GPT teaches you how to answer Baidu interviews - detailed tutorial

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Hello everyone, my name is Mavericks, and GPT has been really eye-opening recently. I recently plan to write a series of articles using GPT to answer interviewer back-end interview questions. Hope these articles are helpful to everyone! Let’s start introducing interview questions and corresponding answers now!

Brief description of Semaphore

Semaphore is a mechanism used to control concurrent access, which can limit the number of threads accessing a resource at the same time. In a multi-threaded environment, when a shared resource needs to limit concurrent access, Semaphore can be used to achieve

In my project, we use semaphores (Semaphore) to control concurrent access to the database. In high-concurrency scenarios, multiple threads may request operations on the database at the same time, and concurrent access to the database is limited. In order to avoid competition and conflicts in database access, we use semaphores to limit the number of threads that access the database at the same time

In the project, we use the Semaphore construction method to set a license number, which represents the maximum number of threads that can concurrently access the database. quantity. When a thread needs to access the database, it first needs to obtain a license through the acquire method. At this time, the Semaphore counter will be decremented by one. If the value of the counter is 0 at this time, that is, all licenses are occupied, the thread will enter the sleep state and wait for other threads to return the license. When a thread completes access to the database, it needs to return the license through the release method. At this time, the Semaphore counter will be increased by one, and other threads waiting for the license will have the opportunity to obtain the license and continue to access the database.

By using Semaphore, we can effectively control the number of concurrent accesses to the database, avoid fierce competition and conflicts, and improve the concurrent processing capabilities and performance of the system.

In addition to using mechanisms such as locks and thread pools, we also combine other concurrency control technologies in our project to further optimize the performance and efficiency of concurrent access to the database. By rationally using these technologies, we successfully solved the problem of database access in high concurrency scenarios and ensured the consistency and reliability of data.

I hope my understanding of Semaphore and its application in the project can be answered. You helped. So, why introduce indexes?

The index is introduced to improve the efficiency of data query. An index is a data structure that speeds up database queries by creating an index on a certain column. As the amount of data in the table becomes larger and larger, the impact of indexes on performance becomes more important.

In my previous project, we used indexes to optimize database queries. This project is an e-commerce platform with a large amount of product data that needs to be queried. We created indexes on key columns of the product table, such as product name, product category, etc. By creating an index, we can quickly locate product data that meets the query conditions, greatly improving query efficiency and response speed.

Specifically, indexes can help the database quickly locate data that meets query conditions without traversing the entire data table. When we make a query, the database engine will first check if an applicable index exists, and if so, it will use the index to locate the data instead of a full table scan. This can greatly reduce the number of IO operations and improve query efficiency.

In our project, we noticed that it is very important to choose the appropriate index. Incorrect index selection can result in degraded query performance. We analyzed common query operations and fields and selected suitable columns for indexing. At the same time, in order to reduce the impact of indexes on write operations, we have performed reasonable index optimization on frequently updated columns, such as using partial indexes or covering indexes

In general, the introduction of indexes can greatly improve the database Query efficiency, especially when the amount of data is large. Reasonable selection of indexes and index optimization can further improve query performance.

In my project, we optimized the product query operation of the e-commerce platform and improved the user experience through reasonable use of indexes. At the same time, we also realize that index maintenance and optimization are ongoing tasks that need to be adjusted and optimized according to actual conditions to ensure high performance and stability of the system.

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