Nullable columns and defaults

A plain field can't hold NULL, so ant never has to guess what a zero value means. Use a pointer or sql.Null[T] for any column that can be empty.

Nullable fields

type Profile struct {
	ID      int64
	Bio     *string
	Age     sql.Null[int64]
	Website string
}

profile := &Profile{
	Bio: new("Gopher"), // Go 1.26's new(expr)
	Age: sql.Null[int64]{V: 30, Valid: true},
}

nil is NULL, and a pointer to an empty string is an empty string. They come back from the database just as different as they went in.

Reading NULL into a plain field is an error, not a quiet zero.

Querying for NULL

ant.Eqfunc Eq[V comparable](field *V, v V) CondEq matches rows where field equals v. with nil renders IS NULL, and a pointer value compares what it points to.

noBio, err := db.Users.Where(ant.Eq(&U.Bio, nil)).All(ctx)
same, err := db.Users.Where(ant.IsNull(&U.Bio)).All(ctx)
hasBio, err := db.Users.Where(ant.IsNotNull(&U.Bio)).All(ctx)
gophers, err := db.Users.Where(ant.Eq(&U.Bio, new("Gopher"))).All(ctx)

Setting works the same way, with nil writing NULL.

_, err := db.Users.Where(ant.Eq(&U.ID, id)).Update(ctx, ant.Set(&U.Bio, nil))

Database defaults

ant:"default" says a zero value in this field should be left to the column's default. After the insert, the value the database chose is copied back.

type Account struct {
	ID     int64
	Status string `ant:"default"` // the column has DEFAULT 'new'
}

account := &Account{}

err := db.Accounts.Insert(ctx, account)

fmt.Println(account.Status) // "new"

Migrations need to know the default. ant:"default=0" is short for b.Column(...).Default("0")func (b *ModelBuilder[E]) Column[V any](field *V) *ColumnBuilderColumn configures how a column is declared in migrations., and either one sets the column's DEFAULT too.

func (Post) Configure(b *ant.ModelBuilder[Post]) {
	b.Column(&P.Title).Default("'Untitled'")
}

A default makes zero mean "not set"

This is the one place ant does what it otherwise refuses to: treat zero as "not set". So only put a default on a field whose zero means nothing. With Floor float64 and a default of -100.00, a real 0.00 silently becomes -100.00. Without a default, zero is written as zero.

See it tested: tests/features/model_definition/nullable_test.go