Golang PlaceholderInfo.Clear方法代碼示例

// golangFillQueryArguments populates the placeholder map with
// types and values from an array of Go values.
// TODO: This does not support arguments of the SQL 'Date' type, as there is not
// an equivalent type in Go's standard library. It's not currently needed by any
// of our internal tables.
func golangFillQueryArguments(pinfo *parser.PlaceholderInfo, args []interface{}) {
	pinfo.Clear()

	for i, arg := range args {
		k := fmt.Sprint(i + 1)
		if arg == nil {
			pinfo.SetValue(k, parser.DNull)
			continue
		}

		// A type switch to handle a few explicit types with special semantics:
		// - Datums are passed along as is.
		// - Time datatypes get special representation in the database.
		var d parser.Datum
		switch t := arg.(type) {
		case parser.Datum:
			d = t
		case time.Time:
			d = parser.MakeDTimestamp(t, time.Microsecond)
		case time.Duration:
			d = &parser.DInterval{Duration: duration.Duration{Nanos: t.Nanoseconds()}}
		case *inf.Dec:
			dd := &parser.DDecimal{}
			dd.Set(t)
			d = dd
		}
		if d == nil {
			// Handle all types which have an underlying type that can be stored in the
			// database.
			// Note: if this reflection becomes a performance concern in the future,
			// commonly used types could be added explicitly into the type switch above
			// for a performance gain.
			val := reflect.ValueOf(arg)
			switch val.Kind() {
			case reflect.Bool:
				d = parser.MakeDBool(parser.DBool(val.Bool()))
			case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
				d = parser.NewDInt(parser.DInt(val.Int()))
			case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
				d = parser.NewDInt(parser.DInt(val.Uint()))
			case reflect.Float32, reflect.Float64:
				d = parser.NewDFloat(parser.DFloat(val.Float()))
			case reflect.String:
				d = parser.NewDString(val.String())
			case reflect.Slice:
				// Handle byte slices.
				if val.Type().Elem().Kind() == reflect.Uint8 {
					d = parser.NewDBytes(parser.DBytes(val.Bytes()))
				}
			}
			if d == nil {
				panic(fmt.Sprintf("unexpected type %T", arg))
			}
		}
		pinfo.SetValue(k, d)
	}
}