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Calen Pennington 0d88379eeb Make course ids and usage ids opaque to LMS and Studio [partial commit]

This commit adds all of cms.

These keys are now objects with a limited interface, and the particular
internal representation is managed by the data storage layer (the
modulestore).

For the LMS, there should be no outward-facing changes to the system.
The keys are, for now, a change to internal representation only. For
Studio, the new serialized form of the keys is used in urls, to allow
for further migration in the future.

Co-Author: Andy Armstrong <andya@edx.org>
Co-Author: Christina Roberts <christina@edx.org>
Co-Author: David Baumgold <db@edx.org>
Co-Author: Diana Huang <dkh@edx.org>
Co-Author: Don Mitchell <dmitchell@edx.org>
Co-Author: Julia Hansbrough <julia@edx.org>
Co-Author: Nimisha Asthagiri <nasthagiri@edx.org>
Co-Author: Sarina Canelake <sarina@edx.org>

[LMS-2370]

2014-05-07 12:56:43 -04:00

2.7 KiB

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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:

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

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})

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.modulestore.find({$where: function() { 
    var keys = Object.keys(this['_id']); 
    var ref = ['tag', 'org', 'course', 'category', 'name', 'revision']; 
    for (var i=0; i < ref.length; i++) { 
        if (keys[i] != ref[i]) 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})

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