WITH (NOLOCK) và WITH (READPAST) là các table hint trong SQL Server giúp quản lý tính đồng thời theo những cách khác nhau — NOLOCK đọc dữ liệu chưa cam kết (dirty), trong khi READPAST bỏ qua các hàng bị khóa, tránh đọc dữ liệu bẩn nhưng ...
By Huy VũWITH (NOLOCK) và WITH (READPAST) là các table hint trong SQL Server giúp quản lý tính đồng thời theo những cách khác nhau — NOLOCK đọc dữ liệu chưa cam kết (dirty), trong khi READPAST bỏ qua các hàng bị khóa, tránh đọc dữ liệu bẩn nhưng ...
By Huy VũTôi đã đề cập đến việc NOLOCK mang lại kết quả ngẫu nhiên như thế nào khi bạn truy vấn dữ liệu đang thay đổi, và đó là một minh chứng rất mạnh mẽ để cho những người nghĩ rằng NOLOCK an toàn khi sử dụng trong môi trường production thấy. T...
By Huy VũCách thay đổi mức độ cô lập (isolation levels) mà không bị mất kiểm soát. Một khách hàng đã nói với tôi một điều rất thú vị vào ngày hôm nọ. Anh ấy nói: “Chúng ta đã thảo luận trước đây về lý do tại sao chúng ta muốn bắt đầu sử dụng opti...
By Huy Vũ
Here's a scenario: A user makes a request to your API, it starts processing, then the user gets impatient and closes their browser. Your API? Still chugging away, doing work that nobody will ever see. Database queries running, external A...
By Huy Vũ
Hallelujah. With current versions of Entity Framework, when developers add a mix of parameters and specific values to their query like this: C# 12345 async Task<List<Post>> GetPosts(int id) => await context.Posts .Where( e => e.Title == ...
By Huy Vũ
Exception handling can make or break your application. If exceptions aren’t handled properly, your API could leak sensitive stack traces, return inconsistent error formats, or worse - crash entirely. I’ve seen production systems go down ...
By Huy Vũ
SQL Server’s Query Store is the closest thing the engine has to a flight data recorder. Before Query Store existed, when a query suddenly became slow there was often no evidence to work with. The execution plan that caused the problem wa...
By Huy VũHallelujah. With current versions of Entity Framework, when developers add a mix of parameters and specific values to their query like this: C# 12345 async Task<List<Post>> GetPosts(int id) => await context.Posts .Where( e => e.Title == ...
By Huy Vũ
Recently I covered some of the T-SQL improvements in SQL Server 2022 here, and Aaron Bertrand covered additional improvements here. Those improvements were introduced in CTP 2.0. Microsoft just announced the release of SQL Server 2022 CT...
By selectgo
SQL Server’s automatic statistics update feature is designed to keep the query optimizer’s cardinality estimates accurate as data changes. When it works, it is invisible. When it silently fails, the optimizer continues making execution p...
By Huy VũException handling can make or break your application. If exceptions aren’t handled properly, your API could leak sensitive stack traces, return inconsistent error formats, or worse - crash entirely. I’ve seen production systems go down ...
By Huy Vũ
Slapping WITH (NOLOCK) on your query seems to make it go faster – but what’s the drawback? Let’s take a look. We’ll start with the free StackOverflow.com public database – any one of them will do, even the 10GB mini one – and run this qu...
By Huy VũI’ve already covered how NOLOCK gives you random results when you’re querying data that’s changing, and that’s a really powerful demo to show folks who think NOLOCK is safe to use in production. However, I’ve gotten a question from sever...
By Huy Vũ
How to change isolation levels without losing your marbles. A client said the coolest thing to me the other day. He said, “We talked before about why we would want to start using optimistic locking in our code. How do we get there?” If y...
By Huy Vũ
When you run a SELECT COUNT(*), the speed of the results depends a lot on the structure & settings of the database. Let’s do an exploration of the Votes table in the Stack Overflow database, specifically the 2018-06 ~300GB version where ...
By Huy Vũ
Great volumes have been written about table partitioning. It’s a complex feature and you can read for days to just understand how you might apply it. But will it improve performance for you? Table partitioning produces great benefits for...
By Huy Vũ