-- { echoOn }

SELECT value FROM (SELECT tupleElement(value, 'a') AS value FROM test_table);
0
EXPLAIN QUERY TREE SELECT value FROM (
    SELECT tupleElement(value, 'a') AS value FROM test_table
);
QUERY id: 0
  PROJECTION COLUMNS
    value UInt64
  PROJECTION
    LIST id: 1, nodes: 1
      COLUMN id: 2, column_name: value, result_type: UInt64, source_id: 3
  JOIN TREE
    QUERY id: 3, alias: __table1, is_subquery: 1
      PROJECTION COLUMNS
        value UInt64
      PROJECTION
        LIST id: 4, nodes: 1
          FUNCTION id: 5, function_name: tupleElement, function_type: ordinary, result_type: UInt64
            ARGUMENTS
              LIST id: 6, nodes: 2
                COLUMN id: 7, column_name: value, result_type: Tuple(a UInt64), source_id: 8
                CONSTANT id: 9, constant_value: \'a\', constant_value_type: String
      JOIN TREE
        TABLE id: 8, alias: __table2, table_name: default.test_table
SELECT '--';
--
EXPLAIN QUERY TREE SELECT value FROM (
    SELECT tupleElement(value, 'a') AS value FROM test_table
) SETTINGS optimize_functions_to_subcolumns = 1;
QUERY id: 0
  PROJECTION COLUMNS
    value UInt64
  PROJECTION
    LIST id: 1, nodes: 1
      COLUMN id: 2, column_name: value, result_type: UInt64, source_id: 3
  JOIN TREE
    QUERY id: 3, alias: __table1, is_subquery: 1
      PROJECTION COLUMNS
        value UInt64
      PROJECTION
        LIST id: 4, nodes: 1
          COLUMN id: 5, column_name: value.a, result_type: UInt64, source_id: 6
      JOIN TREE
        TABLE id: 6, alias: __table2, table_name: default.test_table
  SETTINGS optimize_functions_to_subcolumns=1
SELECT '--';
--
EXPLAIN QUERY TREE SELECT value FROM (
    SELECT tupleElement(value, 'a') AS value FROM test_table SETTINGS optimize_functions_to_subcolumns = 0
) SETTINGS optimize_functions_to_subcolumns = 1;
QUERY id: 0
  PROJECTION COLUMNS
    value UInt64
  PROJECTION
    LIST id: 1, nodes: 1
      COLUMN id: 2, column_name: value, result_type: UInt64, source_id: 3
  JOIN TREE
    QUERY id: 3, alias: __table1, is_subquery: 1
      PROJECTION COLUMNS
        value UInt64
      PROJECTION
        LIST id: 4, nodes: 1
          FUNCTION id: 5, function_name: tupleElement, function_type: ordinary, result_type: UInt64
            ARGUMENTS
              LIST id: 6, nodes: 2
                COLUMN id: 7, column_name: value, result_type: Tuple(a UInt64), source_id: 8
                CONSTANT id: 9, constant_value: \'a\', constant_value_type: String
      JOIN TREE
        TABLE id: 8, alias: __table2, table_name: default.test_table
      SETTINGS optimize_functions_to_subcolumns=0
  SETTINGS optimize_functions_to_subcolumns=1
SELECT '--';
--
EXPLAIN QUERY TREE SELECT value FROM (
    SELECT tupleElement(value, 'a') AS value FROM test_table
) SETTINGS optimize_functions_to_subcolumns = 0;
QUERY id: 0
  PROJECTION COLUMNS
    value UInt64
  PROJECTION
    LIST id: 1, nodes: 1
      COLUMN id: 2, column_name: value, result_type: UInt64, source_id: 3
  JOIN TREE
    QUERY id: 3, alias: __table1, is_subquery: 1
      PROJECTION COLUMNS
        value UInt64
      PROJECTION
        LIST id: 4, nodes: 1
          FUNCTION id: 5, function_name: tupleElement, function_type: ordinary, result_type: UInt64
            ARGUMENTS
              LIST id: 6, nodes: 2
                COLUMN id: 7, column_name: value, result_type: Tuple(a UInt64), source_id: 8
                CONSTANT id: 9, constant_value: \'a\', constant_value_type: String
      JOIN TREE
        TABLE id: 8, alias: __table2, table_name: default.test_table
  SETTINGS optimize_functions_to_subcolumns=0
SELECT '--';
--
EXPLAIN QUERY TREE SELECT value FROM (
    SELECT tupleElement(value, 'a') AS value FROM test_table SETTINGS optimize_functions_to_subcolumns = 1
) SETTINGS optimize_functions_to_subcolumns = 0;
QUERY id: 0
  PROJECTION COLUMNS
    value UInt64
  PROJECTION
    LIST id: 1, nodes: 1
      COLUMN id: 2, column_name: value, result_type: UInt64, source_id: 3
  JOIN TREE
    QUERY id: 3, alias: __table1, is_subquery: 1
      PROJECTION COLUMNS
        value UInt64
      PROJECTION
        LIST id: 4, nodes: 1
          COLUMN id: 5, column_name: value.a, result_type: UInt64, source_id: 6
      JOIN TREE
        TABLE id: 6, alias: __table2, table_name: default.test_table
      SETTINGS optimize_functions_to_subcolumns=1
  SETTINGS optimize_functions_to_subcolumns=0