Query Pipeline Stages
A query pipeline is made up of a series of query stages that process incoming search queries.
A pipeline stage definition associates a unique ID with a set of properties. These definitions are registered with the Fusion API service and stored in ZooKeeper for re-use across pipelines and search applications.
Fusion includes a number of specialized query stages as well as a JavaScript stage that allows advanced processing via a JavaScript program.
Configuring query pipeline stages
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In the Fusion UI, the Query Workbench provides an environment for configuring the stages in a query pipeline.
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The Query Stages API is used to create, list, update, or delete query stages using JSON. See also the Query Pipelines API.
Asynchronous query pipeline processing
Query pipeline processing performance can be improved by enabling asynchronous processing for certain stages that make requests to secondary collections, external databases, and so on. The following stages support asynchronous processing:
This feature uses the fork-and-join model, where any of the stages above can create a fork on the pipeline. The parallel processes are joined again using the Merge Async Results stage at a later point in the pipeline.
Conditional query processing
Query Pipeline stages are used to modify Request objects
and Response objects. Each stage can include a conditional JavaScript expression (the condition property in its configuration) that can access these objects.
For example, this condition first checks that the property fusion-user-name is specified in the Request object, then checks for a particular value:
request.hasParam("fusion-user-name") && request.getFirstParam("fusion-user-name").equals("SuperUser");