[CALCITE-6607] RexExecutor can throw during evaluation

Signed-off-by: Mihai Budiu <mbudiu@feldera.com>

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

@@ -126,25 +126,33 @@ public static RexExecutable getExecutable(RexBuilder rexBuilder, List<RexNode> e
 
   /**
    * Do constant reduction using generated code.
+   *
+   * @param rexBuilder Builder used to construct expressions
+   * @param constExps  A list of constant expressions
+   * @param reducedValues  An empty list.  The function will return
+   *                       for each expression on constExps one equivalent
+   *                       reduced expression in this list, in the same order.
    */
   @Override public void reduce(RexBuilder rexBuilder, List<RexNode> constExps,
       List<RexNode> reducedValues) {
-    String code;
+    assert reducedValues.isEmpty();
     try {
-      code = compile(rexBuilder, constExps, (list, index, storageType) -> {
+      String code = compile(rexBuilder, constExps, (list, index, storageType) -> {
         throw new UnsupportedOperationException();
       });
+
+      final RexExecutable executable = new RexExecutable(code, constExps);
+      executable.setDataContext(dataContext);
+      executable.reduce(rexBuilder, constExps, reducedValues);
     } catch (RuntimeException ex) {
-      // Give up on reduction and return expressions unchanged.
+      // Something went wrong during constant reduction (for example,
+      // we may have attempted a division by zero).
+      // Give up doing the reduction and return constExps unchanged.
       // This effectively moves the error from compile time to runtime.
       // We could give a warning here if there was a mechanism for warnings.
+      reducedValues.clear();
       reducedValues.addAll(constExps);
-      return;
     }
-
-    final RexExecutable executable = new RexExecutable(code, constExps);
-    executable.setDataContext(dataContext);
-    executable.reduce(rexBuilder, constExps, reducedValues);
   }
 
   /**