Function AdjustValueToType

pkg/sql/sem/tree/datum.go:6389–6574

AdjustValueToType checks that the width (for strings, byte arrays, and bit strings) and scale (decimal). and, shape/srid (for geospatial types) fits the specified column type. Additionally, some precision truncation may occur for the specified column type. In case of decimals, it can truncate frac

(typ *types.T, inVal Datum)

// the width of the value is wider than a single character. For this exception,
// AdjustValueToType performs the truncation itself.
func AdjustValueToType(typ *types.T, inVal Datum) (outVal Datum, err error) {
	switch typ.Family() {
	case types.StringFamily, types.CollatedStringFamily:
		var sv string
		if v, ok := AsDString(inVal); ok {
			sv = string(v)
		} else if v, ok := inVal.(*DCollatedString); ok {
			sv = v.Contents
		}
		switch typ.Oid() {
		case oid.T_char:
			// "char" is supposed to truncate long values.
			sv = util.TruncateString(sv, 1)
		case oid.T_bpchar:
			// bpchar types truncate trailing whitespace.
			sv = strings.TrimRight(sv, " ")
		}

		var overlength int
		// Fast path. Check for skip counting the number of runes through iteration.
		if typ.Width() > 0 && len(sv) > int(typ.Width()) {
			overlength = utf8.RuneCountInString(sv) - int(typ.Width())
		} else {
			overlength = 0
		}
		if typ.Oid() == oid.T_varchar {
			// varchar types truncate extra trailing whitespace when
			// more characters than the varchar size are provided.
			for overlength > 0 {
				if sv[len(sv)-1] != ' ' {
					break
				}
				sv = sv[:len(sv)-1]
				overlength--
			}
		}
		if overlength > 0 {
			return nil, pgerror.Newf(pgcode.StringDataRightTruncation,
				"value too long for type %s",
				typ.SQLString())
		}

		if typ.Oid() == oid.T_bpchar || typ.Oid() == oid.T_char || typ.Oid() == oid.T_varchar {
			if _, ok := AsDString(inVal); ok {
				return NewDString(sv), nil
			} else if _, ok := inVal.(*DCollatedString); ok {
				return NewDCollatedString(sv, typ.Locale(), &CollationEnvironment{})
			}
		}
	case types.IntFamily:
		if v, ok := AsDInt(inVal); ok {
			if typ.Width() == 32 || typ.Width() == 16 {
				// Width is defined in bits.
				width := uint(typ.Width() - 1)

				// We're performing range checks in line with Go's
				// implementation of math.(Max|Min)(16|32) numbers that store
				// the boundaries of the allowed range.