mongo_indexes.md

These are the indexes each mongo db should have in order to perform well. Each section states the collection name and then the indexes. To create an index, you'll typically either use the mongohq type web interface or a standard terminal console. If a terminal, this assumes you've logged in and gotten to the mongo prompt

mongo mydatabasename

If using the terminal, to add an index to a collection, you'll need to prefix ensureIndex with

db.collection_name

as in db.location_map.ensureIndex({'course_id': 1}{background: true})

location_map:

ensureIndex({'org': 1, 'offering': 1})
ensureIndex({'schema': 1})

fs.files:

Index needed thru 'category' by _get_all_content_for_course and others. That query also takes a sort which can be uploadDate, display_name,

ensureIndex({'_id.tag': 1, '_id.org': 1, '_id.course': 1, '_id.category': 1})

Remove index on displayname

modulestore:

Mongo automatically indexes the _id field but as a whole. Thus, for queries against modulestore such as modulestore.find({'_id': {'tag': 'i4x', 'org': 'myu', 'course': 'mycourse', 'category': 'problem', 'name': '221abc', 'revision': null}}) where every field in the id is given in the same order as the field is stored in the record in the db and no field is omitted.

Because we often query for some subset of the id, we define this index:

ensureIndex({'_id.tag': 1, '_id.org': 1, '_id.course': 1, '_id.category': 1, '_id.name': 1, '_id.revision': 1})

Because we often scan for all category='course' regardless of the value of the other fields:

ensureIndex({'_id.category': 1})

Because lms calls get_parent_locations frequently (for path generation):

ensureIndex({'_id.tag': 1, '_id.org': 1, '_id.course': 1, 'definition.children': 1})

Remove these indices if they exist as I can find no use for them:

 { "_id.course": 1, "_id.org": 1, "_id.revision": 1, "definition.children": 1 }
 { "definition.children": 1 }

NOTE, that index will only aid queries which provide the keys in exactly that form and order. The query can omit later fields of the query but not earlier. Thus modulestore.find({'_id.org': 'myu'}) will not use the index as it omits the tag. As soon as mongo comes across an index field omitted from the query, it stops considering the index. On the other hand, modulestore.find({'_id.tag': 'i4x', '_id.org': 'myu', '_id.category': 'problem'}) will use the index to get the records matching the tag and org and then will scan all of them for matches to the category.

To find out if any records have the wrong id structure, run

db.fs.files.find({uploadDate: {$gt: startDate, $lt: endDate},
       $where: function() {
           var keys = ['category', 'name', 'course', 'tag', 'org', 'revision'];
           for (var key in this._id) {
               if (key != keys.shift()) {
                   return true;
               }
           }
           return false;
       }},
       {_id: 1})

modulestore.active_versions

ensureIndex({'org': 1, 'offering': 1})

modulestore.structures

ensureIndex({'previous_version': 1})

modulestore.definitions

ensureIndex({'category': 1})