Денис Резник "Зачем мне знать SQL и Базы Данных, ведь у меня есть ORM?"
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The document discusses the importance of understanding SQL and database internals even when using ORMs for database interactions. It covers topics such as query performance, parameter sniffing, and the capabilities of various ORMs like Entity Framework and Dapper. The author encourages developers to familiarize themselves with generated SQL and query plans, and to invest time in learning about database operations for better performance.
Денис Резник "Зачем мне знать SQL и Базы Данных, ведь у меня есть ORM?"
- 1. Зачем мне знать SQL и Базы Данных, ведь у меня есть ORM? Денис Резник Intapp, Inc.
- 2. Agenda • .Net ORM History which I remember • Simple Queries • Column List • Lazy Load • Data Types • Data Modification • Complex Query • Parameter Sniffing
- 3. ORM History which I remember • ADO.NET • Data Sets (not too bad) • LLBL Gen, NHibernate (better than data sets) • LINQ to SQL (Awesome!) • Entity Framework should be even more awesome • Entity Framework is more powerful than L2S • Entity Framework Code First • Entity Framework is no so good, so what?
- 4. Simple Query
- 6. Column List
- 8. Lazy Load
- 9. Index Seek … … 1 .. 1M 1 .. 2K 2K+1 .. 4K 1M-2K .. 1M 1 .. 300 301 .. 800 801 .. 1,5K 1,5K+1 .. 2K SELECT * FROM Users WHERE Id = 523
- 10. Index Scan … … 1 .. 1M 1 .. 2K 2K+1 .. 4K 1M-2K .. 1M 1 .. 300 301 .. 800 801 .. 1,5K 1,5K+1 .. 2K SELECT * FROM Users
- 11. Index Range Scan … … 1 .. 1M 1 .. 2K 2K+1 .. 4K 1M-2K .. 1M 1 .. 300 301 .. 800 801 .. 1,5K 1,5K+1 .. 2K SELECT * FROM Users WHERE Id BETWEEN 700 AND 1700
- 12. DEMO: Lazy Load
- 13. Data Types
- 14. DEMO: Data Types
- 17. Complex Query
- 20. Parameter Sniffing - Stored Procedure EXEC ReportCheckSecurityRequest @UserId = 1 Query Processor SQL Server Cache Procedure cache Plan created and cached for the @UserId = 1 Procedure cache EXEC ReportCheckSecurityRequest @UserId = 22 Query executes using the query plan created for @UserId = 1
- 21. Parameter Sniffing – Parametrized Query SELECT * FROM Clients WHERE Id = @Id Query Processor SQL Server Cache Procedure cache Plan created and cached for the @Id = 1 Procedure cache Query executes using the query plan created for @Id = 1 SELECT * FROM Clients WHERE Id = @Id sp_executesql N'SELECT * FROM Clients WHERE Id = @Id', N'@Id int', 1 sp_executesql N'SELECT * FROM Clients WHERE Id = @Id', N'@Id int', 22
- 22. Dynamic SQL – Multiple Plans SELECT * FROM Clients WHERE Id = 1 Query Processor SQL Server Cache Procedure cache New query plan created and cached. Query executed using newly created plan. Procedure cache SELECT * FROM Clients WHERE Id = 22 New query plan again created and cached. Query executed using newly created plan. SELECT * FROM Clients WHERE Id = 1 Query executed using the query plan, created for the first query. Procedure cache
- 24. Summary • ORM is really a nice thing • But it still requires strong SQL background • Database internals knowledge is a skill that very nice to have even in the ORM world • Few Advices • Sometimes check the generated SQL and its query plan • For complex queries consider raw SQL anyway • Consider using Dapper • Invest your time to learn database internals