Use PostgreSQL as default Dragonfly data store

[hmans]

Let's get rid of the immediate S3 dependency and make Dragonfly store its uploaded assets in the database instead.

• Re-evaluate dragonfly-activerecord, it may be good enough.

Otherwise:

• Check how well ActiveRecord copes with bytea columns.
• If there are no immediate problems, create an AR model class to store a single asset (using bytea.)
• Write a custom Dragonfly data store that uses this model to store the binary data, using the model ID as the Dragonfly UID.

Bonus points:

• Migrate existing data on pants.social to this new data store?

[KlausTrainer]

Just out of curiosity: Why not use PostgresDataStore?

[hmans]

It generally works fine, but has one drawback: when dealing with LOs, PostgreSQL has a native ID type (was it oid?) to reference these, and ActiveRecord doesn't understand it (without major hackery). This may not sound like a big problem, since I could just use integer columns instead (OIDs are integer values), however: when you dump your database and then re-import that dump (think: loading a backup after a database failure), these OIDs will change. Oops! The native oid column takes this into account and would automatically change to the new values, but of course stand-alone Integer columns would not. To cut a long story short: I would make dump-based backups unusable, and this, of course, if a big problem.

[KlausTrainer]

Thanks for the background information :)

[matfiz]

@KlausTrainer @hmans Rails supports now OID data type, just do in migration:
t.column :column_name, :oid, null: false
I have not faced any problems during db backup/recovery.

[KlausTrainer]

@matfiz Great :) Thanks for giving notice!