func encodeEndConstraintDescending(
spans []roachpb.Span, c *parser.ComparisonExpr, isLastEndConstraint bool,
) {
switch c.Operator {
case parser.IsNot:
// An IS NOT NULL expressions allows us to constrain the end of the range
// to stop at NULL.
if c.Right != parser.DNull {
panic(fmt.Sprintf("expected NULL operand for IS NOT operator, found %v", c.Right))
}
for i := range spans {
spans[i].EndKey = encoding.EncodeNotNullDescending(spans[i].EndKey)
}
default:
datum := c.Right.(parser.Datum)
if c.Operator != parser.GT {
for i := range spans {
spans[i].EndKey = encodeInclusiveEndValue(
spans[i].EndKey, datum, encoding.Descending, isLastEndConstraint)
}
break
}
if !isLastEndConstraint {
panic(fmt.Sprintf("can't have other end constraints after a '>' constraint, found %v", c.Operator))
}
key, err := sqlbase.EncodeTableKey(nil, datum, encoding.Descending)
if err != nil {
panic(err)
}
// Append the constraint to all of the existing spans.
for i := range spans {
spans[i].EndKey = append(spans[i].EndKey, key...)
}
}
}
// Encodes datum at the end of key, using direction `dir` for the encoding.
// It takes in an inclusive key and returns an inclusive key if
// isLastEndConstraint is not set, and an exclusive key otherwise (the idea is
// that, for inclusive constraints, the value for the last column in the
// constraint needs to be adapted to an exclusive span.EndKey).
func encodeInclusiveEndValue(
key roachpb.Key, datum parser.Datum, dir encoding.Direction, isLastEndConstraint bool,
) roachpb.Key {
// Since the end of a span is exclusive, if the last constraint is an
// inclusive one, we might need to make the key exclusive by applying a
// PrefixEnd(). We normally avoid doing this by transforming "a = x" to
// "a = x±1" for the last end constraint, depending on the encoding direction
// (since this keeps the key nice and pretty-printable).
// However, we might not be able to do the ±1.
needExclusiveKey := false
if isLastEndConstraint {
if dir == encoding.Ascending {
if datum.IsMax() || !datum.HasNext() {
needExclusiveKey = true
} else {
datum = datum.Next()
}
} else {
if datum.IsMin() || !datum.HasPrev() {
needExclusiveKey = true
} else {
datum = datum.Prev()
}
}
}
key, err := sqlbase.EncodeTableKey(key, datum, dir)
if err != nil {
panic(err)
}
if needExclusiveKey {
key = key.PrefixEnd()
}
return key
}
func encodeStartConstraintDescending(spans []roachpb.Span, c *parser.ComparisonExpr) {
switch c.Operator {
case parser.Is:
// An IS NULL expressions allows us to constrain the start of the range
// to begin at NULL.
if c.Right != parser.DNull {
panic(fmt.Sprintf("expected NULL operand for IS operator, found %v", c.Right))
}
for i := range spans {
spans[i].Key = encoding.EncodeNullDescending(spans[i].Key)
}
case parser.NE:
panic("'!=' operators should have been transformed to 'IS NOT NULL'")
case parser.LE, parser.EQ:
datum := c.Right.(parser.Datum)
key, err := sqlbase.EncodeTableKey(nil, datum, encoding.Descending)
if err != nil {
panic(err)
}
// Append the constraint to all of the existing spans.
for i := range spans {
spans[i].Key = append(spans[i].Key, key...)
}
case parser.LT:
// A "<" constraint is the last start constraint. Since the constraint
// is exclusive and the start key is inclusive, we're going to apply
// a .PrefixEnd(). Note that a "<" is usually transformed to a "<=".
datum := c.Right.(parser.Datum)
key, err := sqlbase.EncodeTableKey(nil, datum, encoding.Descending)
if err != nil {
panic(err)
}
// Append the constraint to all of the existing spans.
for i := range spans {
spans[i].Key = append(spans[i].Key, key...)
spans[i].Key = spans[i].Key.PrefixEnd()
}
default:
panic(fmt.Sprintf("unexpected operator: %s", c))
}
}
// Splits spans according to a constraint like (...) in <tuple>.
// If the constraint is (a,b) IN ((1,2),(3,4)), each input span
// will be split into two: the first one will have "1/2" appended to
// the start and/or end, the second one will have "3/4" appended to
// the start and/or end.
//
// Returns the exploded spans.
func applyInConstraint(
spans []roachpb.Span,
c indexConstraint,
firstCol int,
index *sqlbase.IndexDescriptor,
isLastEndConstraint bool,
) []roachpb.Span {
var e *parser.ComparisonExpr
// It might be that the IN constraint is a start constraint, an
// end constraint, or both, depending on how whether we had
// start and end constraints for all the previous index cols.
if c.start != nil && c.start.Operator == parser.In {
e = c.start
} else {
e = c.end
}
tuple := *e.Right.(*parser.DTuple)
existingSpans := spans
spans = make([]roachpb.Span, 0, len(existingSpans)*len(tuple))
for _, datum := range tuple {
// start and end will accumulate the end constraint for
// the current element of the tuple.
var start, end []byte
switch t := datum.(type) {
case *parser.DTuple:
// The constraint is a tuple of tuples, meaning something like
// (...) IN ((1,2),(3,4)).
for j, tupleIdx := range c.tupleMap {
var err error
var colDir encoding.Direction
if colDir, err = index.ColumnDirections[firstCol+j].ToEncodingDirection(); err != nil {
panic(err)
}
if start, err = sqlbase.EncodeTableKey(start, (*t)[tupleIdx], colDir); err != nil {
panic(err)
}
end = encodeInclusiveEndValue(
end, (*t)[tupleIdx], colDir, isLastEndConstraint && (j == len(c.tupleMap)-1))
}
default:
// The constraint is a tuple of values, meaning something like
// a IN (1,2).
var colDir encoding.Direction
var err error
if colDir, err = index.ColumnDirections[firstCol].ToEncodingDirection(); err != nil {
panic(err)
}
if start, err = sqlbase.EncodeTableKey(nil, datum, colDir); err != nil {
panic(err)
}
end = encodeInclusiveEndValue(nil, datum, colDir, isLastEndConstraint)
// TODO(andrei): assert here that we end is not \xff\xff...
// encodeInclusiveEndValue sometimes calls key.PrefixEnd(),
// which doesn't work if the input is \xff\xff... However,
// that shouldn't happen: datum should not have that encoding.
}
for _, s := range existingSpans {
if c.start != nil {
s.Key = append(append(roachpb.Key(nil), s.Key...), start...)
}
if c.end != nil {
s.EndKey = append(append(roachpb.Key(nil), s.EndKey...), end...)
}
spans = append(spans, s)
}
}
return spans
}
