Oracle index domain R-tree(B-tree extension)

* [构建域索引](https://docs.oracle.com/en/database/oracle/oracle-database/19/addci/building-domain-indexes.html#GUID-E370B5E4-BAC0-49C6-B17D-830B3A507FB4)

域索引是为专用域（如空间或图像处理）设计的索引。用户可以在设计器创建索引类型后生成给定类型的域索引。域索引的行为特定于行业、业务功能或其他特殊用途;您必须在墨盒开发过程中指定它。

* [Oracle domain index tips](https://www.dba-oracle.com/t_domain_index.htm#:~:text=A%20domain%20index%20is%20actually%20an%20extension%20to,be%20placed%20on%20a%20single%20column%20in%20Oracle.)

An example of the use of domain indexing would be the use of R-tree indexes for spatial data. A domain index is based on the concept of an INDEXTYPE, which, like a User Defined Type (UDT), is created and maintained by the user. In order to use a domain index, a data cartridge that implements its structures, methods, and types must be created. 

* [什么是R树？ - 知乎](https://zhuanlan.zhihu.com/p/62639268)