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Query Set And Batch

This abstract layer helps to manage a group of queries instead of working with each query independently. To initialize a new QuerySet instance, call the following method from the Connection instance:

let querySet = connection.querySet();

Supported methods​

retrieve​

Only retrieves initial data and immediately removes the query from the Event Delivery Service after the response:

querySet.retrieve("SELECT * FROM <YOUR-COLLECTION> WHERE key=<YOUR-KEY>", (event) => {
    console.log(`Message event: `, event);
})

retrieveAndSubscribe​

Retrieves initial data and subscribes to changes in the query:

querySet.retrieveAndSubscribe("SELECT * FROM <YOUR-COLLECTION> WHERE key=<YOUR-KEY>", (event) => {
    console.log(`Message event: `, event);
})

subscribe​

Only subscribes to changes in the query:

querySet.subscribe("SELECT * FROM <YOUR-COLLECTION> WHERE key=<YOUR-KEY>", (event) => {
    console.log(`Message event: `, event);
})

unubscribe​

Removes a subscription if the query was subscribed in the QuerySet. This applies only to the retrieveAndSubscribe and subscribe methods:

querySet.unsubscribe("SELECT * FROM <YOUR-COLLECTION> WHERE key=<YOUR-KEY>");

batch​

To make requests to the Event Delivery Service more efficient, it is possible to join them into one WebSocket/SSE message. This returns a QueryBatch instance, which has the same methods (retrieve, retrieveAndSubscribe, subscribe, unsubscribe) as QuerySet. The final method should beassemble(), which builds and sends the message:

let queryBatch = querySet.batch();
queryBatch
    .retrieve("SELECT * FROM <YOUR-COLLECTION> WHERE key=<YOUR-KEY>", (event) => {
       console.log(`Message event: `, event);
    })
    .retrieveAndSubscribe("SELECT * FROM <YOUR-COLLECTION> WHERE key=<YOUR-KEY>", (event) => {
       console.log(`Message event: `, event);
    })
    .subscribe("SELECT * FROM <YOUR-COLLECTION> WHERE key=<YOUR-KEY>", (event) => {
       console.log(`Message event: `, event);
    })
    .unsubscribe("SELECT * FROM <YOUR-COLLECTION> WHERE key=<YOUR-KEY>")
    .assemble();

unubscribeAll​

Removes all subscriptions in the QuerySet:

querySet.unsubscribeAll();