gorm-composite-primary-key

To define a composite primary key in GORM, mark every struct field participating in the unique key with the `primaryKey` tag. This ensures schema migrations and database constraints correctly reflect the combined multi-column uniqueness.

Autoincrement can cause unintended value generation for integer fields within a composite primary key. You must explicitly disable autoincrement for integer key components to preserve correct multi-column uniqueness behavior in GORM migrations.

GORM associations and join tables automatically include all composite primary key columns for many-to-many relations. This ensures that preloads, joins, and foreign keys remain accurate when querying records by multiple key fields.

You need multi-column uniqueness in a GORM database schema when a single column cannot uniquely identify a record, such as localized product catalogs where (product_id, language_code) must uniquely identify a translation record.

Yes, GORM supports querying records by multiple primary key fields when using composite primary keys. Marking each key field as primary ensures that queries reliably retrieve records using the combined unique identifiers.