1. 卡桑德拉：
Cassandra 是一个免费、开源、分布式、广泛的列存储、NoSQL 数据库管理系统。它由 Apache 软件基金会开发，最初于 2008 年 7 月发布。Cassandra 旨在处理跨多个商用服务器的大量数据，提供高可用性且无单点故障。
2. PostgreSQL :
PostgreSQL 是一个强大的开源对象关系数据库系统。由于其高稳定性，它以低维护工作提供良好的性能。 PostgreSQL 是第一个实现多版本并发控制 (MVCC) 功能的 DBMS。
Cassandra 和 PostgreSQL 的区别：
| S.NO. | CASSANDRA | POSTGRESQL |
|---|---|---|
| 1. | Developed by Apache Software foundation and released on July 2008. | Developed By PostgreSQL Global Development Group on 1989. |
| 2. | It is wide-column store based on ideas of BigTable and DynamoDB. | It is widely used open source RDBMS. |
| 3. | Cassandra is written in Java languages. | PostgreSQL is written in C languages. |
| 4. | The primary database model for Cassandra is Wide column store. | The primary database model for PostgreSQL is Relational DBMS. |
| 5. | It has no Secondary database models. | It has Document store as Secondary database models. |
| 6. | Server operating systems for Cassandra are BSD, Linux, OS X and Windows. | Server operating systems for PostgreSQL are FreeBSD, HP-UX, Linux, NetBSD, OpenBSD, OS X, Solaris, Unix and Windows. |
| 7. | It does not support XML format. | It supports XML format. |
| 8. | It supports Secondary indexing but in a restricted way, i.e., only equality queries, not always the best performing solution. | It supports Secondary indexing. |
| 9. | It does not supports Server-side scripting. | It has user defined functions for Server-side scripts. |
| 10. | It supports selectable replication factor method. | It supports Master-master replication method. |
| 11. | In Cassandra, partitioning can be done Sharding. | In PostgreSQL, partitioning can be done by range, list and hash. |
| 12. | It offers an API for user-defined Map/Reduce methods. | It does not offers an API for user-defined Map/Reduce method. |
| 13. | Cassandra does not provides the concept of Referential Integrity. Hence, no Foreign Keys. | PostgreSQL provides the concept of Referential Integrity and have Foreign keys. |