The Growth team is moving the mentor/mentee relationship to a database table in extension1, called `growthexperiments_mentor_mentee`.
==== Information about table size
Answers questions from https://wikitech.wikimedia.org/wiki/Creating_new_tables.
* Should this table be replicated to wiki replicas (does it contain private data)?: **No**, it should be **private**
* Size of the table/Table growth: the table should never be bigger than the number of rows in `user` (if T227876 gets prioritized, the number of rows there will be doubled)
* Expected amount of queries, both writes and reads: new account creation causes a write; reads are frequent (this information is cached in memcached, and it might be needed on all pageviews by an user with the features enabled)
* Examples of queries that will be using the table:
** `SELECT gemm_mentor_id FROM growthexperiments_mentor_mentee WHERE gemm_mentee_id=XXX`
** `SELECT gemm_mentee_id FROM growthexperiments_mentor_mentee WHERE gemm_mentor_id=XXX`
* Release plan
** This is not a new feature, it is refactoring the storage backend for mentor/mentee relationship to use a dedicated database table. This is to allow softwre to get mentees for a mentor (second example query). We want to make the switch on all our target wikis (see https://github.com/wikimedia/operations-mediawiki-config/blob/master/dblists/growthexperiments.dblist for list) at once, if possible.
==== Table creation
Database should be created for all wikis in [growthexperiments.dblist](https://github.com/wikimedia/operations-mediawiki-config/blob/master/dblists/growthexperiments.dblist). The table should **not** be replicated.
[x] Add to private_tables in Puppet
[ ] Wait for https://gerrit.wikimedia.org/r/c/mediawiki/extensions/GrowthExperiments/+/673999 to get merged
[ ] A deployer creates the database tables