Question

We are currently building a PostgreSQL database that allows us to create profiles for hardware. Each profile exists of a few different properties which are all dynamically added to the profile through the UI. Each property can be of a different type (string, integer, text, …)

How would I most efficiently store these properties in a relational database?

I’ve read Storing diverse value types in a database and I’m charmed by the single answer there but I’m not at all confident that this is the ideal solution. Are there any pros/cons using the separate-table-per-type approach over the other solutions? Anyone has real world experience with this and minds shedding some light on the best approach?

Answer 1

My preferred way is single table with both key and value being varchar and/or text.

The only big disadvantage of table-per-type in that comment I can think of is that it’s hard to constraint the uniqueness of the key in pair with the entity this key-value entry belongs to.

Table inheritance (but still with table-per-type) would be another way to go and IMHO it’s brutally type-safe and compliant with postgres and ORM concepts:

CREATE TABLE key_values(user_id integer references users(id), key varchar(255), type varchar(255), CONSTRAINT UNIQUE(user_id, key));
CREATE TABLE key_values_int(value integer) INHERITS (key_values);
CREATE TABLE key_values_string(value varchar(255)) INHERITS (key_values);
and so on...

This perfectly maps to JPA.