MongoDB .explain("executionStats") shows keysExamined of something around 103,000 but I cant find out what it means.

CodePudding user response：

From MongoDB docs:

explain.executionStats.totalKeysExamined

Number of index entries scanned. totalKeysExamined corresponds to the nscanned field returned by cursor.explain() in earlier versions of MongoDB.

CodePudding user response：

1. This are good news when you have totalKeysExamined > 0 , this mean your query is using index.

2. If you have totalKeysExamined=0 , and totalDocsExamined>0 than you may need to create some indexes.

3. The best case is when you have totalDocsExamined=0 and totalKeysExamined>0 , this is the case when you have the so called "covered query" , this is the fastest case where you search and load only from memory and do not touch the documents from storage.