Realtime data streaming

You can use the SurrealDB SDK to create live queries that listen for changes in the database and automatically update your application when changes occur. This feature is useful for building real-time applications that need to respond to changes in the database.

.ListenLive<T>()

Listen responses from an existing live query.

Method Syntax
db.ListenLive<T>(queryUuid)

Arguments

Example usage

await using var liveQuery = db.ListenLive<Person>(queryUuid);

// Consume the live query...

You can then consume the live query using either an IAsyncEnumerable or an Observable.

Using an IAsyncEnumerable

:::note NOTE: This will block the current thread until the query is killed. :::

Option 1: Consume the live query via an IAsyncEnumerable
await foreach (var response in liveQuery)
{
    // Either an Open, Create, Update, Delete or Close notification...

    if (response is SurrealDbLiveQueryOpenResponse)
    {
        // Do something...
    }
    if (response is SurrealDbLiveQueryCreateResponse<Person> create)
    {
        // Use the `Result` record
    }
    if (response is SurrealDbLiveQueryUpdateResponse<Person> update)
    {
        // Use the `Result` record
    }
    if (response is SurrealDbLiveQueryDeleteResponse<Person> delete)
    {
        // Use the `Result` record
    }
    if (response is SurrealDbLiveQueryCloseResponse)
    {
        // Do something...
    }
}

Using an Observable

Option 2: Consume the live query via an Observable
liveQuery
    .ToObservable()
    .Subscribe((response) => 
    {
        // Either an Open, Create, Update, Delete or Close notification...

        if (response is SurrealDbLiveQueryOpenResponse)
        {
            // Do something...
        }
        if (response is SurrealDbLiveQueryCreateResponse<Person> create)
        {
            // Use the `Result` record
        }
        if (response is SurrealDbLiveQueryUpdateResponse<Person> update)
        {
            // Use the `Result` record
        }
        if (response is SurrealDbLiveQueryDeleteResponse<Person> delete)
        {
            // Use the `Result` record
        }
        if (response is SurrealDbLiveQueryCloseResponse)
        {
            // Do something...
        }
    });

You can also use the OfType operator to filter the responses.

liveQuery
    .ToObservable()
    .OfType<SurrealDbLiveQueryCreateResponse<Person>>()
    .Select(response => response.Result)
    .Subscribe((record) => 
    {
        // Use the created record
    });

Note that this pattern is already simplified via methods available on the SurrealDbLiveQuery object. You can learn more about these methods in the LiveQuery methods section.

.LiveQuery<T>()

Initiate a live query from a SurrealQL statement.

Method Syntax
await db.LiveQuery<T>(sql)

Arguments

Example usage

const string table = "person"; 
await using var liveQuery = await db.LiveQuery<Person>($"LIVE SELECT * FROM type::table({table});");

// Consume the live query...

SurrealDbLiveQuery methods

The SurrealDbLiveQuery object provides the following methods:

GetResults()

Returns an enumerator that iterates asynchronously through the collection of results (all actions CREATE, UPDATE and DELETE, except OPEN and CLOSE).

Arguments

Example usage

await using var liveQuery = await db.LiveRawQuery<Person>("LIVE SELECT * FROM person;");

await foreach (var response in liveQuery.GetResults())
{
    // Either a Create, Update or Delete notification...

    if (response is SurrealDbLiveQueryCreateResponse<Person> create)
    {
        // Use the `Result` record
    }
    if (response is SurrealDbLiveQueryUpdateResponse<Person> update)
    {
        // Use the `Result` record
    }
    if (response is SurrealDbLiveQueryDeleteResponse<Person> delete)
    {
        // Use the `Result` record
    }
}

GetCreatedRecords()

Returns an enumerator that iterates asynchronously through the collection of created records.

Arguments

Example usage

await using var liveQuery = await db.LiveRawQuery<Person>("LIVE SELECT * FROM person;");

await foreach (var record in liveQuery.GetCreatedRecords())
{
    // Use the created record
}

GetUpdatedRecords()

Returns an enumerator that iterates asynchronously through the collection of updated records.

Arguments

Example usage

await using var liveQuery = await db.LiveRawQuery<Person>("LIVE SELECT * FROM person;");

await foreach (var record in liveQuery.GetUpdatedRecords())
{
    // Use the updated record
}

GetDeletedRecords()

Returns an enumerator that iterates asynchronously through the collection of deleted records.

Arguments

Example usage

await using var liveQuery = await db.LiveRawQuery<Person>("LIVE SELECT * FROM person;");

await foreach (var record in liveQuery.GetDeletedRecords())
{
    // Use the deleted record
}

KillAsync()

Kills the underlying live query.

Method Syntax
await liveQuery.KillAsync(cancellationToken)

Arguments

Example usage

var liveQuery = await db.LiveRawQuery<Person>("LIVE SELECT * FROM person;");

// Consume the live query...

// Manually kill the live query
await liveQuery.KillAsync();

.LiveRawQuery<T>()

Initiate a live query from a SurrealQL statement, based on a raw SurrealQL query.

Method Syntax
await db.LiveRawQuery<T>(sql, params)

Arguments

Example usage

await using var liveQuery = await db.LiveRawQuery<Person>("LIVE SELECT * FROM person;");

// Consume the live query...

.LiveTable<T>()

Initiate a live query from a table.

Method Syntax
await db.LiveTable<T>(table, diff)

Arguments

Example usage

await using var liveQuery = await db.LiveTable<Person>("person");

// Consume the live query...

.Kill()

Kills a running live query by it’s UUID.

Method Syntax
await db.Kill(queryUuid)

Arguments

Example usage

await db.Kill(queryUuid);

Live Actions

A live query event can be one of the following: