The beauty of indexes is that they can be used with multiple keys. A single key index can be thought of as a table with one column. A multi-key index or compound index can be visualized as a multi column table where the first column is sorted first, and then the next, and so on. In this recipe, we will look at how to create a compound index and examine how it works.
Load the sample dataset and create an index on the city field, as described in the previous recipe.
- Assuming you have already created an index on the
cityfield, create one by executing the commanddb.mockdata.createIndex({'city': 1})again. - Run a
find()query:
> plan = db.mockdata.find({city:'Boston', first_name: 'Sara'}).explain("executionStats")- Examine the
executionStats:
> plan['executionStats']You should see the following result:
{ "executionSuccess" : true, "nReturned" : 1, "executionTimeMillis" : 0, "totalKeysExamined" : 9, "totalDocsExamined" : 9,...