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This article mainly explains "how to optimize the database by Java". Interested friends may wish to have a look. The method introduced in this paper is simple, fast and practical. Next let the editor to take you to learn "Java how to optimize the database" bar!

1 to establish an efficient and appropriate index

Anyone can build an index, but it is extremely difficult to build it. Because the index should have both data characteristics and business characteristics, the change of the amount of data will affect the choice of the index, the business characteristics are different, and the optimization ideas of the index are also different. Usually, a field is not used, but hitting a field with "missing index" in a certain scenario will cause the query to slow down instantly. Therefore, it is necessary to define the business scenario in advance and establish an appropriate index.

2 troubleshooting connection resources to show that the situation is closed, pay special attention to the use of database connections in ThreadLocal or streaming computing.

(3) merge short requests according to the principle of CPU spatial locality, for similar data, CPU will be extracted into memory together. In addition, merge requests can also effectively reduce the number of connections. 4 reasonable split of multiple tables join SQL if more than three tables, join is prohibited, if the table knot construction is unreasonable, the application logic is not handled properly, there is a problem with the abstraction of the business model, and the data volume of the name three-standard join will show a geometric multiple increase due to the Cartesian product operation, so this approach is not recommended. In addition, for fields that require join, the data types should be absolutely consistent. When you associate a query with multiple tables, you should make sure that the associated fields are indexed.

(5) using temporary tables is a better choice in some cases. Once encountered a scenario that is not suitable for temporary tables need to be executed for more than 1 hour, the use of temporary tables is reduced to less than 2 minutes. Because in the continuous nested query, it is impossible to make good use of the existing index to improve the query efficiency, so save the intermediate results to the temporary table, then rebuild the index, and then carry on the subsequent data operation through the temporary table. (6) Application layer optimization includes data structure optimization, concurrent multithreading transformation and so on.

7 switch to other databases because different databases aim at different business scenarios, such as Cassandra and MongoDB.

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