Couldn't you store the exported database as sql commands? I'm not familiar with every git hook, but if there aren't enough to automated that I guess you could wrap it.

The slowness of destroying a whole database and then recreate it when checking out should be something you can handle by relying on the diff to generate a series of delete commands and a series of insert commands.

But yeah, I guess committing will be slow if you have a lot of data to export. For the time being, it's a trade off to be made.

[I might consider testing this with my current database project. But I'm using SQLite so I guess that implies a lot less data than Postgres.]