Support Google Cloud Spanner

[yu-iskw]

Motivation

I transfer Spanner tables to BigQuery using data engineering tools. I would like to make sure if data in BigQuery is completely the same as Spanner.

[sirupsen]

Definitely do-able. The implementor would need to take into account that Spanner only seems to support sha1, but most databases support that, so that shouldn't be a problem.

[github-actions]

This issue has been marked as stale because it has been open for 60 days with no activity. If you would like the issue to remain open, please comment on the issue and it will be added to the triage queue. Otherwise, it will be closed in 7 days.

[github-actions]

Although we are closing this issue as stale, it's not gone forever. Issues can be reopened if there is renewed community interest. Just add a comment and it will be reopened for triage.