* Optimize reactions table
Change reactions primary key to (PostId, UserId, EmojiName) so fetching
reactions for post will use primary key lookup instead of table scan.
* fix db version
* review fixes
* update database schema in scripts/
* [MM-13341] Add an upgrade test to verify schema
Upgrade test is done by following steps:
1. A mysql dump generated from v4.10.0 is imported in a database and is ran through migration code
2. Another fresh database is generated without any initial data, which gets latest schema.
3. Diff between these 2 databases is generated using mysqldiff tool from mysql utilities
For db setup, version cli command is used which takes care of migration or setup of fresh db
* Using 5.7 tag for mysql docker image which is already used for db setup
* Starting docker containers for db before running tests
* Using db from v5.0.0 for migration test
* Added migration test for psql and made some improvements in running commands in docker
* Add postgres db dump file
* Updated message
* moved dump files to scripts and using error code from diff command
