There exists several schema migration tools from MySQL to PostgreSQL, pgloader as one of the most popular ones.

All off them, as far as I have seen, is designed to be a single shot schema migration tool, so if MySQL schema was changed due to continuous development after pgloader was executed, developers have to sync them to PostgresQL in some kind of manual, or custom-made script. (custom-made script seems like the most common way when I searched it online) Another aspect of the existing ones is that how the schema is migrated tends to be a black box, and the configuration file didn't seem fully customizable to me. For example, you cannot do something like excluding an index for a certain table.

This tool can resolve both cases.

How it works consists of 3 steps:

1. parse MySQL schema into ruby-handleable objects by using rails ActiveRecord

2. combine 1., pre-defined general migration rules, and user-defined dsl to generate a PostgresQL schemafile

3. apply 2. using ridgepole(a common rails schema management tool in japan) to PostgresQL, which checks the diff between 2. and the actual PostgresQL schema and generates/runs the exact DDL necessary to apply