Session: Querying: How to perform queries lazily?

In some situations query execution must be delayed. To cover such scenario Lazily and many others query extensions has been introduced.

Lazily and LazilyAsync

// Define a lazy query
Lazy<IEnumerable<Employee>> lazyEmployees = session
  .Query<Employee>()
  .Where(x => x.FirstName == "Robert")
   // Add a call to 'Lazily'
  .Lazily();

IEnumerable<Employee> employees = lazyEmployees.Value; // Query is executed here

Parameters
onEval	Action<IEnumerable<TResult>>	Action that will be performed on query results.

Return Value
Lazy<IEnumerable<TResult>>	Lazy query initializer returning query results.

Example

// Define a lazy query
Lazy<Task<IEnumerable<Employee>>> lazyEmployees = asyncSession
  .Query<Employee>()
  .Where(x => x.FirstName == "Robert")
   // Add a call to 'LazilyAsync'
  .LazilyAsync();

IEnumerable<Employee> employees = await lazyEmployees.Value; // Query is executed here

or

// Define a lazy DocumentQuery
Lazy<IEnumerable<Employee>> lazyEmployees = session.Advanced
  .DocumentQuery<Employee>()
  .WhereEquals(x => x.FirstName, "Robert")
   // Add a call to 'Lazily'
  .Lazily();

IEnumerable<Employee> employees = lazyEmployees.Value; // DocumentQuery is executed here

CountLazily

// Define a lazy count query
Lazy<int> lazyCount = session
  .Query<Employee>()
  .Where(x => x.FirstName == "Robert")
   // Add a call to 'CountLazily'
  .CountLazily();

int count = lazyCount.Value; // Query is executed here

Return Value
Lazy<IEnumerable<TResult>>	Lazy query initializer returning count of matched documents.

Example

// Define a lazy count query
Lazy<Task<int>> lazyCount = asyncSession
  .Query<Employee>()
  .Where(x => x.FirstName == "Robert")
   // Add a call to 'CountLazilyAsync'
  .CountLazilyAsync();

int count = await lazyCount.Value; // Query is executed here

SuggestLazy

// Define a lazy DocumentQuery
Lazy<int> lazyCount = session.Advanced
  .DocumentQuery<Employee>()
  .WhereEquals(x => x.FirstName, "Robert")
   // Add a call to 'CountLazily'
  .CountLazily();

int count = lazyCount.Value; // DocumentQuery is executed here

Parameters
query	SuggestionQuery	A suggestion query definition containing all information required to query a specified index.

Return Value
Lazy<SuggestionQueryResult>	Lazy query initializer containing array of all suggestions for executed query.

Example

// Define a lazy suggestion query
Lazy<Dictionary<string, SuggestionResult>> lazySuggestions = session
  .Query<Product>()
  .SuggestUsing(builder => builder.ByField(x => x.Name, "chaig"))
   // Add a call to 'ExecuteLazy'
  .ExecuteLazy();

Dictionary<string, SuggestionResult> suggest = lazySuggestions.Value; // Query is executed here
List<string> suggestions = suggest["Name"].Suggestions;

ToFacetsLazy

// Define a lazy suggestion query
Lazy<Task<Dictionary<string, SuggestionResult>>> lazySuggestions = asyncSession
  .Query<Employee>()
  .SuggestUsing(builder => builder.ByField("Name", "chaig"))
   // Add a call to 'ExecuteLazyAsync'
  .ExecuteLazyAsync();

Dictionary<string, SuggestionResult> suggest = await lazySuggestions.Value; // Query is executed here
List<string> suggestions = suggest["Name"].Suggestions;

Parameters
facets	List<Facet>	List of facets required to perform a facet query (mutually exclusive with facetSetupDoc).
facetSetupDoc	string	Document key that contains predefined FacetSetup (mutually exclusive with facets).
start	int	number of results that should be skipped. Default: 0.
pageSize	int	maximum number of results that will be retrieved. Default: null.

Return Value
Lazy<FacetResults>	Lazy query initializer containing Facet query results with query Duration and list of Results - one entry for each term/range as specified in [FacetSetup] document or passed in parameters.

Example

// Define a lazy DocumentQuery
Lazy<Dictionary<string, SuggestionResult>> lazySuggestions = session.Advanced
  .DocumentQuery<Employee>()
  .SuggestUsing(builder => builder.ByField("Name", "chaig"))
   // Add a call to 'ExecuteLazy'
  .ExecuteLazy();

Dictionary<string, SuggestionResult> suggest = lazySuggestions.Value; // DocumentQuery is executed here
List<string> suggestions = suggest["FullName"].Suggestions;