In PostgreSQL, the adding and dropping a column is an instant ddl(This name seems only to be used in mysql, but I like it). In this article, I try to explain the implement of that. The reference: https://www.postgresql.org/docs/current/sql-altertable.html Basic Concepts instant ddl For a table with $n$ tuples, if a ddl post can be performed in time $O(1)$ ,we call this ddl instant. So to implement an instant ddl, the data organization must remain unchanged....

Overview In application level, ”PostgreSQL“ has native supports for using SSL connections. This requires that OpenSSL is installed on both client and server systems and that support in PostgreSQL is enabled at build time. With SSL, we can: Encrypted data on Internet transmission Allow client to authorize the server(PostgreSQL), which can protect the client from connecting to the attacker’s server Allow server to authorize the client, which can stop the attacker from connecting to the database even if password leak....

sequence type background From official documents: 9.17. Sequence Manipulation Functions CREATE SEQUENCE Sequence objects are special single-row tables created with CREATE SEQUENCE. Sequence objects are commonly used to generate unique identifiers for rows of a table. The sequence functions, provide simple, multiuser-safe methods for obtaining successive sequence values from sequence objects. Main function There is no much concerns about these functions nextval Advances the sequence object to its next value and returns that value setval...

Abstract a protocol for schema evolution in a globally distributed database management system with shared data, stateless servers, and no global membership. asynchronous all servers can access and update all data during a schema change INTRODUCTION Schema evolution: the ability to change a database’s definition without the loss of data F1 is built on top of Spanner, a globally distributed KV data store Main feature The main features of F1 that impact schema changes are:...

Primitive Operation if Transactions There are three address spaces that transaction interact in important ways: The space of disk blocks holding the database elements. The memory address space managed by buffer manager. The local address space of the transaction. To describe a transaction, we need some operation notions:(X below is a database element while t is a local varible, and we suppose a database element is no larger than a single block)...