MongoDB 的 Index 種類

Percona 的人寫了一篇簡單的文章介紹 MongoDB 的 Index:「MongoDB Indexing Types: How, When and Where Should They Be Used?」。

官方文件的「Indexes」算清楚,不過有些地雷沒講,像是 Unique Indexes 只這樣說:

The unique property for an index causes MongoDB to reject duplicate values for the indexed field. Other than the unique constraint, unique indexes are functionally interchangeable with other MongoDB indexes.

但 Percona 的人就有說出「地雷」,算是不錯的補充教材 XDDD

Unique indexes work as in relational databases. They guarantee that the value doesn’t repeat and raise an error when we try to insert a duplicated value. Unique doesn’t work across shards.

話說前陣子聽到傳言抱怨,MongoDB 的文件是行銷 & 團隊寫出來的,一堆限制都沒寫在明顯的地方... XD

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