[5pt] Constraints

[art-dr]

Related dev. issue(s): tarantool/tarantool#6436

Product: Tarantool
Since: 2.10.0
SME: @ alyapunov

Details

https://docs.google.com/document/d/1EtqfFSIMi6fDqj2y-9WgpunkHsszU65p6LfNly5E9Ag/

Space constraints are needed to ensure that tuples in a space satisfy the specified conditions. Normal constraints define a function that defines the correctness of a tuple. Foreign keys describe the relationship between tables by requiring an external tuple in another spacer with specific fields.

The usual constraints are set for a tuple field or the entire tuple and refer by name to a function from space _func. To be safe for now, it's made to be a Lua function, with the body text right in the _func space.

Constraints for fields work much faster, constraints for tuples are much more versatile.

Definition of done

• describe how constraints for fields work
• describe how constraints for tuples work

[pgulutzan]

@arctic-dreamer: Why is there an sql label? Tarantool issue 6436 appears to be a Lua issue.

[Totktonada]

I see nothing about constraints in the API description: https://www.tarantool.io/en/doc/latest/reference/reference_lua/box_schema/space_create/. It is nice to have guides, but an API reference is more important.

[p7nov]

I see nothing about constraints in the API description: https://www.tarantool.io/en/doc/latest/reference/reference_lua/box_schema/space_create/. It is nice to have guides, but an API reference is more important.

You're right, the reference somehow slipped out of this task's scope. And the same for foreign keys (#2628). Thanks for noting this.
However, I think a new issue will be easier to plan and track. I'll file it and link to this one.