The four constraint kinds every engine understands.
EXCLUDE is PostgreSQL-only, and several dialects declare a four-member type
because that is genuinely all they accept. Widening those to the full enum
would let ConstraintType.Exclude type-check its way into a MySQL builder
that cannot emit it, so they take this instead — the same enum, minus the
member they do not support.
The four constraint kinds every engine understands.
EXCLUDEis PostgreSQL-only, and several dialects declare a four-member type because that is genuinely all they accept. Widening those to the full enum would letConstraintType.Excludetype-check its way into a MySQL builder that cannot emit it, so they take this instead — the same enum, minus the member they do not support.