Query vs DocumentQuery

Query:

• The Query API supports LINQ, the essential data access solution in .NET.

• The API exposed by the Query method is a wrapper of DocumentQuery and is built on top of it.

• When using Query, the query is translated into a DocumentQuery object,
  which then builds into an RQL that is sent to the server.

• The available Query methods and extensions are listed here.

DocumentQuery:

• DocumentQuery does Not support LINQ.

• It exposes a lower-level API that provides more flexibility and control when building a query.

• When using DocumentQuery, the query is translated into an RQL that is sent to the server.

• The available DocumentQuery methods and extensions are listed here.

• Query is immutable while DocumentQuery is mutable.
  You might get different results if you try to reuse a query.

• The usage of the Query method in the following example:

  IRavenQueryable<User> query = session
      .Query<User>()
      .Where(x => x.Name.StartsWith("A"));
  
  IRavenQueryable<User> ageQuery = query
      .Where(x => x.Age > 21);
  
  IRavenQueryable<User> eyeQuery = query
      .Where(x => x.EyeColor == "blue");

  will result with the following Lucene-syntax queries:

  query: from Users where startsWith(Name, 'A')

  ageQuery: from Users where startsWith(Name, 'A') and Age > 21

  eyeQuery: from Users where startsWith(Name, 'A') and EyeColor = 'blue'

• A similar usage with DocumentQuery:

  IDocumentQuery<User> documentQuery = session
      .Advanced
      .DocumentQuery<User>()
      .WhereStartsWith(x => x.Name, "A");
  
  IDocumentQuery<User> ageDocumentQuery = documentQuery
      .WhereGreaterThan(x => x.Age, 21);
  
  IDocumentQuery<User> eyeDocumentQuery = documentQuery
      .WhereEquals(x => x.EyeColor, "blue");
  
  // Here all of the DocumentQuery variables have the same reference

  will result with the following Lucene queries:

  documentQuery: from Users where startsWith(Name, 'A')
  (before creating ageDocumentQuery)

  ageDocumentQuery: from Users where startsWith(Name, 'A') and Age > 21
  (before creating eyeDocumentQuery)

  eyeDocumentuery: from Users where startsWith(Name, 'A') and Age > 21 and EyeColor = 'blue'

  All created Lucene queries are the same query (actually the same instance).
  This is an important hint to be aware of if you are going to reuse DocumentQuery.

• Starting from version 4.0, both Query and DocumentQuery use AND as the default operator.
  (Previously, Query used AND and DocumentQuery used OR).

• This behavior can be modified by calling UsingDefaultOperator:

session
    .Advanced
    .DocumentQuery<User>()
    .UsingDefaultOperator(QueryOperator.Or);