A composite type is a product type, not a sum type. PostgreSQL currently has great support for product types, but basically no support for sum types. From the perspective of algebraic data types, this feels like a "missing link" in the type system. I'm not sure why SQL or the underlying relational model has never addressed this deficiency. Would greatly appreciate any insight anyone may have.
On 5/18/23 05:27, Victor Nordam Suadicani wrote: > Hi, > > Is there any nice way to handle sum types (aka tagged unions) in a > PostgreSQL database? I've searched far and wide and have not reached any > satisfying answer. > > As a (somewhat contrived) example, say I have the following enum in Rust: > > enum TaggedUnion { > Variant1(String), > Variant2(i32), > Variant3(f64), > } >
> If there are no good methods of handling this, is there any way > PostgreSQL could be extended with capabilities for this? I have no idea > how this would be done in practice though. Perhaps SQL itself is just > unsuited for data of this kind? I don't really see why it should be though.
