Module variant_key 

Policy for rejecting VARIANT as a key.

Variant equality, hashing and ordering are byte-wise over the canonical encoding and carry no stable SQL semantics, so a variant value must never become a key. DataType::contains_variant is the only predicate; the checks are layered by how much they can be trusted.

Required to be complete, because they inspect the final key definition rather than a plan shape: StreamMaterialize (a table’s, index’s or MV’s own pk) and reject_variant_in_internal_storage_key (every streaming state table pk).

Last line of defense for batch, which has no state tables: reject_variant_keys. It runs after logical optimization so rewrites are already resolved, but it is still shape-based — a new batch operator that keys on a column needs an arm there.

Best-effort: StreamKeyChecker, which names the offending SQL clause early. Whatever it misses is still caught above, only with a less specific message.

Constants

VARIANT_KEY_HINT

Shared hint for every VARIANT-as-key rejection, so a test can assert one stable string regardless of which layer fired.

Functions

variant_key_error

Builds the rejection error so that every layer reports the same shape.