presto-base-jdbc/src/main/java/io/prestosql/plugin/jdbc/JdbcMetadata.java/JdbcMetadata/getColumnHandles
class JdbcMetadata:    @Override
    public Map<String, ColumnHandle> getColumnHandles(ConnectorSession session, ConnectorTableHandle tableHandle)
    {
        JdbcTableHandle jdbcTableHandle = (JdbcTableHandle) tableHandle;

        ImmutableMap.Builder<String, ColumnHandle> columnHandles = ImmutableMap.builder();
        for (JdbcColumnHandle column : jdbcClient.getColumns(session, jdbcTableHandle)) {
            columnHandles.put(column.getColumnMetadata().getName(), column);
        }
        return columnHandles.build();
    }