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Sort Query Results

Order by field value​

  • Use OrderBy or OrderByDescending to order the results by the specified document-field.
List<Product> products = session
   // Make a dynamic query on the Products collection    
  .Query<Product>()
   // Apply filtering (optional)
  .Where(x => x.UnitsInStock > 10)
   // Call 'OrderBy', pass the document-field by which to order the results
  .OrderBy(x => x.UnitsInStock)
  .ToList();

// Results will be sorted by the 'UnitsInStock' value in ascending order,
// with smaller values listed first.

Ordering Type:

  • By default, the OrderBy methods will determine the OrderingType from the property path expression
    and specify that ordering type in the generated RQL that is sent to the server.

  • E.g. in the above example, ordering by x => x.UnitsInStock will result in OrderingType.Long
    because that property data type is an integer.

  • Different ordering can be forced - see Force ordering type below.

Order by score​

  • When querying with some filtering conditions, a basic score is calculated for each item in the results
    by the underlying indexing engine.

  • The higher the score value the better the match.

  • Use OrderByScore or OrderByScoreDescending to order by this score.

List<Product> products = session
  .Query<Product>()
   // Apply filtering
  .Where(x => x.UnitsInStock < 5 || x.Discontinued)
   // Call 'OrderByScore'
  .OrderByScore()
  .ToList();

// Results will be sorted by the score value
// with best matching documents (higher score values) listed first.

Get resulting score:​

The score details can be retrieved by either:

  • Request to include explanations:
    You can get the score details and see how it was calculated by requesting to include explanations in the query. Currently, this is only available when using Lucene as the underlying indexing engine.
    Learn more in Include query explanations.

  • Get score from metadata:

    • The score is available in the @index-score metadata property within each result.
      Note the following difference between the underlying indexing engines:

      • When using Lucene:
        This metadata property is always available in the results.
        Read more about Lucene scoring here.

      • When using Corax:
        In order to enhance performance, this metadata property is Not included in the results by default.
        To get this metadata property you must set the Indexing.Corax.IncludeDocumentScore configuration value to true.
        Learn about the available methods for setting an indexing configuration key in this indexing-configuration article.

    • The following example shows how to get the score from the metadata of the resulting entities that were loaded to the session:

// Make a query:
// =============

List<Employee> employees = session
  .Query<Employee>()
  .Search(x => x.Notes, "English")
  .Search(x => x.Notes, "Italian", boost: 10)
  .ToList();

// Get the score:
// ==============

// Call 'GetMetadataFor', pass an entity from the resulting employees list
var metadata = session.Advanced.GetMetadataFor(employees[0]);

// Score is available in the '@index-score' metadata property
var score = metadata[Constants.Documents.Metadata.IndexScore];

Order by random​

  • Use RandomOrdering to randomize the order of the query results.

  • An optional seed parameter can be passed.

List<Product> products = session
  .Query<Product>()
  .Where(x => x.UnitsInStock > 10)
   // Call 'Customize' with 'RandomOrdering'
  .Customize(x => x.RandomOrdering())
   // An optional seed can be passed, e.g.:
   // .Customize(x => x.RandomOrdering('someSeed'))
  .ToList();

// Results will be randomly ordered.

Order by spatial​

  • If your data contains geographical locations,
    spatial query results can be sorted based on their distance from a specific point.

  • See detailed explanation in Spatial Sorting.

Order by count (aggregation query)​

  • The results of a group-by query can be sorted by the Count aggregation operation used in the query.
var numberOfProductsPerCategory = session
  .Query<Product>()
   // Make an aggregation query
  .GroupBy(x => x.Category)
  .Select(x => new
  {
      // Group by Category
      Category = x.Key,
      // Count the number of product documents per category
      Count = x.Count()
  })
   // Order by the Count value
  .OrderBy(x => x.Count)
  .ToList();

// Results will contain the number of Product documents per category
// ordered by that count in ascending order.

Order by sum (aggregation query)​

  • The results of a group-by query can be sorted by the Sum aggregation operation used in the query.
var numberOfUnitsInStockPerCategory = session
  .Query<Product>()
   // Make an aggregation query
  .GroupBy(x => x.Category)
  .Select(x => new
  {
      // Group by Category
      Category = x.Key,
      // Sum the number of units in stock per category
      Sum = x.Sum(x => x.UnitsInStock)
  })
   // Order by the Sum value
  .OrderBy(x => x.Sum)
  .ToList();

// Results will contain the total number of units in stock per category
// ordered by that number in ascending order.

Force ordering type​

  • By default, the OrderBy methods will determine the OrderingType from the property path expression
    and specify that ordering type in the generated RQL that is sent to the server.

  • A different ordering can be forced by passing the ordering type explicitly to OrderBy or OrderByDescending.

  • The following ordering types are available:

    • OrderingType.Long
    • OrderingType.Double
    • OrderingType.AlphaNumeric
    • OrderingType.String (lexicographic ordering)

  • When using RQL directly, if no ordering type is specified, then the server defaults to lexicographic ordering.

Using alphanumeric ordering example:

  • When ordering mixed-character strings by the default lexicographical ordering
    then comparison is done character by character based on the Unicode values.
    For example, "Abc9" will come after "Abc10" since 9 is greater than 1.

  • If you want the digit characters to be ordered as numbers then use alphanumeric ordering
    where "Abc10" will result after "Abc9".

List<Product> products = session
  .Query<Product>()
   // Call 'OrderBy', order by field 'QuantityPerUnit'
   // Pass a second param, requesting to order the text alphanumerically
  .OrderBy(x => x.QuantityPerUnit, OrderingType.AlphaNumeric)
  .ToList();
// Running the above query on the NorthWind sample data,
// would produce the following order for the QuantityPerUnit field:
// ================================================================

// "1 kg pkg."
// "1k pkg."
// "2 kg box."
// "4 - 450 g glasses"
// "5 kg pkg."
// ...

// While running with the default Lexicographical ordering would have produced:
// ============================================================================

// "1 kg pkg."
// "10 - 200 g glasses"
// "10 - 4 oz boxes"
// "10 - 500 g pkgs."
// "10 - 500 g pkgs."
// ...

Chain ordering​

  • It is possible to chain multiple orderings in the query.
    Any combination of secondary sorting is possible as the fields are indexed independently of one another.

  • There is no limit on the number of sorting actions that can be chained.

  • This is achieved by using the ThenBy (ThenByDescending) and ThenByScore (ThenByScoreDescending) methods.

List<Product> products = session
  .Query<Product>()
  .Where(x => x.UnitsInStock > 10)
   // Apply the primary sort by 'UnitsInStock'
  .OrderByDescending(x => x.UnitsInStock)
   // Apply a secondary sort by the score (for products with the same # of units in stock)
  .ThenByScore()
   // Apply another sort by 'Name' (for products with same # of units in stock and same score)
  .ThenBy(x => x.Name)
  .ToList();

// Results will be sorted by the 'UnitsInStock' value (descending),
// then by score,
// and then by 'Name' (ascending).

Custom sorters​

  • The Lucene indexing engine allows you to create your own custom sorters.
    Custom sorters are not supported by Corax.

  • Custom sorters can be deployed to the server by either:

  • Once the custom sorter is deployed, you can sort the query results with it.

List<Product> products = session
  .Query<Product>()
  .Where(x => x.UnitsInStock > 10)
   // Order by field 'UnitsInStock', pass the name of your custom sorter class
  .OrderBy(x => x.UnitsInStock, "MySorter")
  .ToList();

// Results will be sorted by the 'UnitsInStock' value
// according to the logic from 'MySorter' class

Syntax​

// OrderBy overloads:
IOrderedQueryable<T> OrderBy<T>(string path, OrderingType ordering);
IOrderedQueryable<T> OrderBy<T>(Expression<Func<T, object>> path, OrderingType ordering);
IOrderedQueryable<T> OrderBy<T>(string path, string sorterName);
IOrderedQueryable<T> OrderBy<T>(Expression<Func<T, object>> path, string sorterName);

// OrderByDescending overloads:
IOrderedQueryable<T> OrderByDescending<T>(string path, OrderingType ordering);
IOrderedQueryable<T> OrderByDescending<T>(Expression<Func<T, object>> path, OrderingType ordering);
IOrderedQueryable<T> OrderByDescending<T>(string path, string sorterName);
IOrderedQueryable<T> OrderByDescending<T>(Expression<Func<T, object>> path, string sorterName);
ParameterTypeDescription
pathstringThe name of the field to sort by
pathExpression<Func<T, object>>A lambda expression to the field by which to sort
orderingQueryStatisticsThe ordering type that will be used to sort the results:
OrderingType.Long
OrderingType.Double
OrderingType.AlphaNumeric
OrderingType.String (default)
sorterNamestringThe name of your custom sorter class