Function insert_target_columns 

pub fn insert_target_columns(
    catalog: &dyn MutationPrivilegeCatalog,
    stmt: &InsertPlan,
) -> Result<Vec<String>, SQLError>

The columns an INSERT supplies, as PostgreSQL records them in its target’s insertedCols: the columns it names, or else the leading columns of the table, one for each value a row supplies; DEFAULT VALUES supplies none.