Database Migration

Overview

Outline

• A database migration is a change to the structure of a database
  • Versus a change to its contents
• Use tools like sqitch to manage these
• Each change has three parts
  • Forward: make the desired change
  • Check: make sure it happened
  • Backward: undo it (after checking that it was done)
• migrate.py looks for files with structured names
  • Forward: NN_fwd_mnemonic.sql (NN is sequence number, mnemonic is long meaningful name)
  • Check: NN_check_mnemonic.sql
  • Backward: NN_bwd_mnemonic.sql
• Example
  • ../migrations/01_fwd_add_roles_permissions.sql
  • ../migrations/01_check_add_roles_permissions.sql
  • ../migrations/01_bwd_add_roles_permissions.sql
• Keep these files in version control