MongoDB for Developers with Python Transcripts
Chapter: High-performance MongoDB
Lecture: Concept: Indexes via the shell
Login or
purchase this course
to watch this video and the rest of the course contents.
0:01
We've seen how powerful adding indexes to MongoDB is
0:04
and I talked a little bit how the nested nature of these documents means
0:09
there's naturally fewer primary keys,
0:11
so there's fewer on average actual indexes
0:15
that get created just as part of working with the database;
0:18
so creating these indexes is even more important in document databases
0:22
than it is in relational databases.
0:24
So here we are in the shell, this would be Robomongo
0:27
or just the Mongo command line interface
0:30
and we can create an index on a collection by saying db.collection name
0:33
so here we have cars.createIndex
0:35
and then we pass it two things, first one required, second one optional
0:39
we pass it the actual fields we want to create the index on;
0:44
so here we have service_history.customer_rating
0:48
so we could traverse this hierarchy if necessary
0:51
we just use that dot like we have been in the shell the whole time
0:55
and then we say one or minus one,
0:57
so do you want to sort ascending or descending.
0:59
And this mostly matters for either what you might consider the natural sort
1:03
or if you're doing a composite key or a composite index
1:08
and that composite index is being used for sorting on both fields
1:12
and all the orders have to line up exactly for the sort to use that index.
1:17
Then we can pass additional information,
1:19
here we have background as true and the name,
1:21
I like to name my indexes if I'm doing this shell
1:24
because then it's easier to see like okay why did I create this index
1:28
here we want the customer ratings of service,
1:31
so that's pretty nice, background true, that's not the default
1:35
but that means it will run basically in the background
1:38
without blocking the database operations,
1:41
if you don't put that, when you hit go
1:43
the database will stop doing any sort of database stuff
1:46
until this index is generated so be aware.
