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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.
The following namespaces are no longer valid and have to be removed:
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?
DocumentConventions.ThrowIfQueryPageSizeIsNotSetcan 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).
- Set on all queries maximum number of results that you expect using
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();
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 for
session.Query was and still is
AND, but the operator for
DocumentQuery have changed from
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:
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 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:
RavenQueryStatistics has been renamed to
As has been removed in favor to built-in LINQ method
ProjectFromIndexFieldsInto has been renamed to