Allow creation of multiple databases

[victorhahncastell]

See amended documentation at https://github.com/victorhahncastell/docker-docs/tree/master/mysql. Matching pull request will go to docker-library/docs

[yosifkit]

This seems a bit complex for an official image and I would rather recommend that a user just write a startup script to creates all the users, databases, and permissions that they need, but I'll defer to @ltangvald since he is from upstream and helps manage these images.

[tianon]

I agree, this is incredibly complex (both the implementation and the user experience).

[victorhahncastell]

Thanks for your feedback! I agree the implementation is a bit complex--it probably shows that I don't write shell scripts every day. I don't quite see though how the user experience is overly complicated, took me three sentences to amend the documentation.

[ltangvald]

I agree the implementation is too complex. User experience seems ok, though ideally we'd have something that isn't any different to use whether you want 1 or more databases (e.g. you supply a delimited list to a single variable). I'll see if I can pick some brains about it (though almost everyone is on vacation at the moment).
If we can't find a clean way to implement it, finding a good solution to issue #24 might be a decent compromise.

[ltangvald]

Is this now adequately solved by the support for running arbitrary init scripts during database creation?

[asymmetric]

I think the answer to @ltangvald's question is yes, this and #18 should be closed since we can drop scripts in /docker-entrypoint-initdb.d.

[victorhahncastell]

Guess I should comment on this as this is my PR -- though I don't really have any opinion on this as my work currently does not involve this project any more. Feel free to close :-)

[yosifkit]

👍

[mrts]

And here's a sample script and README with instructions for creating any number of databases during initialization by mounting a volume into /docker-entrypoint-initdb.d:
https://github.com/mrts/docker-posgresql-multiple-databases