```ruby
class CreateActiveStorageVariantRecords < ActiveRecord::Migration[6.0]
  def change
    unless table_exists?(:active_storage_variant_records)
      # Use Active Record's configured type for primary key
      create_table :active_storage_variant_records, id: primary_key_type do |t|
        t.belongs_to :blob, null: false, index: false, type: blobs_primary_key_type
        t.string :variation_digest, null: false

        t.index %i[ blob_id variation_digest ], name: "index_active_storage_variant_records_uniqueness", unique: true
        t.foreign_key :active_storage_blobs, column: :blob_id
      end
    end
  end

  private
    def primary_key_type
      config = Rails.configuration.generators
      config.options[config.orm][:primary_key_type] || :primary_key
    end

    def blobs_primary_key_type
      pkey_name = connection.primary_key(:active_storage_blobs)
      pkey_column = connection.columns(:active_storage_blobs).find { |c| c.name == pkey_name }
      pkey_column.bigint? ? :bigint : pkey_column.type
    end
end
```

Use `if_not_exists` instead of `table_exists?`
user
```ruby
class CreateActiveStorageVariantRecords < ActiveRecord::Migration[6.0]
  def change
    # Use Active Record's configured type for primary key
    create_table :active_storage_variant_records, id: primary_key_type, if_not_exists: true do |t|
      t.belongs_to :blob, null: false, index: false, type: blobs_primary_key_type
      t.string :variation_digest, null: false

      t.index %i[ blob_id variation_digest ], name: "index_active_storage_variant_records_uniqueness", unique: true
      t.foreign_key :active_storage_blobs, column: :blob_id
    end
  end

  private
    def primary_key_type
      config = Rails.configuration.generators
      config.options[config.orm][:primary_key_type] || :primary_key
    end

    def blobs_primary_key_type
      pkey_name = connection.primary_key(:active_storage_blobs)
      pkey_column = connection.columns(:active_storage_blobs).find { |c| c.name == pkey_name }
      pkey_column.bigint? ? :bigint : pkey_column.type
    end
end
```
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