Session: Querying: How to stream query results?

Query results can be streamed using Stream method from Advanced session operations.

Syntax

// Define a query on a collection
IRavenQueryable<Employee> query = session
  .Query<Employee>()
  .Where(x => x.FirstName == "Robert");

// Call 'Stream' to execute the query
// Optionally, pass an 'out param' for getting the query stats
IEnumerator<StreamResult<Employee>> streamResults = 
  session.Advanced.Stream(query, out StreamQueryStatistics streamQueryStats);

// Read from the stream
while (streamResults.MoveNext())
{
  // Process the received result
  StreamResult<Employee> currentResult = streamResults.Current;
  
  // Get the document from the result
  // This entity will Not be tracked by the session
  Employee employee = currentResult.Document;
  
  // The currentResult item also provides the following:
  var employeeId  = currentResult.Id;
  var documentMetadata = currentResult.Metadata;
  var documentChangeVector = currentResult.ChangeVector;

  // Can get info from the stats, i.e. get number of total results
  int totalResults = streamQueryStats.TotalResults;
  // Get the Auto-Index that was used/created with this dynamic query
  string indexUsed = streamQueryStats.IndexName;
}

Parameters
query	IQueryable or IDocumentQuery	Query to stream results for.
queryHeaderInformation	QueryHeaderInformation	Information about performed query.

Return Value
IEnumerator<StreamResult>	Enumerator with entities.
QueryHeaderInformation	Information about performed query.

Example I

// Define a document query on a collection
IDocumentQuery<Employee> query = session
  .Advanced
  .DocumentQuery<Employee>()
  .WhereEquals(x => x.FirstName, "Robert");

// Call 'Stream' to execute the query
// Optionally, add an out param for getting the query stats
IEnumerator<StreamResult<Employee>> streamResults = 
  session.Advanced.Stream(query, out StreamQueryStatistics streamQueryStats);

// Read from the stream
while (streamResults.MoveNext())
{
  // Process the received result
  StreamResult<Employee> currentResult = streamResults.Current;
  
  // Get the document from the result
  // This entity will Not be tracked by the session
  Employee employee = currentResult.Document;
      
  // The currentResult item also provides the following:
  var employeeId  = currentResult.Id;
  var documentMetadata = currentResult.Metadata;
  var documentChangeVector = currentResult.ChangeVector;
  
  // Can get info from the stats, i.e. get number of total results
  int totalResults = streamQueryStats.TotalResults;
  // Get the Auto-Index that was used/created with this dynamic query
  string indexUsed = streamQueryStats.IndexName;
}

Example II

// Define a raw query using RQL
IRawDocumentQuery<Employee> query = session
  .Advanced
  .RawQuery<Employee>("from Employees where FirstName = 'Robert'");

// Call 'Stream' to execute the query
IEnumerator<StreamResult<Employee>> streamResults = session.Advanced.Stream(query);

while (streamResults.MoveNext())
{
  StreamResult<Employee> currentResult = streamResults.Current;
  Employee employee = streamResults.Current.Document;
}

Remarks

Streaming results only works for queries that were made against a (predefined) static index.