Upsert aka On Conflict Do Update

[bh2smith]

Introducing INSERT ... ON CONFLICT ... DO UPDATE!

This works well but also requires primary key or, more loosely, a uniqueness constraint on the table in question.
We have insightful error messaging that will literally print out the table alterations require for the provided conflict_columns:

So, when table exists without index we will see this error log suggesting how to fix the issue.

The ON CONFLICT clause requires a unique or exclusion constraint on the column(s): hash. Please ensure the table 'results_4238114' has the necessary constraint.To fix this, you can run the following SQL command:
ALTER TABLE results_4238114 ADD CONSTRAINT results_4238114_hash_unique UNIQUE (hash);

Note that, additionally, the table does not need to exist first. It will be created without any validation on the uniqueness constraints at first run. We only validate the uniqueness at the first time of actual upsert.

Test Plan

For now this is

1. Run it

docker-compose up -d
make run

If you already have the table (from previous runs) you will hit the error above.
Execute the suggested ALTER TABLE command and try again!

UPDATE:
There are now "unit" tests of all conflict column validation and upsert method works as expected.

Closes #56.

[mooster531]

I think that if we're using an ORM, we should use the ORM as much as we can :) I simplified the upsert function using sqlalchemy's built-in "on conflict update" utility.

[bh2smith]

I think your comments have all been addressed.

[mooster531]

🚀🚀🚀