Flyway postgres squash script

Script to squash flyway migrations to a single migration file based on the current schema of a postgres database. Feel free to extend or copy and paste this script into your own projects!

This script is based on: https://medium.com/att-israel/flyway-squashing-migrations-2993d75dae96.
Please read this article before continuing.

In short: we wish to squash a lot of SQL files into one 'baseline' SQL file, basically starting flyway fresh again. To do so we will have to generate a squashed migration file and create the flyway_schema_history table from scratch on every database environment flyway already ran on.

In this script you can run two steps:

1. Creating a squashed migration (Create and Delete step from the article). This will delete all the SQL files in the current directory and create a schema-only dump with pg_dump.
2. Preparing a database for the squashed migration (Rename step from the article). This will rename the flyway_schema_history table, so that flyway can be ran afterwards with the squashed migration file to create a new flyway_schema_history table.

NOTE you will probably have to execute step 1 once and you will probably have to execute step 2 multiple times, for each database environment that already ran flyway.

NOTE it is assumed you run the Baseline step (actually running flyway) from the article separately from this script (with for instance spring data on start-up of your application or with maven).

NOTE this Baseline step (actually running flyway) should be done shortly after running step 2 to prevent for instance an application restart searching for a non existing flyway table.