pub use crate::relation_and_scalar::ProtoColumnName;
pub use crate::relation_and_scalar::ProtoColumnType;
pub use crate::relation_and_scalar::ProtoRelationDesc;
pub use crate::relation_and_scalar::ProtoRelationType;


The name of a column in a RelationDesc.
The type of a Datum.
Expression violated not-null constraint on named column
A description of the shape of a relation.
The type of a relation.



This method exists solely for the purpose of making ColumnType nullable by default in unit tests. The default value of a bool is false, and the only way to make an object take on any other value by default is to pass it a function that returns the desired default value. See