PostgreSQL Errors During Large Data Migrations In `after_release`

[dleve123]

cc: @fancyremarker

When running a large data migration on our Rails app we received a cascade of postgreSQL related errors when running migrations in the after_release context as defined in .aptible.yml:

1. PG::ConnectionBad: PQconsumeInput() server closed the connection unexpectedly,
2. PG::ConnectionBad: PQsocket() can't get socket descriptor: ROLLBACK * 2,
3. PG::ConnectionBad: PQsocket() can't get socket descriptor,
4. ActiveRecord::StatementInvalid: PG::ConnectionBad: PQconsumeInput() server closed the connection unexpectedly,
5. NoMethodError: undefined method 'result_error_field' for nil:NilClass (related to Rails' postgres adapter)

The migration run failed in the same way twice. The migration was successful when ran manually via aptible ssh rake db:migrate.

[dleve123]

@fancyremarker 👍 on another large migration – has anyone else reported something similar?