Method TypeModifier

pkg/sql/types/types.go:1396–1432

TypeModifier returns the type modifier of the type. This corresponds to the pg_attribute.atttypmod column. atttypmod records type-specific data supplied at table creation time (for example, the maximum length of a varchar column). Array types have the same type modifier as the contents of the array.

()

// Array types have the same type modifier as the contents of the array.
// The value will be -1 for types that do not need atttypmod.
func (t *T) TypeModifier() int32 {
	if t.Family() == ArrayFamily {
		return t.ArrayContents().TypeModifier()
	}
	// The type modifier for "char" is always -1.
	if t.Oid() == oid.T_char {
		return int32(-1)
	}

	switch t.Family() {
	case StringFamily, CollatedStringFamily:
		if width := t.Width(); width != 0 {
			// Postgres adds 4 to the attypmod for bounded string types, the
			// var header size.
			return width + 4
		}
	case BitFamily, PGVectorFamily:
		if width := t.Width(); width != 0 {
			return width
		}
	case TimestampFamily, TimestampTZFamily, TimeFamily, TimeTZFamily, IntervalFamily:
		// For timestamp the precision is the type modifier value.
		if !t.InternalType.TimePrecisionIsSet {
			return -1
		}
		return t.Precision()
	case DecimalFamily:
		// attTypMod is calculated by putting the precision in the upper
		// bits and the scale in the lower bits of a 32-bit int, and adding
		// 4 (the var header size). We mock this for clients' sake. See
		// https://github.com/postgres/postgres/blob/5a2832465fd8984d089e8c44c094e6900d987fcd/src/backend/utils/adt/numeric.c#L1242.
		if width, precision := t.Width(), t.Precision(); precision != 0 || width != 0 {
			return ((precision << 16) | width) + 4
		}
	}
	return int32(-1)
}

// WithoutTypeModifiers returns a copy of the given type with the type modifiers
// reset, if the type has modifiers. The returned type has arbitrary width and