Osm Admin: Table Diff. Renaming Tables

Yesterday, I continued working on schema migrations:

• implemented table diff algorithm;
• took into consideration table renames.

Read more:

• Table::diff()
• Renaming Tables
  • Renaming Table Class
  • Renaming Database Table

Table::diff()

On a table level, everything depends on properties on the record class, and on indexers that listen to the changes in the given table. So, let's create empty CREATE/ALTER migrations and fill them in according to table properties and listeners. If some property fills in an ALTER migration, it will be executed, otherwise it will not:

// Osm\Admin\Schema\Table
public function diff(Migrators\Schema $migrator,
    \stdClass|Table|null $old): void
{
    if ($old) {
        $migrator->alter_tables[] = $table = Migrators\Table\Alter::new([
            'table_name' => $this->table_name,
        ]);
        $migrator->alter_indexes[] = $index = Migrators\Index\Alter::new([
            'index_name' => $this->table_name,
        ]);
    }
    else {
        $migrator->create_tables[] = $table = Migrators\Table\Create::new([
            'table_name' => $this->table_name,
        ]);
        $migrator->create_indexes[] = $index = Migrators\Index\Create::new([
            'index_name' => $this->table_name,
        ]);
    }

    $migrator->create_notifications[] = $createNotifications =
        Migrators\Notification\Create::new([
            'table_name' => $table->table_name,
        ]);
    $migrator->drop_notifications[] = $dropNotifications =
        Migrators\Notification\Drop::new([
            'table_name' => $table->table_name,
        ]);

    foreach ($this->properties as $property) {
        throw new NotImplemented($this);
    }

    foreach ($this->listeners as $listener) {
        throw new NotImplemented($this);
    }
}

Renaming Tables

Talking about renaming tables, there are kind of renames: renaming a class, and renaming the database table.

Renaming Table Class

Renaming a class is done using the #[Rename] attribute:

// V1
class Item extends Record {
}

// V2  
#[Rename(Item::class)]
class Product extends Record {
}

This change doesn't affect database tables. However, the Schema::diff() needs to catch up:

protected function diff(\stdClass|Schema|null $old): Migrators\Schema
{
    ...
    foreach ($this->tables as $table) {
        if ($table->rename) {
            $name = $table->rename;
            if (!isset($old->tables->$name)) {
                throw new InvalidRename(__(
                    "Previous schema doesn't contain the ':old_name' table referenced in the #[Rename] attribute of the ':new_name' table.",
                    ['old_name' => $table->rename, 'new_name' => $table->name]));
            }
        }
        else {
            $name = $table->name;
        }

        $table->diff($migrator, $old->tables->$name ?? null);
    }
    ...
}

Renaming Database Table

Renaming the underlying database table is done by changing #[Table] attribute:

// V1
class Product extends Record {
}

// V2  
#[Table('my_products')]
class Product extends Record {
}

Notice. If you don't use #[Table] attribute, the database table name may change after renaming/moving the table class, as in this case the database table name is inferred from the class name.

Renaming is "ordered" in the Table::diff():

public function diff(Migrator\Schema $migrator,
                     \stdClass|Table|null $old): void
{
    if ($old) {
        ...
        if ($this->table_name !== $old->table_name) {
            $migrator->rename_tables[] = $table = Migrator\Table\Rename::new([
                'old_table_name' => $old->table_name,
                'table_name' => $this->table_name,
            ]);
            $migrator->rename_indexes[] = $index = Migrator\Index\Rename::new([
                'old_index_name' => $old->table_name,
                'index_name' => $this->table_name,
            ]);
            $migrator->rename_all_notifications[] = Migrator\Notification\RenameAll::new([
                'old_table_name' => $old->table_name,
                'table_name' => $table->table_name,
            ]);
        } 
    }
    ...
}