mongoDb:找不到索引来验证连接字段是否唯一

Question

嘿，我需要合并我的两个集合，但是 mongo 返回“找不到索引以验证连接字段将是唯一的”

1.创建唯一索引2.删除whenMatched/whenNotMatched

db.getCollection("GeoLite2-City-Blocks-IPv4").aggregate([
    {$match:{longitude:{$gt:175,$lt:180}}},
    {$merge:{
        into:"GeoLite2-City-Locations-ja",
        on:"geoname_id",
        whenMatched: "replace",
        whenNotMatched: "insert" 
    }}
])

预期:retuns GeoLite2-City-Blocks-IPv4 include GeoLite2-City-Locations-ja

Answer 1

$merge 聚合阶段需要 unique index on the identifier fields :

$merge requires a unique, index with keys that correspond to the on identifier fields. Although the order of the index key specification does not matter, the unique index must only contain the on fields as its keys.

对于您的操作，需要在包含字段 geoname_id 的 GeoLite2-City-Locations-ja 集合中存在一个唯一索引。