Fix potential NPE due to exception not having an underlying message (#3302)

This introduces a new exception at the Record Layer level:
`UnableToPlanException`. That exception is translated at the Relational
Layer level into the SQL error code `UNSUPPORTED_OPERATION`.

Author: arnaud-lacurie

fdb-record-layer-core/src/main/java/com/apple/foundationdb/record/query/plan/cascades/CascadesPlanner.java

@@ -381,7 +381,7 @@ private RecordQueryPlan resultOrFail() {
             }
             return (RecordQueryPlan)singleRoot;
         } else {
-            throw new RecordCoreException("Cascades planner could not plan query")
+            throw new UnableToPlanException("Cascades planner could not plan query")
                     .addLogInfo("finalExpression", currentRoot.get());
         }
     }

fdb-record-layer-core/src/main/java/com/apple/foundationdb/record/query/plan/cascades/UnableToPlanException.java

@@ -0,0 +1,39 @@
+/*
+ * UnableToPlanException.java
+ *
+ * This source file is part of the FoundationDB open source project
+ *
+ * Copyright 2025 Apple Inc. and the FoundationDB project authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.apple.foundationdb.record.query.plan.cascades;
+
+import com.apple.foundationdb.annotation.API;
+import com.apple.foundationdb.record.RecordCoreException;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+/**
+ * Error being thrown when Cascades cannot plan a query.
+ */
+@API(API.Status.EXPERIMENTAL)
+public class UnableToPlanException extends RecordCoreException {
+    private static final long serialVersionUID = -640771754012134420L;
+
+    public UnableToPlanException(@Nonnull String msg, @Nullable Object ... keyValues) {
+        super(msg, keyValues);
+    }
+}

fdb-record-layer-core/src/test/java/com/apple/foundationdb/record/provider/foundationdb/query/FDBNestedRepeatedQueryTest.java

@@ -60,6 +60,7 @@
 import com.apple.foundationdb.record.query.plan.cascades.GraphExpansion;
 import com.apple.foundationdb.record.query.plan.cascades.Quantifier;
 import com.apple.foundationdb.record.query.plan.cascades.Reference;
+import com.apple.foundationdb.record.query.plan.cascades.UnableToPlanException;
 import com.apple.foundationdb.record.query.plan.cascades.expressions.ExplodeExpression;
 import com.apple.foundationdb.record.query.plan.cascades.expressions.GroupByExpression;
 import com.apple.foundationdb.record.query.plan.cascades.expressions.LogicalSortExpression;
@@ -2005,7 +2006,7 @@ private Quantifier explodeEntryQun(@Nonnull Quantifier outerQun, @Nonnull String
     }
 
     private void assertFailsToPlan(@Nonnull Supplier<Reference> querySupplier, String... allowedIndexes) {
-        final RecordCoreException rce = assertThrows(RecordCoreException.class, () -> planGraph(querySupplier, allowedIndexes));
+        final RecordCoreException rce = assertThrows(UnableToPlanException.class, () -> planGraph(querySupplier, allowedIndexes));
         assertThat(rce.getMessage(), containsString("Cascades planner could not plan query"));
     }
 

fdb-record-layer-core/src/test/java/com/apple/foundationdb/record/provider/foundationdb/query/GroupByTest.java

@@ -22,7 +22,6 @@
 
 import com.apple.foundationdb.record.Bindings;
 import com.apple.foundationdb.record.EvaluationContext;
-import com.apple.foundationdb.record.RecordCoreException;
 import com.apple.foundationdb.record.RecordCursor;
 import com.apple.foundationdb.record.TestRecords1Proto;
 import com.apple.foundationdb.record.metadata.Index;
@@ -41,6 +40,7 @@
 import com.apple.foundationdb.record.query.plan.cascades.GraphExpansion;
 import com.apple.foundationdb.record.query.plan.cascades.Quantifier;
 import com.apple.foundationdb.record.query.plan.cascades.Reference;
+import com.apple.foundationdb.record.query.plan.cascades.UnableToPlanException;
 import com.apple.foundationdb.record.query.plan.cascades.expressions.FullUnorderedScanExpression;
 import com.apple.foundationdb.record.query.plan.cascades.expressions.GroupByExpression;
 import com.apple.foundationdb.record.query.plan.cascades.expressions.LogicalSortExpression;
@@ -129,7 +129,7 @@ public void testSimpleGroupBy() {
     public void attemptToPlanGroupByWithoutCompatiblySortedIndexFails() {
         setupHookAndAddData(false, false);
         final var cascadesPlanner = (CascadesPlanner)planner;
-        Assertions.assertThrows(RecordCoreException.class, () -> cascadesPlanner.planGraph(
+        Assertions.assertThrows(UnableToPlanException.class, () -> cascadesPlanner.planGraph(
                 () -> constructGroupByPlan(false, false, GroupingKind.REGULAR_GROUPING),
                 Optional.empty(),
                 IndexQueryabilityFilter.TRUE,

fdb-relational-core/src/main/java/com/apple/foundationdb/relational/recordlayer/util/ExceptionUtil.java

@@ -28,6 +28,7 @@
 import com.apple.foundationdb.record.provider.foundationdb.FDBExceptions;
 import com.apple.foundationdb.record.provider.foundationdb.RecordAlreadyExistsException;
 import com.apple.foundationdb.record.query.plan.cascades.SemanticException;
+import com.apple.foundationdb.record.query.plan.cascades.UnableToPlanException;
 import com.apple.foundationdb.relational.api.exceptions.ErrorCode;
 import com.apple.foundationdb.relational.api.exceptions.UncheckedRelationalException;
 import com.apple.foundationdb.relational.api.exceptions.RelationalException;
@@ -80,7 +81,7 @@ private static RelationalException recordCoreToRelationalException(RecordCoreExc
             } else {
                 code = ErrorCode.INTERNAL_ERROR;
             }
-        } else if (re.getMessage().contains("Cascades planner could not plan query")) {
+        } else if (re instanceof UnableToPlanException) {
             code = ErrorCode.UNSUPPORTED_QUERY;
         }