[bug] Has many does not support nullable IDs

[leahrivkin]

If the ID type on a has-many field is not an int64, looking up the slice of related objects does not work.
Replicated with both *int64 and null.Int.

Code snippet (modified from example/rel-has-many/main.go

package main

import (
	"context"
	"database/sql"
	"fmt"

	"github.com/guregu/null"
	"github.com/uptrace/bun"
	"github.com/uptrace/bun/dialect/sqlitedialect"
	"github.com/uptrace/bun/driver/sqliteshim"
	"github.com/uptrace/bun/extra/bundebug"
)

type Profile struct {
	ID     int64 `bun:",pk,autoincrement"`
	Lang   string
	Active bool
	UserID null.Int
	Person *User `bun:"rel:belongs-to,join:user_id=id"`
}

// User has many profiles.
type User struct {
	ID       int64 `bun:",pk,autoincrement"`
	Name     string
	Profiles []*Profile `bun:"rel:has-many,join:id=user_id"`
}

func main() {
	ctx := context.Background()

	sqldb, err := sql.Open(sqliteshim.ShimName, "file::memory:?cache=shared")
	if err != nil {
		panic(err)
	}

	db := bun.NewDB(sqldb, sqlitedialect.New())
	defer db.Close()

	db.AddQueryHook(bundebug.NewQueryHook(bundebug.WithVerbose(true)))

	if err := createSchema(ctx, db); err != nil {
		panic(err)
	}

	user := new(User)
	err = db.NewSelect().
		Model(user).
		Column("user.*").
		Relation("Profiles", func(q *bun.SelectQuery) *bun.SelectQuery {
			return q.Where("active IS TRUE")
		}).
		OrderExpr("user.id ASC").
		Limit(1).
		Scan(ctx)

	if err != nil {
		fmt.Printf("error getting user: %v\n", err)
		// panic(err)
	} else {
		fmt.Printf("got user: %#v\n", user)
	}

	profile := new(Profile)
	if err := db.NewSelect().
		Model(profile).
		Relation("Person").
		Limit(1).
		Scan(ctx); err != nil {

		fmt.Printf("error getting profile: %v\n", err)
		// panic(err)
	} else {
		fmt.Printf("got profile: %d %s %t %v\n", profile.ID, profile.Lang, profile.Active, profile.Person)
	}
}

func createSchema(ctx context.Context, db *bun.DB) error {
	models := []interface{}{
		(*User)(nil),
		(*Profile)(nil),
	}
	for _, model := range models {
		if _, err := db.NewCreateTable().Model(model).Exec(ctx); err != nil {
			return err
		}
	}

	users := []*User{
		{ID: 1, Name: "user 1"},
		{ID: 2, Name: "user 2"},
	}
	if _, err := db.NewInsert().Model(&users).Exec(ctx); err != nil {
		return err
	}

	profiles := []*Profile{
		{ID: 1, Lang: "en", Active: true, UserID: null.IntFrom(1)},
		{ID: 2, Lang: "ru", Active: true, UserID: null.IntFrom(1)},
		{ID: 3, Lang: "md", Active: false, UserID: null.IntFrom(1)},
	}
	if _, err := db.NewInsert().Model(&profiles).Exec(ctx); err != nil {
		return err
	}

	return nil
}

Output (truncated)

[bun]  17:03:28.936   SELECT                  126µs  SELECT "profile"."id", "profile"."lang", "profile"."active", "profile"."user_id" FROM "profiles" AS "profile" WHERE ("profile"."user_id" IN (1)) AND (active IS TRUE)
error getting user: bun: has-many relation=Profiles does not have base model=User with id=[{{'\x01' %!q(bool=true)}}] (check join conditions)

[bun]  17:03:28.936   SELECT                   26µs  SELECT "profile"."id", "profile"."lang", "profile"."active", "profile"."user_id", "person"."id" AS "person__id", "person"."name" AS "person__name" FROM "profiles" AS "profile" LEFT JOIN "users" AS "person" ON ("person"."id" = "profile"."user_id") LIMIT 1
got profile: 1 en true &{1 user 1 []}

Stacktrace

github.com/alexlast/bunzap.QueryHook.AfterQuery
        pkg/mod/github.com/alexlast/bunzap@v0.1.0/bunzap.go:60
github.com/uptrace/bun.(*DB).afterQueryFromIndex
        src/github.com/uptrace/bun/hook.go:114
github.com/uptrace/bun.(*DB).afterQuery
        src/github.com/uptrace/bun/hook.go:109
github.com/uptrace/bun.(*baseQuery).scan
        src/github.com/uptrace/bun/query_base.go:570
github.com/uptrace/bun.(*SelectQuery).Scan
        src/github.com/uptrace/bun/query_select.go:881
github.com/uptrace/bun.(*relationJoin).selectMany
        src/github.com/uptrace/bun/relation_join.go:53
github.com/uptrace/bun.(*SelectQuery).selectJoins
        src/github.com/uptrace/bun/query_select.go:473
github.com/uptrace/bun.(*SelectQuery).Scan
        src/github.com/uptrace/bun/query_select.go:888
main.main
        src/github.com/uptrace/bun/example/rel-has-many/main.go:68
runtime.main
        /usr/local/go/src/runtime/proc.go:250

[omerfruk]

Hello,

I encountered the same issue and went a step further to identify the root cause. However, this may not necessarily be a problem; it could be a matter of preference. For instance, when establishing a BelongsTo relations, you can set the value as null, but doing the same for a HasMany relations results in an error. This behavior might be intentional. Therefore, I wanted to ask you whether this is considered an error or a matter of preference. I have provided screenshots of the relevant field below.

Thank you.

As seen above, if the value is a pointer(which can be null), it throws an error.

However, as seen here, if the data is not a pointer(cannot be null), you do not receive an error, just like in the documentation.

bun/model_table_has_many.go

Lines 105 to 130 in 838a3bc

	func (m *hasManyModel) parkStruct() error {
	baseValues, ok := m.baseValues[internal.NewMapKey(m.structKey)]
	if !ok {
	return fmt.Errorf(
	"bun: has-many relation=%s does not have base %s with id=%q (check join conditions)",
	m.rel.Field.GoName, m.baseTable, m.structKey)
	}
	for i, v := range baseValues {
	if !m.sliceOfPtr {
	v.Set(reflect.Append(v, m.strct))
	continue
	}
	if i == 0 {
	v.Set(reflect.Append(v, m.strct.Addr()))
	continue
	}
	clone := reflect.New(m.strct.Type()).Elem()
	clone.Set(m.strct)
	v.Set(reflect.Append(v, clone.Addr()))
	}
	return nil
	}

The location where the error is being

If this is indeed a bug, I would be glad to assist you in troubleshooting and resolving the issue.

[leahrivkin]

Thank you @omerfruk ! The main source of confusion was that null.Int works perfectly for belongs-to. Our workaround is for now is to just not use has-many