cstore_fdw 实现了 PostgreSQL 数据库的柱状存储，用于对批量加载的数据进行分析的场景。
该扩展使用了 Optimized Row Columnar (ORC) 格式的数据存储布局。ORC 提升 Facebook 开发的 RCFile 格式，带来如下好处：
压缩: Reduces in-memory and on-disk data size by 2-4x. Can be extended to support different codecs.
列预测: Only reads column data relevant to the query. Improves performance for I/O bound queries.
跳过索引: Stores min/max statistics for row groups, and uses them to skip over unrelated rows.
此外，我们使用了 PostgreS 外部数据封装 API 和类型呈现，带来：
Support for 40+ Postgres data types. The user can also create new types and use them.
Statistics collection. PostgreSQL’s query optimizer uses these stats to evaluate different query plans and pick the best one.
Simple setup. Create foreign table and copy data. Run SQL.
