MIGRATION

The database flavours:

• RDBMS
• document
• object

The shape of a migration

[tbd]

Timelines

• schema is always mutable (datamic an exception)

Complicated migrations

Small example (datatype, MySQL version fix, and default data):

+BEGIN_SRC

-- fix the MODIFIED column so it defaults to a sensible value

• -- (this column is deprecated but still fails when the defaults are used in inserts)

• ALTER TABLE merchants MODIFY COLUMN MODIFIED timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP;

• -- (this column is deprecated but still fails when the old string defaults are used in inserts)

• ALTER TABLE merchants MODIFY COLUMN MODIFIED timestamp NULL;

  UPDATE merchants SET MODIFIED = CREATED where MODIFIED = '0000-00-00 00:00:00';

  +END_SRC

Big example:

[tbd]

Non-schema modification