feat(query): add Query, MustQuery, and UpdateOne helpers

Adds scan-into-dest query helpers and update-one-row semantics with
Context variants, tests, and documentation updates.

Co-authored-by: Cursor <cursoragent@cursor.com>

CHANGELOG.md

@@ -13,6 +13,7 @@
 ### Added
 
 - `StringKSUID.Equal` / `IsZero`, `BinaryKSUID.Equal` / `IsZero`, and nil sentinel vars for [ApplyInterfacePtr].
+- `Query`, `MustQuery`, and `UpdateOne` helpers (+ Context variants).
 - Context-aware variants for all query and mutation helpers.
 - `Delete`, `DeleteAffected`, `WithTx`, `ContainsCol`, and `CurrentDialect()`.
 - Package documentation (`doc.go`), expanded README, and subpackage docs for `dbxm` / `dbxp`.

README.md

@@ -42,8 +42,8 @@ For Postgres, use `dbx.DialectPostgres` and blank-import `dbxp` instead of `dbxm
 
 | Area | Functions |
 |------|-----------|
-| Query | `Fetch`, `MustFetch`, `FetchOne`, `MustFetchOne` (+ `*Context` variants) |
-| Mutations | `Insert`, `InsertReturning`, `Update`, `UpdateAffected`, `UpdateReturning`, `Delete`, `DeleteAffected` (+ `*Context` variants) |
+| Query | `Fetch`, `MustFetch`, `FetchOne`, `MustFetchOne`, `Query`, `MustQuery` (+ `*Context` variants) |
+| Mutations | `Insert`, `InsertReturning`, `Update`, `UpdateAffected`, `UpdateOne`, `UpdateReturning`, `Delete`, `DeleteAffected` (+ `*Context` variants) |
 | Transactions | `WithTx` |
 | Columns | `NormalCols`, `ContainsCol`, `ExprValues`, `ExprStringers` |
 | Partial update | `ApplyPtr`, `ApplyComplexPtr`, `ApplyInterfacePtr`, `ApplyVal` |

doc.go

@@ -8,8 +8,9 @@
 //
 // # Query and mutation helpers
 //
-// [Fetch], [FetchOne], [Insert], [Update], [Delete], and their Must* and Context
-// variants wrap Jet [Statement] execution with consistent error semantics.
+// [Fetch], [FetchOne], [Query], [Insert], [Update], [Delete], and their Must*
+// and Context variants wrap Jet [Statement] execution with consistent error
+// semantics. [UpdateOne] requires at least one row affected.
 // [WithTx] runs a function inside a SQL transaction.
 //
 // # Jet column utilities

exec.go

@@ -74,6 +74,24 @@ func UpdateAffectedContext(ctx context.Context, sqlo Executable, stmt Statement)
 	return rowsAffected, nil
 }
 
+// UpdateOne executes an update statement and returns notFoundErr if zero rows
+// were affected.
+func UpdateOne(sqlo Executable, stmt Statement, notFoundErr error) error {
+	return UpdateOneContext(context.Background(), sqlo, stmt, notFoundErr)
+}
+
+// UpdateOneContext is the context-aware variant of [UpdateOne].
+func UpdateOneContext(ctx context.Context, sqlo Executable, stmt Statement, notFoundErr error) error {
+	n, err := UpdateAffectedContext(ctx, sqlo, stmt)
+	if err != nil {
+		return err
+	}
+	if n == 0 {
+		return notFoundErr
+	}
+	return nil
+}
+
 // UpdateReturning executes an update statement that returns the updated row.
 // The statement MUST be a Jet UpdateStatement with a RETURNING clause. Returns
 // the updated row object T or an error if the update fails or no rows are returned.

exec_test.go

@@ -60,6 +60,29 @@ func TestUpdateAffected_ReturnsCount(t *testing.T) {
 	assert.Equal(t, int64(3), n)
 }
 
+func TestUpdateOne_NotFound(t *testing.T) {
+	errNotFound := errors.New("not found")
+	stmt := mockStatement{
+		execContextFn: func(_ context.Context) (sql.Result, error) {
+			return mockResult{rowsAffected: 0}, nil
+		},
+	}
+
+	err := UpdateOne(mockExecutable{}, stmt, errNotFound)
+	assert.ErrorIs(t, err, errNotFound)
+}
+
+func TestUpdateOne_Success(t *testing.T) {
+	stmt := mockStatement{
+		execContextFn: func(_ context.Context) (sql.Result, error) {
+			return mockResult{rowsAffected: 1}, nil
+		},
+	}
+
+	err := UpdateOne(mockExecutable{}, stmt, errors.New("not found"))
+	require.NoError(t, err)
+}
+
 func TestDelete_Succeeds(t *testing.T) {
 	called := false
 	stmt := mockStatement{

query.go

@@ -70,3 +70,31 @@ func MustFetchOneContext[T any](ctx context.Context, sqlo Queryable, stmt Statem
 	}
 	return result[0], nil
 }
+
+// Query executes a Jet statement and scans the result into dest.
+func Query(sqlo Queryable, stmt Statement, dest any) error {
+	return QueryContext(context.Background(), sqlo, stmt, dest)
+}
+
+// QueryContext is the context-aware variant of [Query].
+func QueryContext(ctx context.Context, sqlo Queryable, stmt Statement, dest any) error {
+	return stmt.QueryContext(ctx, sqlo, dest)
+}
+
+// MustQuery executes a Jet statement and scans the result into dest. If the
+// query returns no rows, notFoundErr is returned instead of [ErrNoRows].
+func MustQuery(sqlo Queryable, stmt Statement, dest any, notFoundErr error) error {
+	return MustQueryContext(context.Background(), sqlo, stmt, dest, notFoundErr)
+}
+
+// MustQueryContext is the context-aware variant of [MustQuery].
+func MustQueryContext(ctx context.Context, sqlo Queryable, stmt Statement, dest any, notFoundErr error) error {
+	err := stmt.QueryContext(ctx, sqlo, dest)
+	if err != nil {
+		if errors.Is(err, ErrNoRows) {
+			return notFoundErr
+		}
+		return err
+	}
+	return nil
+}

query_test.go

@@ -91,3 +91,45 @@ func TestMustFetchOne_NotFound(t *testing.T) {
 	assert.Nil(t, result)
 	assert.ErrorIs(t, err, errNotFound)
 }
+
+func TestQuery_ScansDest(t *testing.T) {
+	stmt := mockStatement{
+		queryContextFn: func(_ context.Context, dest any) error {
+			ptr := dest.(*row)
+			ptr.ID = 5
+			return nil
+		},
+	}
+
+	var result row
+	err := Query(mockQueryable{}, stmt, &result)
+	require.NoError(t, err)
+	assert.Equal(t, 5, result.ID)
+}
+
+func TestMustQuery_NotFound(t *testing.T) {
+	errNotFound := errors.New("not found")
+	stmt := mockStatement{
+		queryContextFn: func(_ context.Context, _ any) error {
+			return ErrNoRows
+		},
+	}
+
+	var result row
+	err := MustQuery(mockQueryable{}, stmt, &result, errNotFound)
+	assert.ErrorIs(t, err, errNotFound)
+}
+
+func TestMustQueryContext_PropagatesContext(t *testing.T) {
+	ctx := context.WithValue(context.Background(), testContextKey{}, "ok")
+	var gotCtx context.Context
+	stmt := mockStatement{
+		queryContextFn: func(c context.Context, dest any) error {
+			gotCtx = c
+			return ErrNoRows
+		},
+	}
+
+	_ = MustQueryContext(ctx, mockQueryable{}, stmt, &row{}, errors.New("nf"))
+	assert.Equal(t, ctx, gotCtx)
+}