Deletion System Documentation

Overview

The deletion system manages cascading deletes, foreign key constraints, and referential integrity when records are permanently deleted from the database. It uses a child-centric, declarative approach where dependent models declare their own behavior when parent records are deleted.

> GET-is-read-only: soft_delete() and permanent_delete() (like save()) refuse to run on a GET request — a GET must not mutate data. A legitimate GET-action delete link must wrap the call in SystemBase::$allow_get_mutation = true; try { … } finally { SystemBase::$allow_get_mutation = false; }. See Logic Architecture — GET-is-read-only invariant.

Key Concepts

• Child-Centric: Child models declare how they should be handled when their parent is deleted (not the other way around)
• Auto-Detection: Foreign keys are automatically detected from column naming patterns (xxx_yyy_entity_id)
• Incremental Registration: Deletion rules are registered per-model without affecting other models' rules
• Default CASCADE: If no behavior is specified, dependent records are deleted automatically
• Separation of Concerns: Core and plugin deletion rules are managed independently

How It Works

1. Foreign Key Auto-Detection

The system automatically detects foreign keys based on column naming:

Pattern: {prefix}_{source_prefix}_{entity}_id

Examples:
- ord_usr_user_id → references usr_users table
- odi_pro_product_id → references pro_products table
- evt_loc_location_id → references loc_locations table

The system:

1. Extracts the entity name (e.g., "user", "product", "location")
2. Pluralizes it (user → users, category → categories)
3. Adds the source prefix to build the table name (usr_users, pro_products, loc_locations)

2. Deletion Actions

Five actions are available:

3. Default Behavior

If no $foreign_key_actions is specified:

• Default action: cascade (dependent records are deleted)
• This is safe for most relationships and eliminates configuration for common cases

Using $foreign_key_actions in Models

Basic Examples

Most Common: Set to Deleted User

class Order extends SystemBase {
    public static $tablename = 'ord_orders';

    protected static $foreign_key_actions = [
        'ord_usr_user_id' => ['action' => 'set_value', 'value' => User::USER_DELETED]
    ];
}

Prevent Deletion

class OrderItem extends SystemBase {
    public static $tablename = 'odi_order_items';

    protected static $foreign_key_actions = [
        'odi_pro_product_id' => [
            'action' => 'prevent',
            'message' => 'Cannot delete product - order items exist'
        ]
    ];
}

Set to NULL

class Event extends SystemBase {
    public static $tablename = 'evt_events';

    protected static $foreign_key_actions = [
        'evt_loc_location_id' => ['action' => 'null']
    ];
}

No Configuration Needed (Cascade)

class UserActivityLog extends SystemBase {
    public static $tablename = 'ual_user_activity_logs';

    // No $foreign_key_actions needed!
    // ual_usr_user_id will automatically cascade delete
}

Multiple Foreign Keys

Handle different foreign keys with different actions:

class Message extends SystemBase {
    public static $tablename = 'msg_messages';

    protected static $foreign_key_actions = [
        'msg_usr_sender_id' => ['action' => 'set_value', 'value' => User::USER_DELETED],
        'msg_usr_recipient_id' => ['action' => 'set_value', 'value' => User::USER_DELETED],
        'msg_thread_id' => ['action' => 'cascade']  // Optional: explicit cascade
    ];
}

Deletion Rule Registration Lifecycle

Core Models

Core model deletion rules are registered by update_database.php:

// In /utils/update_database.php (Step 3.5)
DeletionRule::registerModelsFromDiscovery([
    'include_plugins' => false,  // Core only
    'verbose' => $verbose
]);

When: Every time update_database.php runs

Plugin Models

Plugin deletion rules are registered/removed through PluginManager lifecycle operations:

1. Plugin Activate: PluginManager::activate() (onActivate()) registers rules for that plugin
2. Plugin Deactivate: PluginManager::deactivate() (onDeactivate()) removes rules for that plugin
3. Plugin Uninstall: PluginManager::uninstall() removes rules for that plugin

Manual Registration

To manually register deletion rules for all active plugins:

require_once(PathHelper::getIncludePath('includes/PluginHelper.php'));
PluginHelper::registerAllActiveDeletionRules();

How Deletion Works

Dry Run Preview

Before deleting, check what will be affected:

$user = new User($user_id, TRUE);
$dry_run = $user->permanent_delete_dry_run();

// Returns:
// [
//     'primary' => ['table' => 'usr_users', 'key_column' => 'usr_user_id', 'key' => 123],
//     'dependencies' => [
//         ['table' => 'ord_orders', 'column' => 'ord_usr_user_id', 'count' => 5,
//          'action' => 'set_value', 'action_value' => 3],
//         ['table' => 'ual_user_activity_logs', 'column' => 'ual_usr_user_id',
//          'count' => 150, 'action' => 'cascade']
//     ],
//     'total_affected' => 156,
//     'can_delete' => true,
//     'blocking_reasons' => []
// ]

Permanent Delete

The system handles dependencies automatically:

$user = new User($user_id, TRUE);
$user->authenticate_write(['current_user_id' => $session_id, 'current_user_permission' => 10]);
$user->permanent_delete();

// Automatically:
// 1. Updates orders to set usr_user_id = 3 (DELETED_USER)
// 2. Cascades delete of user activity logs
// 3. Handles all other dependencies per their rules
// 4. Deletes the user record
// 5. Commits transaction

Custom Deletion Logic

Models can override permanent_delete() for custom behavior:

class User extends SystemBase {
    public function permanent_delete($debug=false) {
        // Custom pre-deletion work
        $this->remove_from_mailing_lists();
        $this->remove_group_memberships();

        // Call parent to handle dependencies and delete
        parent::permanent_delete($debug);

        return true;
    }
}

Important: Custom methods should call parent::permanent_delete() to use the deletion system.

Database Structure

Deletion rules are stored in the del_deletion_rules table:

CREATE TABLE del_deletion_rules (
    del_id BIGSERIAL PRIMARY KEY,
    del_source_table VARCHAR(255),      -- Parent table (e.g., 'usr_users')
    del_target_table VARCHAR(255),      -- Child table (e.g., 'ord_orders')
    del_target_column VARCHAR(255),     -- Foreign key column (e.g., 'ord_usr_user_id')
    del_action VARCHAR(50),             -- 'cascade', 'set_value', 'null', 'prevent'
    del_action_value VARCHAR(255),      -- Value for 'set_value' action
    del_message TEXT,                   -- Message for 'prevent' action
    del_plugin VARCHAR(255)             -- Plugin name (NULL for core)
);

Troubleshooting

Check Current Rules

-- See all deletion rules
SELECT * FROM del_deletion_rules ORDER BY del_source_table, del_target_table;

-- Rules for a specific table
SELECT * FROM del_deletion_rules WHERE del_source_table = 'usr_users';

-- Plugin rules only
SELECT * FROM del_deletion_rules WHERE del_plugin IS NOT NULL;

-- Count by action type
SELECT del_action, COUNT(*) FROM del_deletion_rules GROUP BY del_action;

Common Issues

Problem: Deletion rules not registered for plugin Solution:

• Check if plugin is active (plg_active = 1)
• Deactivate and re-activate the plugin — activation re-registers deletion rules
• Or from CLI: PluginHelper::registerAllActiveDeletionRules()

• Check $foreign_key_actions in your model class
• Verify column name matches pattern: {prefix}_{source_prefix}_{entity}_id
• Re-register rules by syncing or reactivating plugin

• Check for 'prevent' actions in del_deletion_rules for that source table
• Use permanent_delete_dry_run() to see what's blocking deletion
• Either remove dependencies or change action from 'prevent' to another action

• Already fixed in SystemBase - it checks inTransaction() before starting new transaction
• If you see this, you may have custom code starting transactions

Debug Tools

See what will be deleted:

$obj = new SomeModel($id, TRUE);
$preview = $obj->permanent_delete_dry_run();
print_r($preview);

Test in debug mode (no actual deletion):

$obj->permanent_delete($debug = true);  // Prints SQL without executing

Technical Implementation

Key Classes

DeletionRule (/data/deletion_rule_class.php)

• registerModelsFromDiscovery($options) - Discover and register model rules
• registerModelRules($model_class) - Register one model's rules incrementally
• getSourceTableFromColumn($column) - Parse foreign key column to find source table

• permanent_delete_dry_run() - Preview deletion impact
• permanent_delete($debug) - Execute deletion with dependency handling

• registerAllActiveDeletionRules() - Register rules for all active plugins
• removePluginDeletionRules() - Remove rules for one plugin

Algorithm

When permanent_delete() is called:

1. Start transaction (if not already in one)
2. Query deletion rules from del_deletion_rules for this source table
3. For each dependent table: - Count how many dependent records exist - If count > 0, apply the action: - cascade: DELETE dependent records - set_value: UPDATE dependent records to set value - null: UPDATE dependent records to NULL - prevent: THROW error and rollback
4. Delete the primary record
5. Commit transaction

Designing a Deletion Strategy for New Models

When creating a new model with parent-child relationships, plan for both soft delete and permanent delete:

1. Permanent Delete ($foreign_key_actions)

Declare on the child model what happens when its parent is permanently deleted:

// Child model — alias belongs to a domain
class InboundEmailAlias extends SystemBase {
    protected static $foreign_key_actions = [
        'iea_ied_inbound_email_domain_id' => ['action' => 'cascade'],
    ];
}

// Grandchild model — log references an alias, preserve for auditing
class InboundEmailLog extends SystemBase {
    protected static $foreign_key_actions = [
        'iel_iea_inbound_email_alias_id' => ['action' => 'null'],
    ];
}

2. Soft Delete Cascading

$foreign_key_actions only applies to permanent_delete(). Soft-delete cascading must be implemented manually in your deletion logic. When a parent is soft-deleted, children often need to be soft-deleted too:

// In admin logic — soft-delete domain cascades to aliases
$domain->soft_delete();

$aliases = new MultiInboundEmailAlias([
    'domain_id' => $domain->key,
    'deleted' => false,
]);
$aliases->load();
foreach ($aliases as $alias) {
    $alias->soft_delete();
}

3. Undelete with Cascade Awareness

When restoring a soft-deleted parent, only restore children that were deleted at the same time or after the parent. Children independently deleted before the parent should remain deleted:

$domain_delete_time = $domain->get('efd_delete_time');
$domain->undelete();

// Restore only aliases deleted when/after the domain was deleted
$sql = "UPDATE efa_email_forwarding_aliases
        SET efa_delete_time = NULL
        WHERE efa_efd_email_forwarding_domain_id = ?
        AND efa_delete_time >= ?";
$q = $dblink->prepare($sql);
$q->execute([$domain->key, $domain_delete_time]);

Checklist for New Models

• [ ] Define $foreign_key_actions on child models for permanent delete behavior
• [ ] Implement soft-delete cascade in the admin/logic layer if parent-child relationship exists
• [ ] Implement undelete logic that respects independently-deleted children
• [ ] Consider whether logs/audit records should use 'action' => 'null' to preserve history
• [ ] Require appropriate permission level for permanent delete (typically 10)

Best Practices

1. Use constants for sentinel values: User::USER_DELETED instead of hardcoded 3
2. Add messages for prevent actions: Help users understand why deletion failed
3. Test deletion impact: Use permanent_delete_dry_run() before actual deletion
4. Prefer CASCADE for logs and temporary data: Default behavior is usually correct
5. Use PREVENT sparingly: Only for truly critical references that can't be orphaned
6. Document custom permanent_delete(): Explain any special pre/post-deletion logic

Migration from Old System

The old system used $permanent_delete_actions in parent models:

// OLD (deprecated)
class User extends SystemBase {
    public static $permanent_delete_actions = [
        'ord_usr_user_id' => User::USER_DELETED  // Parent declares child behavior
    ];
}

New system uses $foreign_key_actions in child models:

// NEW (current)
class Order extends SystemBase {
    protected static $foreign_key_actions = [
        'ord_usr_user_id' => ['action' => 'set_value', 'value' => User::USER_DELETED]
    ];
}

Why the change?

• Child models know their own requirements better than parents
• Prevents tight coupling between unrelated models
• Allows plugins to define behavior without modifying core
• More explicit action specification
• Supports prevent/null actions that didn't exist before