Adding comments to columns in codeigniter migrations - mysql

Question

I am writing a lot of migration scripts for the database for my application. I would like to add comments for the columns so that others can easily recognize the column's content. One option is to write normal SQL query and add the comment. But is there a way I can add these comments inside the Migration scipt?
$this->dbforge->add_field(array(
'post_id' => array(
'type' => 'INT',
'constraint' => 11,
'unsigned' => true,
'auto_increment' => true,
'comment' => 'Unique post id'
),
'user_id' => array(
'type' => 'INT',
'constraint' => 11,
'unsigned' => true,
),
'group_id' => array(
'type' => 'INT',
'constraint' => 11,
'unsigned' => true,
),
'source' => array(
'type' => 'VARCHAR',
'constraint' => 20
),
'data' => array(
'type' => 'TEXT',
),
'created' => array(
'type' => 'INT',
'constraint' => 11,
'unsigned' => true,
),
'updated' => array(
'type' => 'INT',
'constraint' => 11,
'unsigned' => true,
),
'status' => array(
'type' => 'INT',
'constraint' => 1,
'unsigned' => true,
)
));
This is the basic code that I have written. May have some syntax error. But I just copy pasted it.
Can anyone please help.

Answer 1

CodeIgniter added this ability with version 3.0. You can add comments using the 'comment' key:
'first_name' => [
'type' => 'VARCHAR',
'constraint' => 45,
'null' => false,
'comment' => 'Put the field comment here',
]

Answer 2

Looking at the CodeIgniter core, specifically system/database/drivers/mysql/mysql_forge.php, it looks like the COMMENT field isn't supported.
For reference, here is the function that parses the fields array out:
function _process_fields($fields)
{
$current_field_count = 0;
$sql = '';
foreach ($fields as $field=>$attributes)
{
// Numeric field names aren't allowed in databases, so if the key is
// numeric, we know it was assigned by PHP and the developer manually
// entered the field information, so we'll simply add it to the list
if (is_numeric($field))
{
$sql .= "\n\t$attributes";
}
else
{
$attributes = array_change_key_case($attributes, CASE_UPPER);
$sql .= "\n\t".$this->db->_protect_identifiers($field);
if (array_key_exists('NAME', $attributes))
{
$sql .= ' '.$this->db->_protect_identifiers($attributes['NAME']).' ';
}
if (array_key_exists('TYPE', $attributes))
{
$sql .= ' '.$attributes['TYPE'];
if (array_key_exists('CONSTRAINT', $attributes))
{
switch ($attributes['TYPE'])
{
case 'decimal':
case 'float':
case 'numeric':
$sql .= '('.implode(',', $attributes['CONSTRAINT']).')';
break;
case 'enum':
case 'set':
$sql .= '("'.implode('","', $attributes['CONSTRAINT']).'")';
break;
default:
$sql .= '('.$attributes['CONSTRAINT'].')';
}
}
}
if (array_key_exists('UNSIGNED', $attributes) && $attributes['UNSIGNED'] === TRUE)
{
$sql .= ' UNSIGNED';
}
if (array_key_exists('DEFAULT', $attributes))
{
$sql .= ' DEFAULT \''.$attributes['DEFAULT'].'\'';
}
if (array_key_exists('NULL', $attributes) && $attributes['NULL'] === TRUE)
{
$sql .= ' NULL';
}
else
{
$sql .= ' NOT NULL';
}
if (array_key_exists('AUTO_INCREMENT', $attributes) && $attributes['AUTO_INCREMENT'] === TRUE)
{
$sql .= ' AUTO_INCREMENT';
}
}
// don't add a comma on the end of the last field
if (++$current_field_count < count($fields))
{
$sql .= ',';
}
}
return $sql;
}

Answer 3

What you can do is the following in the up method just before the closing tag of it:
$this->db->query("ALTER TABLE `" . $this->db->dbprefix . $this->table_name . "` CHANGE `post_id` `post_id` INT(11) UNSIGNED NOT NULL AUTO_INCREMENT COMMENT 'Unique post id'");
Is there any other way to do it without including the column definition in MySQL? No
Note:
Altering a comment will cause a full resconstruction of the table. So you may choose to live without it on very big table.
The Best solution would be to create, extend or copy the mysql or mysqli and reimplementing the _process_fields to handle the comment of the fields. This link can help get you started and this is the advanced.