The conditions one key of a write condition accepts: everything a query
filter accepts for it, plus null where the attribute is nullable.
dyna-record removes a nulled attribute rather than storing it, so in a write
condition null means "not set" and matches a row where the attribute is
absent (DynamoDB's attribute_not_exists). On an attribute that cannot be
absent it could never match, so it is not offered there. Inside an object
compared whole, null on a nullable field means the same, as it does in a
query filter (see EqualityConditionFor).
The conditions one key of a write condition accepts: everything a query filter accepts for it, plus
nullwhere the attribute is nullable.dyna-record removes a nulled attribute rather than storing it, so in a write condition
nullmeans "not set" and matches a row where the attribute is absent (DynamoDB'sattribute_not_exists). On an attribute that cannot be absent it could never match, so it is not offered there. Inside an object compared whole,nullon a nullable field means the same, as it does in a query filter (see EqualityConditionFor).