func newSargableLike(expr expression.BinaryFunction, re *regexp.Regexp) *sargableLike {
rv := &sargableLike{}
rv.test = func(expr2 expression.Expression) (bool, error) {
return expr.EquivalentTo(expr2) || expr.First().EquivalentTo(expr2), nil
}
return rv
}
func newSargLike(expr expression.BinaryFunction, re *regexp.Regexp) expression.Visitor {
prefix := ""
if re != nil {
prefix, complete := re.LiteralPrefix()
if complete {
eq := expression.NewEq(expr.First(), expression.NewConstant(prefix))
return newSargEq(eq.(*expression.Eq))
}
}
rv := &sargLike{}
rv.sarg = func(expr2 expression.Expression) (Spans, error) {
if expr.EquivalentTo(expr2) {
return _SELF_SPANS, nil
}
if !expr.First().EquivalentTo(expr2) {
return nil, nil
}
span := &Span{}
span.Range.Low = expression.Expressions{expression.NewConstant(prefix)}
last := len(prefix) - 1
if last >= 0 && prefix[last] < math.MaxUint8 {
bytes := []byte(prefix)
bytes[last]++
span.Range.High = expression.Expressions{expression.NewConstant(string(bytes))}
} else {
span.Range.High = _EMPTY_ARRAY
}
span.Range.Inclusion = datastore.LOW
return Spans{span}, nil
}
return rv
}