4. Vector and Ingres : Incompatibilities with Ingres Database : Differences in Constraint Checking
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Differences in Constraint Checking
Constraint checking in Vector differs from traditional Ingres in the following ways:
When loading data with COPY, if a constraint violation is detected, the entire dataset is rejected.
When loading data with COPY, Vector detects foreign key (referential) constraint violations, unlike traditional Ingres.
Vector does not handle cyclic constraints.
Because Vector uses the optimistic concurrency control model (see  Transaction Isolation Model), it is possible that a constraint violation is only detected at commit time.