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1. Database table structure optimization a. select the most applicable field attribute and index According to the actual situation: for example, limit the length of varchar field, set fixed length char; use enum. b. use connections instead of subqueries According to the actual situation: try not to use subquery if it can be rewritten as join.// ...

This is the function of the attribute table of the grid data of or. In my attribute table, there are count and value fields, where value is the elevation value of the grid data, count is the number of times value appears in the image, and the function of this program is to get the maximum count, so as t ...

1. Query before modifying The entity is obtained by context, so the context immediately begins to trace it. When you change the tracking entity's property value, the context changes the entity's EntityState to Modified, and ChangeTracker records the old and new property values. When SaveChanges is c ...

Analysis: Because the optimizer cannot judge or obtain the statistics of the remote table, the original execution plan will execute by default by pulling the remote table (regardless of its size) to the local and reconnecting, so if the remote table is large, it will be relatively slow, and the above qu ...

The following Automatic Workload Repository is represented by AWR 12c is self managed most of the time. Maintenance tasks run automatically and diagnostic information is collected regularly. Diagnosing performance problems is time-consuming and requires skills. 12c has the Alert system and diagnostic ad ...

This article describes how to deploy a sharded database with adg function. 1. Environment introduction The roles and database versions of each node are shown in the following table:The instance name is named by the system itself. 2. Create Shard Catalog Database Here we use the silent method to create the directory database on odb01. [oracle@o ...

http://book.pythontips.com/en/latest/args_and_kwargs.html https://stackoverflow.com/questions/3394835/use-of-args-and-kwargs Many new Python users will be confused about the source code of github and python standard library as well as various * args and **kwargs in the online examples. Here's an explanation. First of all: *Args and * * kwar ...

order This paper mainly studies the deleteConfig of nacos config ConfigController nacos-1.1.3/config/src/main/java/com/alibaba/nacos/config/server/controller/ConfigController.java @Controller @RequestMapping(Constants.CONFIG_CONTROLLER_PATH) public class ConfigController { private static final Logger log = LoggerFactory.getLogger(ConfigCon ...

Summary                         But without special business requirements, the official logstash has its advantages.    when using logstash, we should first understand its characteristics, and then decide whether to use i ...

mysql introduction and installation mysql introduction mysql is a famous open source relational database. It was first opened by AB company, and later it came to Sun company. After Sun was acquired by Oracle, mysql was owned by Oracle. Since then, mysql has been commercialized, and the database named mariadb has been open-source as a branch of ...