Database transaction differences: the difference between committable reads and repeated reads

This article comes from my own blog: http://www.wangerbao.com/?p=279

The default thing for Mysql is Repeatable Read Isolation Level.

The default thing for PostGres is to Read Committed Isolation Level. Now compare their differences based on examples.

Mysql:

Things 1 on the left and 2 things on the right.

Step one:

Thing 1 query, thing 2 query, their query results are the same.

Step 2:

Thing 1 update-query-but do not submit, thing 2 query, their results are inconsistent

Step 3:

Thing 1 submission-query, thing 2 query, their results are inconsistent-in fact, this is the difference between the two things.

Step 4:

Thing 1 query, thing 2 submit-query, their results are the same

Postgresql:

Things 1 on the left and things 2 on the right

Step one:

Thing 1 query, thing 2 query, query results are consistent.

Step 2:

Thing 1 modification-query, thing 2 query, query results are inconsistent

Step 3:

Thing 1 submission-query, thing 2 query, query results are consistent

Step 4:

Thing 1 query, thing 2 submit query, the result is consistent, no screenshot