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Migration : How to migrate Queries from 3.x?

Following changes occurred in 4.0 and need to be considered when migration is done.

Namespaces

The following namespaces are no longer valid and have to be removed:

  • Raven.Client.Linq
  • Raven.Json.Linq

Paging

There is no longer a default page size send from the client API (128 by default) and maximum page size that to which server will cut the results (1024 by default).

Following query will return all results from the database (even when there is 1M of them):

List<Employee> employees = session
    .Query<Employee>()
    .ToList();

What can be done to mitigate this?

  1. DocumentConventions.ThrowIfQueryPageSizeIsNotSet can be set to true so all queries will throw if their page size is not explicitly set (even when you have just a few records in the database, check is done on the client-side before request is sent to the server).
  2. Set on all queries maximum number of results that you expect using .Take(pageSize) method.

To fix previous example we will set the convention to true and add Take to the query:

store.Conventions.ThrowIfQueryPageSizeIsNotSet = true;

List<Employee> employees = session
    .Query<Employee>()
    .Take(128)
    .ToList();

Performance Hint

If the number of records exceeds 2048 (default value that can be changed by PerformanceHints.MaxNumberOfResults configuration option) then performance hint notification will be issued and visible in the Studio. Giving you enough information to perform counter-measures if necessary.

You can read more about paging in our dedicated article.

Transformers and Projections

Transformers have been removed from the RavenDB. Please read our migration article tackling this change. The article can be found here.

Default Operator

Default operator for session.Query was and still is AND, but the operator for DocumentQuery have changed from OR to AND. We have created a dedicated article that helps you with migration. It can be found here.

Waiting for Non Stale Results

The following methods have been removed:

  • WaitForNonStaleResultsAsOf
  • WaitForNonStaleResultsAsOfNow

You should use WaitForNonStaleResults instead. Its behavior has changed in 4.0 - it's like WaitForNonStaleResultsAsOfNow in 3.x. Please read a dedicated article discussing how to deal with non stale results.

List<Employee> employees = session
    .Query<Employee>()
    .Customize(x => x.WaitForNonStaleResults())
    .ToList();

Raven/DocumentsByEntityName index

Raven/DocumentsByEntityName is no longer necessary in RavenDB 4.0. You can perform queries directly on collections, in particular we support queries that you can run to modify the docs:

3.x 4.0
var tagName = session
                .Advanced
                .DocumentStore
                .Conventions
                .GetTypeTagName(typeof(User));

session.Advanced.DocumentStore.DatabaseCommands
    .DeleteByIndex(Constants.DocumentsByEntityNameIndex, 
        new IndexQuery()
        {
            Query = $"Tag:{ tagName }"
        });
var operation = store.Operations.Send(
    new DeleteByQueryOperation(new IndexQuery()
    {
        Query = session.Query<User>().ToString() // "from Users"
    }));

RavenQueryStatistics

RavenQueryStatistics has been renamed to QueryStatistics.

As

As has been removed in favor to built-in LINQ method OfType.

ProjectFromIndexFieldsInto

ProjectFromIndexFieldsInto has been renamed to ProjectInto.