diff --git a/core/src/main/java/org/apache/calcite/rex/RexSimplify.java b/core/src/main/java/org/apache/calcite/rex/RexSimplify.java
index d3c1f93aa53..312e61b1dcf 100644
--- a/core/src/main/java/org/apache/calcite/rex/RexSimplify.java
+++ b/core/src/main/java/org/apache/calcite/rex/RexSimplify.java
@@ -2060,6 +2060,26 @@ private RexNode simplifyOrs(List<RexNode> terms, RexUnknownAs unknownAs) {
           }
         }
         break;
+      case IS_NOT_TRUE:
+        RexNode arg = ((RexCall) term).getOperands().get(0);
+        if (isSafeExpression(arg) && terms.contains(arg)) {
+          return trueLiteral;
+        }
+        break;
+      case NOT:
+        RexNode x = ((RexCall) term).getOperands().get(0);
+        if (isSafeExpression(x) && terms.contains(x)) {
+          if (!x.getType().isNullable()) {
+            return trueLiteral;
+          }
+
+          final RexNode isNotNull =
+              rexBuilder.makeCall(SqlStdOperatorTable.IS_NOT_NULL, x);
+          terms.set(terms.indexOf(x), simplifyIs((RexCall) isNotNull, unknownAs));
+          terms.set(i, rexBuilder.makeNullLiteral(x.getType()));
+          i--;
+        }
+        break;
       default:
         break;
       }
diff --git a/core/src/test/java/org/apache/calcite/rex/RexProgramTest.java b/core/src/test/java/org/apache/calcite/rex/RexProgramTest.java
index e4775935ef7..ba7e4f18bf5 100644
--- a/core/src/test/java/org/apache/calcite/rex/RexProgramTest.java
+++ b/core/src/test/java/org/apache/calcite/rex/RexProgramTest.java
@@ -2318,7 +2318,7 @@ trueLiteral, literal(2),
             isTrue(vBool()), literal(1),
             isNotTrue(vBool()), literal(1),
             literal(2)),
-        "CASE(OR(?0.bool0, IS NOT TRUE(?0.bool0)), 1, 2)");
+        "1");
   }
 
   @Test void testSimplifyCaseBranchesCollapse2() {
@@ -3304,6 +3304,48 @@ private static String getString(Map<RexNode, RexNode> map) {
         "IS NULL(?0.int1)");
   }
 
+  /** Unit test for
+   * <a href="https://issues.apache.org/jira/browse/CALCITE-4189">[CALCITE-4189]
+   * Simplify 'p OR (p IS NOT TRUE)' to 'TRUE'</a>. */
+  @Test public void testSimplifyOrNot2() {
+    final SqlOperator func =
+        SqlBasicFunction.create("func", ReturnTypes.BOOLEAN_NULLABLE, OperandTypes.VARIADIC);
+    final RexNode unsafeRel = rexBuilder.makeCall(func, div(vInt(0), literal(2)));
+    // x OR x IS NOT TRUE ==> "true"
+    checkSimplify(or(vBool(), isNotTrue(vBool())), "true");
+    checkSimplify(or(vBoolNotNull(), isNotTrue(vBoolNotNull())), "true");
+    // outside unsafe expression will not prevent simplification
+    checkSimplify(or(unsafeRel, vBool(), isNotTrue(vBool())), "true");
+
+    // x OR NOT x ==> "true" (if x is not nullable)
+    checkSimplify(or(vBoolNotNull(), not(vBoolNotNull())), "true");
+    checkSimplify(or(unsafeRel, vBoolNotNull(), not(vBoolNotNull())), "true");
+
+    // x OR NOT x ==> x IS NOT NULL OR NULL (if x is nullable)
+    checkSimplify3(or(vBool(), not(vBool())),
+        "OR(IS NOT NULL(?0.bool0), null)",
+        "IS NOT NULL(?0.bool0)",
+        "true");
+    checkSimplify3(or(unsafeRel, vBool(), not(vBool())),
+        "OR(func(/(?0.int0, 2)), IS NOT NULL(?0.bool0), null)",
+        "OR(func(/(?0.int0, 2)), IS NOT NULL(?0.bool0))",
+        "true");
+    // remove all redundant NULL
+    checkSimplify3(or(vBool(0), not(vBool(0)), vBool(1), not(vBool(1))),
+        "OR(IS NOT NULL(?0.bool0), null, IS NOT NULL(?0.bool1))",
+        "OR(IS NOT NULL(?0.bool0), IS NOT NULL(?0.bool1))",
+        "true");
+
+    // unsafe expression can not be simplified
+    checkSimplify3(or(unsafeRel, isNotTrue(unsafeRel)),
+        "OR(func(/(?0.int0, 2)), IS NOT TRUE(func(/(?0.int0, 2))))",
+        "OR(func(/(?0.int0, 2)), IS NOT TRUE(func(/(?0.int0, 2))))",
+        "OR(func(/(?0.int0, 2)), NOT(func(/(?0.int0, 2))))");
+    checkSimplifyUnchanged(or(unsafeRel, not(unsafeRel)));
+
+    checkSimplify(or(unsafeRel, trueLiteral), "true");
+  }
+
   private void checkSarg(String message, Sarg sarg,
       Matcher<Integer> complexityMatcher, Matcher<String> stringMatcher) {
     assertThat(message, sarg.complexity(), complexityMatcher);
diff --git a/geode/src/main/java/org/apache/calcite/adapter/geode/rel/GeodeFilter.java b/geode/src/main/java/org/apache/calcite/adapter/geode/rel/GeodeFilter.java
index afdc6e468b7..0a401fdfc06 100644
--- a/geode/src/main/java/org/apache/calcite/adapter/geode/rel/GeodeFilter.java
+++ b/geode/src/main/java/org/apache/calcite/adapter/geode/rel/GeodeFilter.java
@@ -320,6 +320,9 @@ private String translateMatch2(RexNode node) {
         return translateBinary(">=", "<=", (RexCall) node);
       case INPUT_REF:
         return translateBinary2("=", node, rexBuilder.makeLiteral(true));
+      case IS_NOT_NULL:
+        child = ((RexCall) node).getOperands().get(0);
+        return translateBinary2("<>", child, rexBuilder.makeNullLiteral(node.getType()));
       case NOT:
         child = ((RexCall) node).getOperands().get(0);
         if (child.getKind() == SqlKind.CAST) {
diff --git a/geode/src/main/java/org/apache/calcite/adapter/geode/rel/GeodeRules.java b/geode/src/main/java/org/apache/calcite/adapter/geode/rel/GeodeRules.java
index 5fa2b563402..b407d368088 100644
--- a/geode/src/main/java/org/apache/calcite/adapter/geode/rel/GeodeRules.java
+++ b/geode/src/main/java/org/apache/calcite/adapter/geode/rel/GeodeRules.java
@@ -41,6 +41,7 @@
 import org.apache.calcite.sql.validate.SqlValidatorUtil;
 
 import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableList;
 
 import org.immutables.value.Value;
 
@@ -314,10 +315,7 @@ private static boolean isEqualityOnKey(RexNode node, List<String> fieldNames) {
 
     private static boolean isBooleanColumnReference(RexNode node, List<String> fieldNames) {
       // FIXME Ignore casts for rel and assume they aren't really necessary
-      if (node.isA(SqlKind.CAST)) {
-        node = ((RexCall) node).getOperands().get(0);
-      }
-      if (node.isA(SqlKind.NOT)) {
+      while (node.isA(ImmutableList.of(SqlKind.NOT, SqlKind.CAST, SqlKind.IS_NOT_NULL))) {
         node = ((RexCall) node).getOperands().get(0);
       }
       if (node.isA(SqlKind.INPUT_REF)) {
diff --git a/geode/src/test/java/org/apache/calcite/adapter/geode/rel/GeodeAllDataTypesTest.java b/geode/src/test/java/org/apache/calcite/adapter/geode/rel/GeodeAllDataTypesTest.java
index edbce076cca..dafec6efac0 100644
--- a/geode/src/test/java/org/apache/calcite/adapter/geode/rel/GeodeAllDataTypesTest.java
+++ b/geode/src/test/java/org/apache/calcite/adapter/geode/rel/GeodeAllDataTypesTest.java
@@ -110,6 +110,16 @@ private CalciteAssert.AssertThat calciteAssert() {
                 + "WHERE booleanValue = true"));
   }
 
+  @Test void testSqlBooleanColumnIsNotNullFilter() {
+    calciteAssert()
+        .query("SELECT booleanValue as booleanValue "
+            + "FROM geode.allDataTypesRegion WHERE booleanValue is not null")
+        .returnsCount(3)
+        .queryContains(
+            GeodeAssertions.query("SELECT booleanValue AS booleanValue FROM /allDataTypesRegion "
+                + "WHERE booleanValue <> null"));
+  }
+
   @Test void testSqlBooleanColumnFilter() {
     calciteAssert()
         .query("SELECT booleanValue as booleanValue "