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Querying : Query vs DocumentQuery

Why does the RavenDB client offer two ways of querying by exposing the Query as well as DocumentQuery methods? What are the differences between them?

DocumentQuery is the lower level API that we use to query RavenDB, but it does not support LINQ, the mandatory data access solution in .NET. We created Query to be the LINQ endpoint for RavenDB.

The entire LINQ API is a wrapper of DocumentQuery and is built on top on that. When you use Query, it always is translated into the DocumentQuery object, which then builds a RQL-syntax query that is sent to the server. However, we still expose DocumentQuery in advanced options to allow the users to have the full power of RQL available to them.

Immutability

DocumentQuery is mutable while Query is immutable. 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 that the queries will be translated into 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'

The similar usage of 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 are the same references

documentQuery - from Users where startsWith(Name, 'A') (before creating ageQuery)

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

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

In results, all created Lucene queries are the same query (actually the same instance). This is an important hint that you should be aware if you are going to reuse DocumentQuery.

Default Query Operator

Starting from version 4.0, the Query and DocumentQuery have an identical default operator AND (previously Query used AND and DocumentQuery used OR). You are able to change this behavior by using UsingDefaultOperator:

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