NET Provider for SQL Server supports connection pooling.Ģ Cost increases with increased query complexity.ģ Total cost increases proportional to the number of objects returned by the query.Ĥ This overhead is not required for Entit圜lient queries because Entit圜lient queries return an EntityDataReader instead of objects. For more information, see Identity Resolution, State Management, and Change Tracking.ġ When a data source provider implements connection pooling, the cost of opening a connection is distributed across the pool. If the object already exists in the ObjectContext and the query uses the AppendOnly or PreserveChanges merge options, this stage does not affect performance. The process of reading the returned DbDataReader object and creating objects and setting property values that are based on the values in each instance of the DbDataRecord class. For more information, see Identity Resolution, State Management, and Change Tracking. If the PreserveChanges, or OverwriteChanges option is used, the object is updated before it is returned. If an existing ObjectStateEntry can be found for the EntityKey, the existing object is returned. An EntityKey is generated for each tracked object that the query returns and is used to create an ObjectStateEntry in the ObjectStateManager. If the query uses the AppendOnly, PreserveChanges, or OverwriteChanges merge option, query results are tracked in the ObjectStateManager. If a query uses the NoTracking merge option, this stage does not affect performance. Once for each object that a query returns. Types are loaded and validated against the types that the conceptual model defines. Because most data sources cache query plans, later executions of the same query may take even less time. The cost of executing the command against the data source by using the ADO.NET data provider. Also parameterizing in-memory collections in compiled LINQ queries is not allowed. Note: LINQ to Entities queries that apply the Enumerable.Contains operator to in-memory collections are not automatically cached. For general information about LINQ query execution, see LINQ to Entities. For more information, see Compiled Queries (LINQ to Entities). You can still use compiled LINQ queries to reduce this cost in later executions and compiled queries can be more efficient than LINQ queries that are automatically cached. Because now both Entity SQL query commands and LINQ queries are cached, later executions of the same query take less time. Includes the costs to compose the query command, generate a command tree based on model and mapping metadata, and define the shape of the returned data. For more information, see How to: Pre-Generate Views to Improve Query Performance. Because of the high cost of generating these views, you can pre-generate the views and add them to the project at design-time. (Can be pre-generated.)īefore the Entity Framework can execute a query against a conceptual model or save changes to the data source, it must generate a set of local query views to access the database. For more information, see Managing Connections and Transactions. You can also explicitly open the connection. This metadata is cached globally and is available to other instances of ObjectContext in the same application domain.īecause an open connection to the database consumes a valuable resource, the Entity Framework opens and closes the database connection only as needed. Model and mapping metadata used by the Entity Framework is loaded into a MetadataWorkspace. The following table describes this series of operations. In order to better understand the performance of queries in the Entity Framework, it is helpful to understand the operations that occur when a query executes against a conceptual model and returns data as objects. This topic describes performance characteristics of the ADO.NET Entity Framework and provides some considerations to help improve the performance of Entity Framework applications.
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