Declarative schema: Incorrect Foreign Key Diff

Question

We created a new table using M2's declarative scheme like this:

<schema xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="urn:magento:framework:Setup/Declaration/Schema/etc/schema.xsd">
    <table name="company_quote_item_original_sku" engine="innodb" resource="default" comment="">
        <column xsi:type="int" name="entity_id" padding="10" unsigned="true" nullable="false" identity="true" comment=""/>
        <column xsi:type="int" name="quote_item_id" padding="10" unsigned="true" nullable="false" comment=""/>
        <column xsi:type="varchar" name="original_sku" nullable="true" length="255" comment=""/>
        <constraint xsi:type="primary" referenceId="PRIMARY">
            <column name="entity_id"/>
        </constraint>
        <constraint xsi:type="foreign" referenceId="FK_QUOTE_ITEM_ID" table="company_quote_item_original_sku"
            column="quote_item_id" referenceTable="quote_item" referenceColumn="item_id"
            onDelete="CASCADE"/>
    </table>
</schema>

This worked great. Then we tried to add another table by updating the schema, like so:

<schema xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="urn:magento:framework:Setup/Declaration/Schema/etc/schema.xsd">
    <table name="company_quote_item_original_sku" engine="innodb" resource="default" comment="">
        <column xsi:type="int" name="entity_id" padding="10" unsigned="true" nullable="false" identity="true" comment=""/>
        <column xsi:type="int" name="quote_item_id" padding="10" unsigned="true" nullable="false" comment=""/>
        <column xsi:type="varchar" name="original_sku" nullable="true" length="255" comment=""/>
        <constraint xsi:type="primary" referenceId="PRIMARY">
            <column name="entity_id"/>
        </constraint>
        <constraint xsi:type="foreign" referenceId="FK_QUOTE_ITEM_ID" table="company_quote_item_original_sku"
            column="quote_item_id" referenceTable="quote_item" referenceColumn="item_id"
            onDelete="CASCADE"/>
    </table>

    <table name="company_order_item_original_sku" engine="innodb" resource="default" comment="">
        <column xsi:type="int" name="entity_id" padding="10" unsigned="true" nullable="false" identity="true" comment=""/>
        <column xsi:type="int" name="order_item_id" padding="10" unsigned="true" nullable="false" comment=""/>
        <column xsi:type="varchar" name="original_sku" nullable="true" length="255" comment=""/>
        <constraint xsi:type="primary" referenceId="PRIMARY">
            <column name="entity_id"/>
        </constraint>
        <constraint xsi:type="foreign" referenceId="FK_ORDER_ITEM_ID" table="company_order_item_original_sku"
            column="order_item_id" referenceTable="sales_order_item" referenceColumn="item_id"
            onDelete="CASCADE"/>
    </table>
</schema>

This triggered the following error:

General error: 1826 Duplicate FOREIGN KEY constraint name 'magento2/COMPANY_QUOTE_ITEM_ORIGINAL_SKU_QUOTE_ITEM_ID_QUOTE_ITEM_ITEM_ID'

ALTER TABLE `company_quote_item_original_sku` MODIFY COLUMN `entity_id` int(10) UNSIGNED NOT NULL  AUTO_IN
CREMENT COMMENT "", MODIFY COLUMN `quote_item_id` int(10) UNSIGNED NOT NULL   COMMENT "", MODIFY COLUMN `original_sku` varchar(255) NULL  COMMENT "", ADD CONSTRAINT `COMPANY_QUOTE_ITEM_ORIGINAL_SKU_QUOTE_ITEM_ID_QUOTE_ITEM_ITEM_ID` FOREIGN KEY (`quote_item_id`) REFER
ENCES `quote_item` (`item_id`)  ON DELETE CASCADE, COMMENT=''

It looks like Magento is incorrectly diffing my existing table and the new schema-generated table. It should do a REMOVE before it does the ADD on the constraint, but it doesn't.

Has anyone seen this before?

Answer 1

From the DevDocs:

Backward compatibility must be maintained. Therefore, declarative schema does not automatically delete database tables, columns or keys that are not defined in a db_schema.xml file.

You must create a db_schema_whitelist.json for your module. In declarative schema a destructive operation is only permitted if allowed in the whitelist.

You can generate the whitelist for your module with the following command:

bin/magento setup:db-declaration:generate-whitelist --module-name[=MODULE-NAME]