Shulou(Shulou.com)06/02 Report--

This article mainly explains "the management mode of Redis database". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "the management mode of Redis database".

Database management

Dbsize, select, flushdb/flushall and other commands are mainly provided in Redis. Let's introduce the detailed use of these commands.

1. Switch the database

Select index

We know that there are multiple databases in other relational databases such as Mysql, and basically relational databases determine whether the database is duplicated by name. Unlike in Redis, Redis uses numbers to determine whether the database is duplicated. In Redis, the default database is 0, while the default maximum database is 16.

The select command can choose which database to switch, because the default in Redis starts at 0, so the default maximum is 15. If you exceed this range, Redis will prompt for an error. And between different databases and databases in Redis, the data is out of sync, that is, there is no relationship, as shown in the figure above. Let's use a more vivid diagram to represent the storage between different databases in Redis. As shown in the following figure:

Since there are multiple databases in Redis, can we store the data in production to the specified database and then store the data in the test environment to another database in our daily development? The answer is that technically, of course, yes, but basically not in business, because when we usually use relational databases such as Mysql, we will not store the data in the production environment in the same database instance as the data in the test environment, but basically separate the production environment from the test environment. So it's the same with Redis. In addition, when Redis is distributed in the future, it is only allowed to use database 0, which means that the higher version of Redis has increasingly weakened this feature. Just for the sake of compatibility without removing the function of multi-database. Let's analyze why Redis weakens the functionality of this multi-database.

Redis is single threaded. We have introduced it many times in previous articles. So even if we store different data in different databases according to the business, when executing the relevant commands, they will still have an impact on each other because of single-threading and other reasons.

If we use the function of multi-database in the actual development, then if there are corresponding problems in a database, such as slow query and so on. Then it will affect the performance of other databases, and it is not easy for us to troubleshoot the problem, because compared with a database, it is difficult for us to quickly locate which database the problem is.

Some Redis client tools do not support this ability to select multiple databases. Even if it is supported, it is likely to have an impact on different database data because of negligence.

As we do in actual development, if we want to use the function of multiple databases, we can deploy multiple instances, that is, different ports, to achieve the function of multiple databases, as described in the previous article.

2.flushdb/flushall

Looking at the name, we should be able to guess that both flushdb and flushall are commands to empty the Redis database. The difference between them is that the former clears the data in the current database, while the latter clears the data in all databases. Let's take a look at specific examples.

Let's take a look at flushdb/flushall 's notes:

The flushdb/flushall command will clean up the contents of the current database or all databases in Redis at once. If we make a mistake, it is easy to cause a security accident. In a later article, we will introduce rename-command configuration, while rename-command configuration can avoid the above problems and data recovery when these problems occur.

If there is a large amount of data in the current Redis, the flushdb/flushall command may cause blocking, so use it with caution.

Thank you for your reading, the above is the content of "the management of Redis database", after the study of this article, I believe you have a deeper understanding of the management of Redis database, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.