notes.txt

FK creation should be in 2 steps
- Add invalid FK with short timeouts
- Validate FK concurrently with long timeouts
FKs should always be named
Indexes should always be named
Indexes should always be btrees
Index creation should be concurrent and isolated, with large lock/statement timeout
Index creation should not occur in a transaction
Every other DDL change should occur in a transaction
Columns added to existing tables must always specify NULL
New columns must never specify a default
  https://www.postgresql.org/docs/9.4/static/ddl-alter.html
  Adding a column with a default requires updating each row of the table
  (to store the new column value). However, if no default is specified,
  PostgreSQL is able to avoid the physical update. So if you intend to fill
  the column with mostly nondefault values,it's best to add the column with no
  default, insert the correct values using UPDATE, and then add any desired
  default as described below.