cstore_fdw 介绍
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：
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压缩: Reduces in-memory and on-disk data size by 2-4x. Can be extended to support different codecs.
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列预测: Only reads column data relevant to the query. Improves performance for I/O bound queries.
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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：
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Support for 40+ Postgres data types. The user can also create new types and use them.
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Statistics collection. Postgresql’s query optimizer uses these stats to evaluate different query plans and pick the best one.