Overview of the courseware_studentmodulehistory Changes#
This topic provides background information about the
courseware_studentmodulehistory table and why a new database configuration
is needed.
For procedures about how to upgrade all Open edX instances that follow master, see Procedures for Replacing courseware_studentmodulehistory.
Note
The changes described in this section are a part of the upgrade to the Open edX Eucalyptus release.
What Is the courseware_studentmodulehistory Table?#
The courseware_studentmodulehistory database table contains a record for
each attempt that learners make to answer problem types that are implemented in
the edX platform by the capa_module XBlock correctly. This database table
is a standard Django model. It has an id column with a type of 32-bit
signed integer, and therefore has a maximum capacity of 2,147,483,647 records.
What Is the Issue?#
Typically, courseware_studentmodulehistory is the largest table in the
database. It can be twice as large as the next largest table,
courseware_studentmodule.
On the edx.org site, two records are written to this table every second. Before this table for edx.org reached even half of its maximum capacity, edX began to design a replacement with a higher capacity form.
What Is the Replacement Table?#
The new database table,
coursewarehistoryextended_studentmodulehistoryextended, uses a custom
Django field type to give the id column a type of 64-bit unsigned integer,
which offers an exponentially larger storage capacity than the
courseware_studentmodulehistory table.
Why Is A New Database Needed?#
By design, the coursewarehistoryextended_studentmodulehistoryextended table
must be created in a new database, edxapp_csmh. The new database will
coexist alongside the existing edxapp database.
Depending on your operational needs, you can either create this database in your existing database infrastructure or stand a new database server up.
EdX chose to set up a new database to address several requirements.
Distribute write load across different backends.
Reclaim storage on our main database instance, shifting that storage to a less powerful and less expensive system.
Enable smaller, faster, and less disruptive backups.
Ensure faster disaster recovery by having smaller backups.
The edx-platform repository master branch writes records to this database and table as of 5 May 2016.