Looking back at the development history of relational databases since they were widely used, the transition from independent architecture to distributed architecture is undoubtedly a key transition, which is driven by emerging business needs and explosive growth in data volume.
On the one hand, a larger amount of data breeds more possibilities for social and economic development. On the other hand, better database performance is required to suppress operation and maintenance costs and new failures that may be brought about by the addition of storage nodes. Therefore, making the operation of distributed databases as transparent as independent databases is one of the keys to improving user experience oltp database.
As a frequent operation in database operation and maintenance, DDL operations should be transparent to business developers and operation and maintenance engineers.
Front-line operation and maintenance engineers often say:
"DDL operations can only be done late at night."
"Execution of DDL statements takes a lot of time, sometimes weeks."
If the database can perform efficient and transparent DDL operations, that is, DDL statements are executed quickly and do not interfere with other business development or operation and maintenance tasks, they may not have such an embarrassing experience.
In this article, we will introduce how OceanBase 4.0 implements efficient and transparent DDL operations, and introduce the characteristics and design ideas of new DDL operations in OceanBase 4.0 from the following perspectives:
1. Which DDL operations are more user-friendly?
2. How does the OceanBase database implement high-performance DDL operations?
3. What are the new changes in the DDL operation of OceanBase database V4.0?
4. Added DDL operation test in OceanBase database V4.0
Which DDL operations are more user-friendly?
To answer this question, we need to understand the concept of DDL operations.
In addition to DML statements that directly manipulate data (such as SELECT, INSERT, UPDATE, DELETE, etc.), database operation and maintenance also involves other statements, such as CREATE, ALTER, DROP, TRUNCATE, etc. Related to data definition. The latter type of statement is called a DDL statement. For example, adding a column to a table and adding an index to a column are two everyday DDL operations.
In the early days of database development, the execution of DDL statements was considered one of the most expensive database operations because DDL operations would render tables unreadable and block tasks that were in progress at the time. Executing DDL statements on a table with a large amount of data will cause the database service to be blocked for a long time, which is unacceptable for critical businesses that need to be online all the time. Therefore, Online DDL was introduced to keep user requests alive while executing DDL statements. So far, most Online DDL-based databases on the market do not make DDL operations completely transparent to users.