Check effect of hook_schema_alter() hook

Question

I want to alter the comment subject field title width.

Core comment module sets it to 64 characters, and I want to change it up to 100 characters.

Now I tried to alter the schema using hook_schema_alter() function. Below is my code snippet, which I tried,

/**
 * Implements hook_schema_alter().
 */
function comment_alter_schema_alter(&$schema) {
    if (isset($schema['comment'])) {
        $schema['comment']['fields']['subject'] = array(
        'type' => 'varchar',
        'length' => 100,
        'not null' => TRUE,
        'default' => '',
        'description' => 'The comment title.',
        );
    }
}

I am confused whether do I have to write some stuff in .install file or not?

Now after installing module how can i check whether the width of subject field is increased or not. If I see the comment table then it is as it is to 64 characters. I could find this in your table structure using PHPMyAdmin.

Answer 1

This hook is not used to edit the database as such. It is used to alter the schema when using the drupal_get_schema

Gets the schema definition of a table, or the whole database schema.

The returned schema will include any modifications made by any module that implements hook_schema_alter().

To do what you want you will have to use the db_change_field and this would go in the .install file.

You can check out the Schema API to get other relavent functions

You have to write db_change_field() in hook_enable() function.

Here is my modified answer:

/**
 * Implements hook_enable().
 */
function comment_alter_enable() {
    db_change_field('comment', 'subject', 'subject', array(
        'type' => 'varchar',
        'length' => 100,
        'not null' => TRUE,
        'default' => '',
        'description' => 'The comment title.',
        )
    );
}