code: public function findUniqueIndexes($table)
      {
          $query = <<<'SQL'
  SELECT
      DIC.INDEX_NAME,
      DIC.COLUMN_NAME
  FROM ALL_INDEXES DI
      INNER JOIN ALL_IND_COLUMNS DIC ON DI.TABLE_NAME = DIC.TABLE_NAME AND DI.INDEX_NAME = DIC.INDEX_NAME
  WHERE
      DI.UNIQUENESS = 'UNIQUE'
      AND DIC.TABLE_OWNER = :schemaName
      AND DIC.TABLE_NAME = :tableName
  ORDER BY DIC.TABLE_NAME, DIC.INDEX_NAME, DIC.COLUMN_POSITION
  SQL;
          $result = [];
          $command = $this->db->createCommand($query, [
              ':tableName' => $table->name,
              ':schemaName' => $table->schemaName,
          ]);
          foreach ($command->queryAll() as $row) {
              $result[$row['INDEX_NAME']][] = $row['COLUMN_NAME'];
          }
  
          return $result;
      }
docs: Returns all unique indexes for the given table.
  Each array element is of the following structure:.
  
  ```php
  [
  'IndexName1' => ['col1' [, ...]],
  'IndexName2' => ['col2' [, ...]],
  ]
  ```
  
  @param TableSchema $table the table metadata
  @return array all unique indexes for the given table.
  @since 2.0.4