# Postgres plugin

This module implements a Postgres implementation of the micro store interface. 

## Implementation notes

### Concepts
We maintain a single connection to the Postgres server. Due to the way connections are handled this means that all micro "databases" and "tables" are stored under a single Postgres database as specified in the connection string (https://www.postgresql.org/docs/8.1/ddl-schemas.html). The mapping of micro to Postgres concepts is:
- micro database => Postgres schema
- micro table => Postgres table

### Expiry
Expiry is managed by an expiry column in the table. A record's expiry is specified in the column and when a record is read the expiry field is first checked, only returning the record if its still valid otherwise it's deleted. A maintenance loop also periodically runs to delete any rows that have expired.