Support passing existing connections

[idomic]

The initialization locks the context to a specific engine. See example

We'd like to allow users to connect to an engine directly by reference (similar to SQL alchemy).

[idomic]

Another great example of this use case (this was solved via the Duckdb team)

[edublancas]

I'm thinking something like this:

from sqlalchemy import create_engine

engine = create_engine("...")

Then:

%sql $engine

IPython supports variable expansion via $var, but I'm unsure if this will pass the actual object or only its string representation.

[edublancas]

It's a bit unclear to me the original issue in the ipython-sql repo. I don't understand if the user wants to re-use an existing engine (what I described in the comment above). Or they want to re-use an engine they created with %sql for later queries. Maybe we can ask him and bring the conversation here?

[idomic]

I think that's the first option.
@machow thoughts?
@Alex-Monahan tagging you since you had the same issue a while ago (it might happen again with new DBs)

[idomic]

I think this one will also be solved once an engine can be passed dynamically? @zzFluke

[Alex-Monahan]

This is still a nice and helpful feature, even if DuckDB can already read dataframes without it! One use case is if you store your dataframes in a dict, you would want to be able to register them with DuckDB (since it won't find them djrectly anymore).

[idomic]

@Alex-Monahan thanks for the feedback! Do you think it's related to this issue or a completely new one?

[Alex-Monahan]

The ability to either pass in an engine or refer to the engine variable and call a function directly on the connection would work in this case. I think that is what this proposes, but I am not certain!

[idomic]

Awesome, yes it is!

[edublancas]

hey @Alex-Monahan, @machow, this has been fixed!

Available in version 0.5.1. Docs here.

Let us know if you have any issues/feedback!

[idomic]

fyi: @pfmoore @gwerbin @rehno-lindeque @ellisonbg @ckald

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