[CALCITE-2074] Simplification of point ranges that are open above or …

…below yields wrong results

Suppose that R is a point range that is closed at one or both ends,
i.e. [x, x), or (x, x] or (x, y). Such a range is empty, but we were
wrongly simplifying it to a point. It is only valid to simplify
open-open ranges, [x, x], to a point. For example, "5 >= x AND x > 5",
described as the closed-open range "[5, 5)", should simplify to false.

core/src/main/java/org/apache/calcite/rex/RexSimplify.java

@@ -826,6 +826,12 @@ private <C extends Comparable<C>> RexNode simplifyUsingPredicates(RexNode e,
       // Term is always satisfied given these predicates
       return rexBuilder.makeLiteral(true);
     } else if (range2.lowerEndpoint().equals(range2.upperEndpoint())) {
+      if (range2.lowerBoundType() == BoundType.OPEN
+          || range2.upperBoundType() == BoundType.OPEN) {
+        // range is a point, but does not include its endpoint, therefore is
+        // effectively empty
+        return rexBuilder.makeLiteral(false);
+      }
       // range is now a point; it's worth simplifying
       return rexBuilder.makeCall(SqlStdOperatorTable.EQUALS, comparison.ref,
           rexBuilder.makeLiteral(range2.lowerEndpoint(),

core/src/test/java/org/apache/calcite/test/RexProgramTest.java

@@ -1411,6 +1411,30 @@ private void checkExponentialCnf(int n) {
         RelOptPredicateList.of(rexBuilder,
             ImmutableList.of(lt(bRef, literal10), ge(aRef, literal5))),
         ">(?0.a, 5)");
+
+    // condition "a > 5"
+    // with pre-condition "a <= 5"
+    // yields "false"
+    checkSimplifyFilter(gt(aRef, literal5),
+        RelOptPredicateList.of(rexBuilder,
+            ImmutableList.of(le(aRef, literal5))),
+        "false");
+
+    // condition "a > 5"
+    // with pre-condition "a <= 5 and b <= 5"
+    // yields "false"
+    checkSimplifyFilter(gt(aRef, literal5),
+        RelOptPredicateList.of(rexBuilder,
+            ImmutableList.of(le(aRef, literal5), le(bRef, literal5))),
+        "false");
+
+    // condition "a > 5 or b > 5"
+    // with pre-condition "a <= 5 and b <= 5"
+    // should yield "false" but yields "a = 5 or b = 5"
+    checkSimplifyFilter(or(gt(aRef, literal5), gt(bRef, literal5)),
+        RelOptPredicateList.of(rexBuilder,
+            ImmutableList.of(le(aRef, literal5), le(bRef, literal5))),
+        "false");
   }
 
   /** Unit test for