Postgresql 中文操作指南

67.1. Introduction #

PostgreSQL 包含标准 btree（多路平衡树）索引数据结构的实现。任何可以按明确的线性顺序排序的数据类型都可以通过 btree 索引编制索引。唯一的限制是索引项不能超过一页的三分之一（如果适用，在 TOAST 压缩后）。

PostgreSQL includes an implementation of the standard btree (multi-way balanced tree) index data structure. Any data type that can be sorted into a well-defined linear order can be indexed by a btree index. The only limitation is that an index entry cannot exceed approximately one-third of a page (after TOAST compression, if applicable).

因为每个 btree 运算符类都对其数据类型施加排序顺序，所以 btree 运算符类（或实际上是运算符族）已成为 PostgreSQL 对排序语义的通用表示和理解。因此，它们获得了一些超出仅支持 btree 索引所需的功能，并且与 btree AM 相距甚远的系统部分会使用它们。

Because each btree operator class imposes a sort order on its data type, btree operator classes (or, really, operator families) have come to be used as PostgreSQL’s general representation and understanding of sorting semantics. Therefore, they’ve acquired some features that go beyond what would be needed just to support btree indexes, and parts of the system that are quite distant from the btree AM make use of them.