Google Cloud Spanner support

[amacneil]

Need to add support for Google Cloud Spanner

[AJCStriker]

Hey @amacneil I would be interested in picking this issue up and submitting a PR.

I took a look at the current drivers but is there anything to keep in mind whilst designing an integration? In particular clarification about how you view Connection lifecycles would be really helpful?

[amacneil]

Last time I looked into this, I ran into the issue that dbmate has been designed around an assumption that all drivers will use database/sql, and the spanner driver did not use that. So it would require refactoring the driver interface to remove dependence on database/sql.

Long term I think this is a good direction to take dbmate, but just be aware that to achieve this feature I think you will need to refactor the interface and all other drivers to match the new interface, it won't be a simple case of adding one new driver.

From memory there also might be a problem with the spanner driver not accepting multiple sql statements in one string, so we will need to import a sql parsing library and do our own statement splitting. Again I think this is a nice feature that would benefit all drivers eventually (allowing us to give more helpful error messages, etc), but it adds complexity.