Method Prev

pkg/sql/sem/tree/datum.go:4617–4645

Prev implements the Datum interface.

(ctx context.Context, cmpCtx CompareContext)

// Prev implements the Datum interface.
func (d *DTuple) Prev(ctx context.Context, cmpCtx CompareContext) (Datum, bool) {
	// Note: (a:decimal, b:int, c:int) has a prev value; that's (a, b,
	// c-1). With an exception if c is MinInt64, in which case the prev
	// value is (a, b-1, max(_ *EvalContext)). However, (a:int, b:decimal) does not
	// have a prev value, because decimal doesn't have one.
	//
	// In general, a tuple has a prev value if and only if it ends with
	// zero or more values that are a minimum and a maximum value of the
	// same type exists, and the first element before that has a prev
	// value.
	res := NewDTupleWithLen(d.typ, len(d.D))
	copy(res.D, d.D)
	for i := len(res.D) - 1; i >= 0; i-- {
		if !res.D[i].IsMin(ctx, cmpCtx) {
			prevVal, ok := res.D[i].Prev(ctx, cmpCtx)
			if !ok {
				return nil, false
			}
			res.D[i] = prevVal
			break
		}
		maxVal, ok := res.D[i].Max(ctx, cmpCtx)
		if !ok {
			return nil, false
		}
		res.D[i] = maxVal
	}
	return res, true
}

// Next implements the Datum interface.
func (d *DTuple) Next(ctx context.Context, cmpCtx CompareContext) (Datum, bool) {