In TQL, a query is any operations on the model instance data (or model data), which includes filtering, joining, and manipulations. Model instances are incarnations of the Models (or model definitions) through instantiation. The TQLEngine stores the latest version of the model instance data, which is accessible to TQL Queries. See data storage for more details.
There is a special type of query which allows you to show or list the model definitions themselves. See /wiki/spaces/TQLDocs/pages/1179668 for details.
Like conventional queries, TQL queries perform CRUD operations on data. but unlike conventional database queries, TQL queries are:
(1) Current. The TQLEngine maintains the latest versions of any attribute values and attribute known values. TQL queries always return those latest versions.
(2) Model-driven. Since the model definitions define the structure of the model data, the TQLEngine constructs the database queries based on the model definition to retrieve requested data or perform other CRUD operations. The model definition is NOT data schema. Model instance data are saved in schemaless key value pairs.
(3) Actionable. Modifications of model data via TQL queries, if involving actionable attributes, can result in activation of actions, some of which may execute device actuations.
in the mqp file, you define query end points. Query end points are channels to communicate through the TQLFacet instance with the TQLEngine.
Usually studio automatically generate the mqp file, which define two query end points:
http:// - for all queries except subscription. Sync (timeout?)
ws:// - subscription is always sent and received from the ws. Async
Describe the common structure of a query end point.
When a project is deployed onto a TQL Engine, it always creates two end points
Queries are sent to end points as payload of a message.
What about the Query End Points?
When to use queries, what are the different ways
(1) from the app (client to TQLEngine) - external (needs query end point), - return will be sent as message back to client.
(2) from model facet, invoke - internal (the return will be the output of the invoke). - query itself become part of the model action.
What can go inside a query
Save, update, delete, deleteAll, Find. Create, SetResponseData, For
Find can have constraints
FacetScript, JavaScript
Macro
Does query only change value, not known value (true)
What is the common structure of a query
What are the most commonly used types of queries
Instantiation query (create), or save
Subscription query (save)
Find query, joint query
Update (update, save)
Macro
Show query