feat: add --pre-plan-file flag

[aleclarson]

Description

Add --pre-plan-file argument. It should point to a SQL file. Its statements are executed before the migration plan statements.

Motivation

This is particularly useful for settings (e.g. SET statements) that need to be applied before the migration plan. I'm especially interested in running SET check_function_bodies = off; as suggested in #129 (comment).

Testing

None yet.

Notes

You have my permission to take this PR and run with it! :)

[CLAassistant]

All committers have signed the CLA.

[aleclarson]

I've tested this locally and it's working as expected :)

edit: Eh, hold on a sec...

[bplunkett-stripe]

In order to get this to pass plan validation, you will need to wire it through the plan generator as well (into the library and not just the CLI). I can also try to pick this up later if you can wait a bit.

[aleclarson]

I have it running the pre-plan file on the temp DB now as well. For some reason, even after SET check_function_bodies = off; is executed, the function is still being checked (and therefore failing with type "foo" does not exist (SQLSTATE 42704) as it did before.

[aleclarson]

I won't have time to finish this one

[bplunkett-stripe]

Just wanted to double check this isn't blocking you from using the tooling. In in the interim, skipping plan validation should work?

[aleclarson]

@bplunkett-stripe Can't say for sure. I ended up taking a totally different approach that involves parsing the SQL myself, doing a topological sort, creating any objects that don't yet exist, and only then do I call pg-schema-diff (with plan validation disabled). This is working well for me, which means the pre-plan file is no longer needed --in my case--.

[bplunkett-stripe]

@bplunkett-stripe Can't say for sure. I ended up taking a totally different approach that involves parsing the SQL myself, doing a topological sort, creating any objects that don't yet exist, and only then do I call pg-schema-diff (with plan validation disabled). This is working well for me, which means the pre-plan file is no longer needed --in my case--.

Ahh okay. I'm sorry you had to create that kind of work around!