Modeling

A Quark model is a plain Go struct. There's no base type to embed and no code generation step: a field becomes a column when it has a db tag, and a field becomes a relation when it has a rel tag. Everything on this page builds on one example struct:

type Product struct {
    ID        int64      `db:"id" pk:"true"`
    SKU       string     `db:"sku" quark:"unique,not_null" validate:"required"`
    Name      string     `db:"name" quark:"not_null"`
    Price     float64    `db:"price" default:"0.00" quark:"not_null"`
    Stock     int        `db:"stock" default:"0"`
    CreatedAt time.Time  `db:"created_at"`
    UpdatedAt time.Time  `db:"updated_at"`
    DeletedAt *time.Time `db:"deleted_at"`
}

Table names

Quark pluralizes and snake-cases the struct name:

Struct	Default table
User	users
Category	categories
APIKey	api_keys
Address	addresses

When the table already exists under another name, implement TableName():

func (Product) TableName() string {
    return "catalog_products"
}

Quark parses and caches a struct's metadata the first time it sees the type, so repeated queries don't re-reflect over the same shape.

The tags you'll use most

These five cover almost everything:

Tag	Does
db:"column"	Maps the field to a column. No db tag → the field is ignored entirely.
pk:"true"	Marks the primary key (or a member of a composite key).
quark:"not_null"	Emits NOT NULL in the schema.
quark:"unique"	Emits UNIQUE. Combine them: quark:"unique,not_null".
validate:"rule"	Runs a validator/v10 rule before writes.

That's enough to model most tables. The rest of this page covers the situations that need more: composite keys, soft deletes, optimistic locking, rich column types, and timezones.

Less common tags (sizing, defaults, renames, optimistic locking)

Tag	Read by	Purpose
db:"column,size=512"	Migrate, Sync	Sets VARCHAR/CHAR length (NVARCHAR/VARCHAR2 per dialect).
db:"column,precision=18,scale=4"	Migrate, Sync, mappers	Forwards precision/scale to DECIMAL emitters and TypeMapper.
db:"-"	parser	Ignores the field.
default:"value"	Migrate	Emits DEFAULT value verbatim; bool defaults are normalized per dialect (below).
nullable:"false"	Migrate	Also emits NOT NULL.
quark:"version"	Update, Tracked.Save	Optimistic-locking column (see below).
quark:"rename:old_col"	Sync	Renames old_col to the current column on the next sync.

type Profile struct {
    ID    int64           `db:"id" pk:"true"`
    Bio   string          `db:"bio,size=512"`
    Price decimal.Decimal `db:"price,precision=18,scale=4"`
}

Unknown db options are ignored, so older tags keep working as new options are added.

Primary keys

Tag the key with pk:"true":

type User struct {
    ID int64 `db:"id" pk:"true"`
}

If no field carries pk:"true", Quark falls back to the field tagged db:"id". An integer single-column key is treated as database-generated when it's zero on insert (so you let the database assign it). String keys are caller-supplied:

type Session struct {
    ID     string `db:"id" pk:"true"`
    UserID int64  `db:"user_id"`
}

Composite keys

Tag more than one field. Migrate emits a table-level PRIMARY KEY (order_id, product_id), and Update / Delete / HardDelete include every key column in the WHERE clause:

item := OrderItem{OrderID: 1001, ProductID: 42, Quantity: 3}
quark.For[OrderItem](ctx, client).Create(&item)

item.Quantity = 5
quark.For[OrderItem](ctx, client).Update(&item)

got, _ := quark.For[OrderItem](ctx, client).
    Where("order_id", "=", 1001).
    Where("product_id", "=", 42).
    First()

fmt.Println(got.Quantity)
// => 5

Find(id) is for single-column keys; query composite keys with explicit Where predicates as above.

Timestamps and soft deletes

A nullable *time.Time field named deleted_at turns on soft deletes: Delete sets the timestamp instead of removing the row, and every read hides it automatically.

type User struct {
    ID        int64      `db:"id" pk:"true"`
    Email     string     `db:"email"`
    DeletedAt *time.Time `db:"deleted_at"`
}

Three modifiers shift the default filter:

Modifier	Filter	Use for
(default)	deleted_at IS NULL	Normal reads.
WithTrashed()	none	Admin/audit listings that include trashed rows.
OnlyTrashed()	deleted_at IS NOT NULL	A trash view, or a restore/purge UI.
Unscoped()	none	Alias of WithTrashed.

u := &User{Email: "x@y.z"}
quark.For[User](ctx, client).Create(u)
quark.For[User](ctx, client).Delete(u) // soft delete

live, _ := quark.For[User](ctx, client).Count()
all, _ := quark.For[User](ctx, client).WithTrashed().Count()
fmt.Println(live, all)
// => 0 1

Restore clears deleted_at for a row you've loaded. Restoring a row that's already live is a harmless 0-row no-op rather than a stray write, so a misuse can't corrupt live data:

trashed, _ := quark.For[User](ctx, client).OnlyTrashed().Find(42)
quark.For[User](ctx, client).Restore(&trashed)

For a permanent delete, use HardDelete (one entity) or DeleteBy / DeleteBatch (by predicate or IDs — both are always hard deletes).

Partial updates and optimistic locking

Update performs a partial update: it skips zero-value fields, so a half-filled struct can't blank out a column with false, 0, or "". To write a zero value on purpose, name it with UpdateMap:

quark.For[User](ctx, client).
    Where("id", "=", 7).
    UpdateMap(map[string]any{"active": false, "score": 0})

To turn a series of free-form mutations into a precise UPDATE instead, load the row with Track() and call Save — see Query Builder and the zero-value note in Getting Started.

Optimistic locking

Add a numeric field tagged quark:"version" to opt into optimistic locking. Every Update, UpdateFields, and Tracked.Save then bumps the version and guards on its loaded value:

type Account struct {
    ID      int64  `db:"id" pk:"true"`
    Owner   string `db:"owner"`
    Balance int64  `db:"balance"`
    Version int64  `db:"version" quark:"version"`
}

a, _ := quark.For[Account](ctx, client).Find(42)
a.Balance = 150
_, err := quark.For[Account](ctx, client).Update(&a)
// emits: UPDATE "accounts" SET "balance" = $1, "version" = "version" + 1
//        WHERE "id" = $2 AND "version" = $3

If another writer advanced the version since your Find, the predicate matches no rows, nothing is written, and you get ErrStaleEntity:

if errors.Is(err, quark.ErrStaleEntity) {
    // reload, replay, retry — or surface the conflict to the user.
}
// => stale conflict: true   (when a concurrent writer won the race)

On success Quark bumps the in-memory version so the next Update sees the new value without a re-read. The version column is automatically NOT NULL, and a model may carry the tag on only one field.

Validation

Quark validates before Create, Upsert, CreateBatch, and UpsertBatch, using validator/v10 tags:

type Member struct {
    ID    int64  `db:"id" pk:"true"`
    Email string `db:"email" validate:"required,email"`
    Role  string `db:"role" validate:"oneof=admin member viewer"`
}

err := quark.For[Member](ctx, client).Create(&Member{Email: "not-an-email", Role: "admin"})
fmt.Println(err != nil)
// => true   (the invalid email is rejected before any SQL runs)

For rules that need code, add a Validate(context.Context) error method — Quark calls it before tag validation:

func (m *Member) Validate(ctx context.Context) error {
    if strings.HasSuffix(m.Email, "@example.invalid") {
        return errors.New("reserved test domain")
    }
    return nil
}

Lifecycle hooks

Add methods to run code around writes:

func (u *User) BeforeCreate(ctx context.Context) error {
    u.CreatedAt = time.Now()
    u.UpdatedAt = u.CreatedAt
    return nil
}

func (u *User) BeforeUpdate(ctx context.Context) error {
    u.UpdatedAt = time.Now()
    return nil
}

The full set is BeforeCreate/AfterCreate, BeforeUpdate/AfterUpdate, BeforeDelete/AfterDelete, plus BeforeFind/AfterFind. Batch writes run the Before* hooks per entity but not After*, and UpdateMap runs none (there's no entity). Lifecycle Hooks has the exact matrix and the post-commit semantics under transactions.

Rich column types

Beyond Go's primitives, Quark ships generic wrappers for the common cases — each implements sql.Scanner and driver.Valuer, so reads and writes use the standard library's fast paths with no extra reflection.

Nullable columns — Nullable[T]

quark.Nullable[T] re-exports database/sql.Null[T] with friendlier constructors. It's the recommended way to model a SQL-NULL-able column:

type Profile struct {
    ID   int64                     `db:"id" pk:"true"`
    Bio  quark.Nullable[string]    `db:"bio"`
    Born quark.Nullable[time.Time] `db:"born"`
}

p := Profile{
    Bio:  quark.SomeOf("hello"),     // set
    Born: quark.NullOf[time.Time](), // SQL NULL
}

Migrate emits T's column type for you. The older *time.Time / sql.NullString idioms still work, but Nullable[T] avoids the pointer's heap allocation and reads more clearly at the call site (p.Bio.Valid vs a nil check).

Typed JSON — JSON[T]

quark.JSON[T] stores any JSON-round-trippable T (struct, map, slice, primitive) and unmarshals it back on read:

type Settings struct {
    Theme  string `json:"theme"`
    Volume int    `json:"volume"`
}

type Pref struct {
    ID       int64                `db:"id" pk:"true"`
    Settings quark.JSON[Settings] `db:"settings"`
}

p := Pref{Settings: quark.JSON[Settings]{V: Settings{Theme: "dark", Volume: 7}}}
quark.For[Pref](ctx, client).Create(&p)

Migrate picks the dialect-native column type: JSONB on PostgreSQL, JSON on MySQL/MariaDB, TEXT on SQLite, NVARCHAR(MAX) on SQL Server, CLOB on Oracle. Wrap it in Nullable[JSON[T]] when you need to tell SQL NULL apart from an empty payload.

Typed arrays — Array[T]

quark.Array[T] is the clearer choice for a list column. It's stored as JSON (same wire format and column type as JSON[[]T]), with list helpers in Go:

p := Post{Tags: quark.Array[string]{V: []string{"go", "orm"}}}
quark.For[Post](ctx, client).Create(&p)

fmt.Println(p.Tags.Len(), p.Tags.Slice())
// => 2 [go orm]

It's deliberately not a PostgreSQL-native TEXT[] wrapper — operators like @> and array_agg won't fire on the JSON column it backs. For native arrays with operators, drop to pgx/pgtype or RawQuery. A nil V serializes to [], not null; wrap in Nullable[Array[T]] to distinguish SQL NULL from "valid but empty".

Binary columns

A plain []byte maps to the native binary type — BYTEA (PostgreSQL), BLOB (MySQL/MariaDB/SQLite/Oracle), VARBINARY(MAX) (SQL Server):

type File struct {
    ID    int64  `db:"id" pk:"true"`
    Bytes []byte `db:"bytes"`
}

Custom types — RegisterTypeMapper

For your own value types (or shopspring/decimal.Decimal, google/uuid.UUID, …), register a mapper at startup. It receives the dialect name and the parsed TypeOptions and returns the SQL column type:

func init() {
    quark.RegisterTypeMapper(reflect.TypeOf(uuid.UUID{}), func(dialect string, _ quark.TypeOptions) string {
        switch dialect {
        case "postgres":
            return "UUID"
        default:
            return "VARCHAR(36)"
        }
    })
}

Pointer types are stripped before lookup, so this also covers *uuid.UUID. The mapper only handles the DDL type; the round-trip still goes through database/sql, so the type must implement sql.Scanner + driver.Valuer (or be natively supported by the driver). The time.Duration mapper ships built in (it emits BIGINT, NUMBER(19) on Oracle).

On SQL Server, store UUIDs as text, not UNIQUEIDENTIFIER

SQL Server stores the first three groups of a GUID little-endian while google/uuid is big-endian, so a UNIQUEIDENTIFIER round-trip hands back a different, silently-wrong UUID. Map uuid.UUID to VARCHAR(36) / NVARCHAR(36) instead (Quark's migrator already does this for string UUID primary keys), or store the driver's own mssql.UniqueIdentifier type if you truly need the native column.

Timezones

By default a time.Time passes through to the driver untouched. Two opt-in knobs let you control the zone: quark.WithDefaultTZ(loc) sets a client-wide fallback, and quark:"tz=Europe/Madrid" overrides a single column.

client, _ := quark.New("postgres", dsn, quark.WithDefaultTZ(time.UTC))

type Event struct {
    ID        int64     `db:"id" pk:"true"`
    CreatedAt time.Time `db:"created_at"`                          // uses the client default (UTC)
    LocalTime time.Time `db:"local_time" quark:"tz=Europe/Madrid"` // column override wins
}

Precedence is column tag → client default → pass-through. The wire contract is always UTC: a zoned column is converted to UTC on the way to the database and back to the configured location when scanned, so the tag changes only how the field reads in Go, never what's stored. Invalid IANA names fail fast at RegisterModel / Migrate with ErrInvalidTimezone, so a typo breaks startup rather than a later query.

Relation fields

Relation fields use a rel tag instead of db, so they aren't treated as columns. They're loaded with Preload and can be saved recursively:

type User struct {
    ID      int64    `db:"id" pk:"true"`
    TeamID  int64    `db:"team_id"`
    Profile *Profile `rel:"has_one" join:"user_id"`
    Posts   []Post   `rel:"has_many" join:"user_id"`
    Team    *Team    `rel:"belongs_to" join:"team_id"`
}

See Relations for the full tag matrix and eager loading.

Inspecting metadata

GetModelMeta[T] returns the cached metadata — handy for tooling, diagnostics, and tests:

meta := quark.GetModelMeta[Product]()
fmt.Println(meta.Table, meta.PK.Column, meta.FieldByCol["sku"].Index)
// => products id 1