【MongoDB】4. Usage specification of mongodb

【MongoDB】4. MongoDB The standard of use

Today, I looked through the teacher's book and saw MongoDB Several usage specifications of , I think this is very helpful. Write it down first

1. Database usage specification

Databases are represented by names . You should pay attention to the following points about database naming ：

• The encoding format must be UTF-8 character ;
• An empty string... Is not allowed , namely "";
• Only use ASCII Letters and numbers in the code table , Do not use underscores （_） Special characters other than ;
• Database names are case sensitive ;
• The database name length is limited to 64 Bytes ;
• The database name cannot be the same as the database name reserved by the system , namely admin、local and config database

Suggestions for database naming ：

1. The database name is recommended to be all lowercase
2. It is not recommended to use database names starting with numbers
3. The recommended database naming rule is db_xxxx, That is, the name of "see name, know meaning"

2. Collection usage specification

Collections are identified by name . The following points should be noted about the naming of collections ：

• The encoding format must be UTF-8 character ;
• An empty string... Is not allowed , namely "";
• Set names cannot contain \0 character , That is, empty characters , This character represents the end of the set name ;
• Cannot appear with “System.” The beginning set name , this - Is the reserved prefix for the system collection ;
• Set naming cannot include the following characters “$”;
• The length of the set name is limited to 64 Bytes

Based on the above MongoDB Naming conventions for collections , And put forward five suggestions on collection naming from the perspective of actual development ：

1. It is not recommended to use anything other than _（ Underline ） and .（ spot ） Special characters other than ;
2. It is recommended that all set names be lowercase ;
3. It is not recommended to use set names starting with numbers ;
4. In order to avoid the problems caused by library level lock , Try to write to a larger set using “ Single library single collection ” Structure , For new businesses, try to create new libraries , Instead of creating a new collection in an existing library ;
5. The recommended set naming rule is t_xxxx;
6. Use “.” To separate subsets of different namespace , For example, a blog may contain two subsets , namely blog.posts and blog.authors, and blog It doesn't exist

3. Document usage specification

The type of key in the document is generally string type , Keys can be arbitrary UTF-8 character . Note the following points about the naming of documents ：

• The key in the document cannot contain “\0” character , That is, empty characters ;
• The keys in the document are prohibited from using anything except underscores “” Special characters other than , And it is not recommended to use... At the beginning "";
• It is recommended that all keys in the document be lowercase ;
• Keys in documents are not recommended to start with numbers ;
• It is not recommended to customize “_id” value
• Try to put similar documents in the same set , Scatter different types of documents in different collections , This can improve index utilization ;
• It is recommended not to store long strings , If this field is a query condition , Then make sure that the value of the field does not exceed 1KB, because MongoDB Index only supports 1KB Fields within ;
• It is recommended that if the business is insensitive to the case of stored data , Then use all uppercase / Lower case storage （ Or add an auxiliary field with uniform case ）;
• It is not recommended to use array fields as query criteria ;
• In the consent document , A key with the same name cannot exist ;

Excerpt from 《NoSql Database technology and application 》 Black horse programmer Huang,