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moneta-rb / moneta

a unified interface to key/value stores
https://github.com/moneta-rb/moneta
MIT License
1.11k stars 87 forks source link

Metadata support #107

Open vlopez opened 7 years ago

vlopez commented 7 years ago

Would it be possible to simply add an expires column to the table definition? Instead of marshalling and adding it somehow into the k/v, just use that col to check if the entry has expired.

Is there some reason why it was not done this way?

asppsa commented 7 years ago

Hi there,

I think you are right that this would be possible -- the mongo adapter does something similar to this. If you feel like contributing a patch that does this, I think it would be gratefully received.

The only gotcha would be providing compatibility for people who have a table created with a previous version -- perhaps a migration, or a fallback for when the column is missing.

asppsa commented 5 years ago

Having had a further think about this, I think the best way to implement this sort of thing would be to allow adapters to indicate that they support a "metadata" feature. The SQL-based adapters can do this via additional columns; the document stores via additional keys, etc. A wrapper class could be provided to give metadata support where the adapter does not support it natively (similar to the existing Expires wrapper). Metadata could include details such as a creation time, update time, user details, geographic details, etc.

Fallback support for expiry (where not natively supported) could then be implemented on top of this metadata functionality. In the SQL adapters, this would ultimately mean that a row's expiry could be stored in a specific column.