presto-local-file/src/main/java/io/prestosql/plugin/localfile/LocalFileMetadata.java/LocalFileMetadata/listTableColumns
class LocalFileMetadata:    @Override
    public Map<SchemaTableName, List<ColumnMetadata>> listTableColumns(ConnectorSession session, SchemaTablePrefix prefix)
    {
        requireNonNull(prefix, "prefix is null");
        ImmutableMap.Builder<SchemaTableName, List<ColumnMetadata>> columns = ImmutableMap.builder();
        for (SchemaTableName tableName : listTables(session, prefix)) {
            LocalFileTableHandle tableHandle = localFileTables.getTable(tableName);
            if (tableHandle != null) {
                columns.put(tableName, localFileTables.getColumns(tableHandle));
            }
        }
        return columns.build();
    }