Doctrine\DBAL\Platforms\MySqlPlatform::getPreAlterTableAlterIndexForeignKeySQL PHP Method

    private function getPreAlterTableAlterIndexForeignKeySQL(TableDiff $diff)
    {
        $sql = array();
        $table = $diff->getName($this)->getQuotedName($this);
        foreach ($diff->changedIndexes as $changedIndex) {
            // Changed primary key
            if ($changedIndex->isPrimary() && $diff->fromTable instanceof Table) {
                foreach ($diff->fromTable->getPrimaryKeyColumns() as $columnName) {
                    $column = $diff->fromTable->getColumn($columnName);
                    // Check if an autoincrement column was dropped from the primary key.
                    if ($column->getAutoincrement() && !in_array($columnName, $changedIndex->getColumns())) {
                        // The autoincrement attribute needs to be removed from the dropped column
                        // before we can drop and recreate the primary key.
                        $column->setAutoincrement(false);
                        $sql[] = 'ALTER TABLE ' . $table . ' MODIFY ' . $this->getColumnDeclarationSQL($column->getQuotedName($this), $column->toArray());
                        // Restore the autoincrement attribute as it might be needed later on
                        // by other parts of the table alteration.
                        $column->setAutoincrement(true);
                    }
                }
            }
        }
        return $sql;
    }