protected function collectIndexedColumns($indexName, $columns, &$collectedIndexes)
	{
		/**
		 * "If the table has a multiple-column index, any leftmost prefix of the
		 * index can be used by the optimizer to find rows. For example, if you
		 * have a three-column index on (col1, col2, col3), you have indexed search
		 * capabilities on (col1), (col1, col2), and (col1, col2, col3)."
		 * @link http://dev.mysql.com/doc/refman/5.5/en/mysql-indexes.html
		*/
		$indexedColumns = array();
		foreach ($columns as $column) {
			$indexedColumns[] = $column;
			$indexedColumnsHash = $this->getColumnList($indexedColumns);
			if (!array_key_exists($indexedColumnsHash, $collectedIndexes)) {
				$collectedIndexes[$indexedColumnsHash] = array();
			}
			$collectedIndexes[$indexedColumnsHash][] = $indexName;
		}
	}