func simplifyComparisonExpr(n *parser.ComparisonExpr) (parser.TypedExpr, bool) {
// NormalizeExpr will have left comparisons in the form "<var> <op>
// <datum>" unless they could not be simplified further in which case
// simplifyExpr cannot handle them. For example, "lower(a) = 'foo'"
left, right := n.TypedLeft(), n.TypedRight()
if isVar(left) && isDatum(right) {
if right == parser.DNull {
switch n.Operator {
case parser.IsNotDistinctFrom:
switch left.(type) {
case *parser.IndexedVar:
// Transform "a IS NOT DISTINCT FROM NULL" into "a IS NULL".
return parser.NewTypedComparisonExpr(
parser.Is,
left,
right,
), true
}
case parser.IsDistinctFrom:
switch left.(type) {
case *parser.IndexedVar:
// Transform "a IS DISTINCT FROM NULL" into "a IS NOT NULL".
return parser.NewTypedComparisonExpr(
parser.IsNot,
left,
right,
), true
}
case parser.Is, parser.IsNot:
switch left.(type) {
case *parser.IndexedVar:
// "a IS {,NOT} NULL" can be used during index selection to restrict
// the range of scanned keys.
return n, true
}
default:
// All of the remaining comparison operators have the property that when
// comparing to NULL they evaluate to NULL (see evalComparisonOp). NULL is
// not the same as false, but in the context of a WHERE clause, NULL is
// considered not-true which is the same as false.
return parser.MakeDBool(false), true
}
}
switch n.Operator {
case parser.EQ:
// Translate "(a, b) = (1, 2)" to "(a, b) IN ((1, 2))".
switch left.(type) {
case *parser.Tuple:
return parser.NewTypedComparisonExpr(
parser.In,
left,
&parser.DTuple{right.(parser.Datum)},
), true
}
return n, true
case parser.NE, parser.GE, parser.LE:
return n, true
case parser.GT:
// This simplification is necessary so that subsequent transformation of
// > constraint to >= can use Datum.Next without concern about whether a
// next value exists. Note that if the variable (n.Left) is NULL, this
// comparison would evaluate to NULL which is equivalent to false for a
// boolean expression.
if right.(parser.Datum).IsMax() {
return parser.MakeDBool(false), true
}
return n, true
case parser.LT:
// Note that if the variable is NULL, this would evaluate to NULL which
// would equivalent to false for a boolean expression.
if right.(parser.Datum).IsMin() {
return parser.MakeDBool(false), true
}
return n, true
case parser.In, parser.NotIn:
tuple := *right.(*parser.DTuple)
if len(tuple) == 0 {
return parser.MakeDBool(false), true
}
return n, true
case parser.Like:
// a LIKE 'foo%' -> a >= "foo" AND a < "fop"
if d, ok := right.(*parser.DString); ok {
if i := strings.IndexAny(string(*d), "_%"); i >= 0 {
return makePrefixRange((*d)[:i], left, false), false
}
return makePrefixRange(*d, left, true), false
}
// TODO(pmattis): Support parser.DBytes?
case parser.SimilarTo:
// a SIMILAR TO "foo.*" -> a >= "foo" AND a < "fop"
if d, ok := right.(*parser.DString); ok {
pattern := parser.SimilarEscape(string(*d))
if re, err := regexp.Compile(pattern); err == nil {
prefix, complete := re.LiteralPrefix()
return makePrefixRange(parser.DString(prefix), left, complete), false
}
}
// TODO(pmattis): Support parser.DBytes?
}
}
return parser.MakeDBool(true), false
}
func simplifyOneAndInExpr(left, right *parser.ComparisonExpr) (parser.TypedExpr, parser.TypedExpr) {
if left.Operator != parser.In && right.Operator != parser.In {
panic(fmt.Sprintf("IN expression required: %s vs %s", left, right))
}
origLeft, origRight := left, right
switch left.Operator {
case parser.EQ, parser.NE, parser.GT, parser.GE, parser.LT, parser.LE, parser.Is:
switch right.Operator {
case parser.In:
left, right = right, left
}
fallthrough
case parser.In:
ltuple := *left.Right.(*parser.DTuple)
switch right.Operator {
case parser.Is:
if right.Right == parser.DNull {
return parser.MakeDBool(false), nil
}
case parser.EQ, parser.NE, parser.GT, parser.GE, parser.LT, parser.LE:
// Our tuple will be sorted (see simplifyComparisonExpr). Binary search
// for the right datum.
datum := right.Right.(parser.Datum)
i := sort.Search(len(ltuple), func(i int) bool {
return ltuple[i].(parser.Datum).Compare(datum) >= 0
})
switch right.Operator {
case parser.EQ:
if i < len(ltuple) && ltuple[i].Compare(datum) == 0 {
return right, nil
}
return parser.MakeDBool(false), nil
case parser.NE:
if i < len(ltuple) && ltuple[i].Compare(datum) == 0 {
if len(ltuple) < 2 {
return parser.MakeDBool(false), nil
}
ltuple = remove(ltuple, i)
}
return parser.NewTypedComparisonExpr(
parser.In,
left.TypedLeft(),
<uple,
), nil
case parser.GT:
if i < len(ltuple) {
if ltuple[i].Compare(datum) == 0 {
ltuple = ltuple[i+1:]
} else {
ltuple = ltuple[i:]
}
if len(ltuple) > 0 {
return parser.NewTypedComparisonExpr(
parser.In,
left.TypedLeft(),
<uple,
), nil
}
}
return parser.MakeDBool(false), nil
case parser.GE:
if i < len(ltuple) {
ltuple = ltuple[i:]
if len(ltuple) > 0 {
return parser.NewTypedComparisonExpr(
parser.In,
left.TypedLeft(),
<uple,
), nil
}
}
return parser.MakeDBool(false), nil
case parser.LT:
if i < len(ltuple) {
if i == 0 {
return parser.MakeDBool(false), nil
}
ltuple = ltuple[:i]
return parser.NewTypedComparisonExpr(
parser.In,
left.TypedLeft(),
<uple,
), nil
}
return left, nil
case parser.LE:
if i < len(ltuple) {
if ltuple[i].Compare(datum) == 0 {
i++
}
if i == 0 {
return parser.MakeDBool(false), nil
}
ltuple = ltuple[:i]
return parser.NewTypedComparisonExpr(
parser.In,
left.TypedLeft(),
<uple,
), nil
}
return left, nil
}
case parser.In:
// Both of our tuples are sorted. Intersect the lists.
rtuple := *right.Right.(*parser.DTuple)
intersection := intersectSorted(ltuple, rtuple)
if len(*intersection) == 0 {
return parser.MakeDBool(false), nil
}
return parser.NewTypedComparisonExpr(
parser.In,
left.TypedLeft(),
intersection,
), nil
}
}
return origLeft, origRight
}
func simplifyOneOrInExpr(left, right *parser.ComparisonExpr) (parser.TypedExpr, parser.TypedExpr) {
if left.Operator != parser.In && right.Operator != parser.In {
panic(fmt.Sprintf("IN expression required: %s vs %s", left, right))
}
origLeft, origRight := left, right
switch left.Operator {
case parser.EQ, parser.NE, parser.GT, parser.GE, parser.LT, parser.LE:
switch right.Operator {
case parser.In:
left, right = right, left
}
fallthrough
case parser.In:
tuple := *left.Right.(*parser.DTuple)
switch right.Operator {
case parser.EQ:
datum := right.Right.(parser.Datum)
// We keep the tuples for an IN expression in sorted order. So now we just
// merge the two sorted lists.
return parser.NewTypedComparisonExpr(
parser.In,
left.TypedLeft(),
mergeSorted(tuple, parser.DTuple{datum}),
), nil
case parser.NE, parser.GT, parser.GE, parser.LT, parser.LE:
datum := right.Right.(parser.Datum)
i := sort.Search(len(tuple), func(i int) bool {
return tuple[i].(parser.Datum).Compare(datum) >= 0
})
switch right.Operator {
case parser.NE:
if i < len(tuple) && tuple[i].Compare(datum) == 0 {
return makeIsNotNull(right.TypedLeft()), nil
}
return right, nil
case parser.GT:
if i == 0 {
// datum >= tuple[0]
if tuple[i].Compare(datum) == 0 {
// datum = tuple[0]
return parser.NewTypedComparisonExpr(
parser.GE,
left.TypedLeft(),
datum,
), nil
}
return right, nil
}
case parser.GE:
if i == 0 {
// datum >= tuple[0]
return right, nil
}
case parser.LT:
if i == len(tuple) {
// datum > tuple[len(tuple)-1]
return right, nil
} else if i == len(tuple)-1 {
// datum >= tuple[len(tuple)-1]
if tuple[i].Compare(datum) == 0 {
// datum == tuple[len(tuple)-1]
return parser.NewTypedComparisonExpr(
parser.LE,
left.TypedLeft(),
datum,
), nil
}
}
case parser.LE:
if i == len(tuple) ||
(i == len(tuple)-1 && tuple[i].Compare(datum) == 0) {
// datum >= tuple[len(tuple)-1]
return right, nil
}
}
case parser.In:
// We keep the tuples for an IN expression in sorted order. So now we
// just merge the two sorted lists.
return parser.NewTypedComparisonExpr(
parser.In,
left.TypedLeft(),
mergeSorted(tuple, *right.Right.(*parser.DTuple)),
), nil
}
}
return origLeft, origRight
}