presto-base-jdbc/src/main/java/io/prestosql/plugin/jdbc/TransactionScopeCachingJdbcClient.java/TransactionScopeCachingJdbcClient/dropColumn
class TransactionScopeCachingJdbcClient:    @Override
    public void dropColumn(JdbcIdentity identity, JdbcTableHandle handle, JdbcColumnHandle column)
    {
        getColumnsCache.remove(handle);
        super.dropColumn(identity, handle, column);
    }