Table Name field of Adapter Properties tab. This is the table that this adapter instance is to issue queries against. The schema defined here is not used for queries that come via the TableName field of the Query Input Port or that are dynamic aggregation queries, those use a generic JSON format for their output.

For general instructions on using the Edit Schema tab, see Defining Input Streams.

Use the Concurrency tab to specify parallel regions for this instance of this component, or multiplicity options, or both. The Concurrency tab settings are described in Concurrency Options, and dispatch styles are described in Dispatch Styles.

The optional QueryIn port can be used to register new ad hoc queries sent to the LiveView server at runtime, and to delete (unregister) queries. This port is added by selecting the Query Input Port check box on the Adapter Properties tab.

The port's schema is shown in the following table. When sending a new query to be registered, use all five fields. When sending a tuple to unregister an existing query, use only the first and last fields.

The LiveView Query adapter has one output status port and up to two query output ports.

The status port has the fields shown in the following table:

The LiveView Query adapter has a QueryOut output port, on which tuples are emitted that describe the results of all registered non-aggregate queries. The schema of this output has six fields, two of which have the tuple data type. The schemas for the two tuple fields are configured in the Edit Schema tab.

The LiveView Query adapter has a separate output port, JSONQueryOut, to report the results from queries for which the result schema is not known. This includes dynamic aggregation queries and queries that result from using the TableName input. In such queries, the result itself defines the schema. In response, the variable output schema from such queries are represented in a JSON string. You can use StreamBase expression language functions, such as parsejson() to extract the tuple values from these JSON strings.

Add an instance of the adapter to a new EventFlow application with the following steps: