docs(core): Show a concrete example migration for deduplicateTranslations

Author: brmk

packages/core/src/migration-utils/translation-deduplication.ts

@@ -13,28 +13,62 @@ import { QueryRunner } from 'typeorm';
  * existing database that already contains such duplicates without first removing them.
  *
  * Call this from your migration's `up()` method **before** the unique constraint on the
- * translation table is created.
+ * translation table is created, once per affected table. `vendure migrate generate` will
+ * generate the DDL that creates the constraints; you only need to add the
+ * `deduplicateTranslations` calls ahead of it. On Postgres this looks like (constraint names
+ * are deterministic, so `vendure migrate generate` will produce these exact names):
  *
  * ```ts
  * import { MigrationInterface, QueryRunner } from 'typeorm';
  * import { deduplicateTranslations } from '\@vendure/core';
  *
- * export class AddTranslationUniqueConstraint1234567890 implements MigrationInterface {
+ * export class AddTranslationUniqueConstraints1234567890 implements MigrationInterface {
  *     public async up(queryRunner: QueryRunner): Promise<any> {
- *         // --- Remove any pre-existing duplicate rows ---
+ *         // --- Remove any pre-existing duplicate rows, one call per translation table ---
  *         await deduplicateTranslations(queryRunner, 'product_translation');
+ *         await deduplicateTranslations(queryRunner, 'product_variant_translation');
+ *         await deduplicateTranslations(queryRunner, 'product_option_translation');
+ *         await deduplicateTranslations(queryRunner, 'product_option_group_translation');
+ *         await deduplicateTranslations(queryRunner, 'collection_translation');
+ *         await deduplicateTranslations(queryRunner, 'facet_translation');
+ *         await deduplicateTranslations(queryRunner, 'facet_value_translation');
+ *         await deduplicateTranslations(queryRunner, 'asset_translation');
+ *         await deduplicateTranslations(queryRunner, 'api_key_translation');
+ *         await deduplicateTranslations(queryRunner, 'payment_method_translation');
+ *         await deduplicateTranslations(queryRunner, 'promotion_translation');
+ *         await deduplicateTranslations(queryRunner, 'region_translation');
+ *         await deduplicateTranslations(queryRunner, 'shipping_method_translation');
  *
- *         // --- Auto-generated DDL continues ---
- *         // (Create the unique index/constraint)
- *         // ...
+ *         // --- Auto-generated DDL continues (Postgres) ---
+ *         await queryRunner.query(`ALTER TABLE "product_translation" ADD CONSTRAINT "UQ_dcc35f0d2b8d422634e878b813c" UNIQUE ("languageCode", "baseId")`);
+ *         await queryRunner.query(`ALTER TABLE "product_variant_translation" ADD CONSTRAINT "UQ_33042b9e7ea5dcf5ec09a5a4130" UNIQUE ("languageCode", "baseId")`);
+ *         await queryRunner.query(`ALTER TABLE "product_option_translation" ADD CONSTRAINT "UQ_bd426ff614344b6759d327fe58c" UNIQUE ("languageCode", "baseId")`);
+ *         await queryRunner.query(`ALTER TABLE "product_option_group_translation" ADD CONSTRAINT "UQ_bb3992fff02944c061363d9d015" UNIQUE ("languageCode", "baseId")`);
+ *         await queryRunner.query(`ALTER TABLE "collection_translation" ADD CONSTRAINT "UQ_858c112351f7714960a2dfcff91" UNIQUE ("languageCode", "baseId")`);
+ *         await queryRunner.query(`ALTER TABLE "facet_translation" ADD CONSTRAINT "UQ_c9174d39ac643e5f14b73ad6cb5" UNIQUE ("languageCode", "baseId")`);
+ *         await queryRunner.query(`ALTER TABLE "facet_value_translation" ADD CONSTRAINT "UQ_084f223aa69bcd7683e727e3130" UNIQUE ("languageCode", "baseId")`);
+ *         await queryRunner.query(`ALTER TABLE "asset_translation" ADD CONSTRAINT "UQ_0dad4e3837a685fea5062da3d96" UNIQUE ("languageCode", "baseId")`);
+ *         await queryRunner.query(`ALTER TABLE "api_key_translation" ADD CONSTRAINT "UQ_0a5a4e1c3fb9547a20f34ef2240" UNIQUE ("languageCode", "baseId")`);
+ *         await queryRunner.query(`ALTER TABLE "payment_method_translation" ADD CONSTRAINT "UQ_5ee20e71a427f7d86e921083777" UNIQUE ("languageCode", "baseId")`);
+ *         await queryRunner.query(`ALTER TABLE "promotion_translation" ADD CONSTRAINT "UQ_0d74bcbf35d65e5d7c2a7947ae1" UNIQUE ("languageCode", "baseId")`);
+ *         await queryRunner.query(`ALTER TABLE "region_translation" ADD CONSTRAINT "UQ_fc1a4a3618bcd16cc50dd50dfeb" UNIQUE ("languageCode", "baseId")`);
+ *         await queryRunner.query(`ALTER TABLE "shipping_method_translation" ADD CONSTRAINT "UQ_6f2a231486b87fd9d337bf9d60b" UNIQUE ("languageCode", "baseId")`);
  *     }
  *
  *     public async down(queryRunner: QueryRunner): Promise<any> {
- *         // Auto-generated reverse DDL
+ *         // Auto-generated reverse DDL — drops the constraints added above.
+ *         // ...
  *     }
  * }
  * ```
  *
+ * On MySQL/MariaDB, unique constraints are implemented as unique indexes, so the generated DDL
+ * instead looks like `` CREATE UNIQUE INDEX `UQ_dcc35f0d2b8d422634e878b813c` ON `product_translation`
+ * (`languageCode`, `baseId`) `` (same deterministic names as above). On SQLite, adding a unique
+ * constraint requires TypeORM to recreate the whole table, so the generated migration will
+ * contain a much longer sequence of statements for each table — call `deduplicateTranslations`
+ * before that generated block in the same way.
+ *
  * @docsCategory migration
  */
 export async function deduplicateTranslations(