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For single-process concurrency scenarios, you can use the locks provided by the programming language and corresponding class libraries, such as the Synchronized syntax in Java and the ReentrantLock class, to avoid concurrency problems. If in a distributed scenario, to achieve simultaneous access to code and resources by threads of different clients and to ensure the security of processing shared data under multiple threads, distributed lock technology is required.

An index is a data structure that stores and sorts the values of one or more columns in a database table. It speeds up the search by reducing the number of records that need to be queried in a table. If there is no index, the database will have to perform Full table scan. The index is equivalent to the table of contents in the book, you can quickly find the content you need according to the page number on the table of contents, and improve the query speed.

The full name of CAS is Compare and Swap, which means compare and exchange. It is a lock-free atomic algorithm as well as an optimistic mechanism. CAS is mapped to the operating system as a CPU atomic instruction. The implementation method is based on the assembly instructions of the hardware platform. In Intel’s CPU, the cmpxchg instruction is used, which means that CAS is implemented by hardware, thereby improving efficiency at the hardware level.

Commonly used data structures such as binary search tree (Binary Search Tree, BST) each node can only hold one data, resulting in a high tree height, the data of logically adjacent nodes may be far away, if in memory This is not a big problem for data manipulation in the middle, but because the speed of reading and writing to the disk is much slower than that of the memory, the unit of reading and writing to the disk each time is much larger than the smallest unit of reading and writing the memory.