Additional scan performance improvements

Move typeStack to ScanContext, so it is shared between rows.Scan calls.
Use string.Builder for string concatenations.
Simplify value assign logic.
Move convert value to the last assign step (needs for type conversions are rare).

tests/postgres/select_test.go

@@ -2521,6 +2521,79 @@ func TestRecursionScanNx1(t *testing.T) {
 	})
 }
 
+type StoreInfo struct {
+	model.Store
+
+	Staffs ManagerInfo
+}
+
+type ManagerInfo struct {
+	model.Staff
+	Store *StoreInfo
+}
+
+func TestRecursionScan1x1(t *testing.T) {
+
+	stmt := SELECT(
+		Store.AllColumns,
+		Staff.AllColumns,
+	).FROM(
+		Store.
+			INNER_JOIN(Staff, Staff.StaffID.EQ(Store.ManagerStaffID)),
+	).ORDER_BY(
+		Store.StoreID,
+	)
+
+	var dest []StoreInfo
+
+	err := stmt.Query(db, &dest)
+	require.NoError(t, err)
+	testutils.AssertJSON(t, dest, `
+[
+	{
+		"StoreID": 1,
+		"ManagerStaffID": 1,
+		"AddressID": 1,
+		"LastUpdate": "2006-02-15T09:57:12Z",
+		"Staffs": {
+			"StaffID": 1,
+			"FirstName": "Mike",
+			"LastName": "Hillyer",
+			"AddressID": 3,
+			"Email": "Mike.Hillyer@sakilastaff.com",
+			"StoreID": 1,
+			"Active": true,
+			"Username": "Mike",
+			"Password": "8cb2237d0679ca88db6464eac60da96345513964",
+			"LastUpdate": "2006-05-16T16:13:11.79328Z",
+			"Picture": "iVBORw0KWgo=",
+			"Store": null
+		}
+	},
+	{
+		"StoreID": 2,
+		"ManagerStaffID": 2,
+		"AddressID": 2,
+		"LastUpdate": "2006-02-15T09:57:12Z",
+		"Staffs": {
+			"StaffID": 2,
+			"FirstName": "Jon",
+			"LastName": "Stephens",
+			"AddressID": 4,
+			"Email": "Jon.Stephens@sakilastaff.com",
+			"StoreID": 2,
+			"Active": true,
+			"Username": "Jon",
+			"Password": "8cb2237d0679ca88db6464eac60da96345513964",
+			"LastUpdate": "2006-05-16T16:13:11.79328Z",
+			"Picture": null,
+			"Store": null
+		}
+	}
+]
+`)
+}
+
 // In parameterized statements integer literals, like Int(num), are replaced with a placeholders. For some expressions,
 // postgres interpreter will not have enough information to deduce the type. If this is the case postgres returns an error.
 // Int8, Int16, .... functions will add automatic type cast over placeholder, so type deduction is always possible.