sqlite3 support

[hexylena]

@hujambo-dunia asked me recently about sqlite3 support. While on a meeting today I took a look at what that would require by running a few of the most commonly used queries just piped straight to sqlite3 rather than integrated properly, just to see what it would look like.

gxadmin echoquery queue-detail | sqlite3 database/universe.sqlite

This query doesn't work for two reasons that are relatively fixable (or solved via a sed pre-query execution)

• Cast to text datatype is done (that's really unnecessary and should be removed but in other places it is necessary)
• at time zone 'utc' is not valid in sqlite3, and is heavily used in gxadmin to get proper current times

And on that isn't really as fixable:

• We use unsupported joins ("RIGHT and FULL OUTER JOINs are not currently supported")

maybe it could be rewritten to avoid those, but it seems like a fair bit of work to make this speak two dialects of sql without an ORM. While it is probably theoretically possible, in practice I think it would be quite difficult and not worth the ROI as this tool focuses on production use.

But I'm opening the discussion in case people want to comment on this or provide their ideas for working around these issues.

[hexylena]

I've added experimental support in case anyone wants to use it

GXADMIN_EXPERIMENT_SQLITE3=1 ./gxadmin query users-total              
1

but expect it to fail and not behave at all how you'd expect. echoquery in addition will not give you the real query that's being executed, but maybe it's useful for someone.