fix(interactive): Fix Bugs of Alias Id in Union (#4404)

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## What do these changes do?
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Fixes #4385

interactive_engine/compiler/src/main/java/com/alibaba/graphscope/common/exception/FrontendException.java

@@ -65,7 +65,7 @@ public String getMessage() {
         StringBuilder sb = new StringBuilder();
         sb.append("ErrorCode: ").append(errorCode.name()).append("\n");
         String msg = super.getMessage();
-        if (!msg.endsWith("\n")) {
+        if (msg == null || !msg.endsWith("\n")) {
             msg += "\n";
         }
         sb.append("Message: ").append(msg);

interactive_engine/compiler/src/main/java/com/alibaba/graphscope/common/ir/type/GraphTypeFactoryImpl.java

@@ -22,8 +22,9 @@
 import com.google.common.collect.Maps;
 
 import org.apache.calcite.jdbc.JavaTypeFactoryImpl;
-import org.apache.calcite.rel.type.RelDataType;
+import org.apache.calcite.rel.type.*;
 import org.apache.calcite.rex.RexNode;
+import org.apache.calcite.util.Util;
 import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.nio.charset.Charset;
@@ -100,6 +101,46 @@ public RelDataType createArbitraryMapType(
         return super.leastRestrictive(types);
     }
 
+    /**
+     * reimplement the {@link RelDataTypeFactoryImpl#leastRestrictiveStructuredType(List)} method
+     * to maintain the original alias id in the input types
+     * @param types
+     * @return
+     */
+    @Override
+    protected @Nullable RelDataType leastRestrictiveStructuredType(final List<RelDataType> types) {
+        final RelDataType type0 = types.get(0);
+        if (!type0.isStruct()) {
+            return null;
+        }
+        final int fieldCount = type0.getFieldCount();
+        boolean isNullable = false;
+        for (RelDataType type : types) {
+            if (!type.isStruct()) {
+                return null;
+            }
+            if (type.getFieldList().size() != fieldCount) {
+                return null;
+            }
+            isNullable |= type.isNullable();
+        }
+        List<RelDataTypeField> fields = Lists.newArrayList();
+        for (int j = 0; j < fieldCount; ++j) {
+            final int k = j;
+            RelDataType type =
+                    leastRestrictive(Util.transform(types, t -> t.getFieldList().get(k).getType()));
+            if (type == null) {
+                return null;
+            }
+            fields.add(
+                    new RelDataTypeFieldImpl(
+                            type0.getFieldList().get(j).getName(),
+                            type0.getFieldList().get(j).getIndex(),
+                            type));
+        }
+        return new RelRecordType(StructKind.FULLY_QUALIFIED, fields, isNullable);
+    }
+
     // re-implement lease-restrictive type inference for arbitrary map types
     // for each key type and value type, check if they have a least-restrictive type, otherwise
     // return null

interactive_engine/compiler/src/test/java/com/alibaba/graphscope/gremlin/antlr4x/GraphBuilderTest.java

@@ -23,6 +23,8 @@
 import com.alibaba.graphscope.common.ir.planner.GraphIOProcessor;
 import com.alibaba.graphscope.common.ir.planner.GraphRelOptimizer;
 import com.alibaba.graphscope.common.ir.planner.rules.ExpandGetVFusionRule;
+import com.alibaba.graphscope.common.ir.rel.GraphLogicalProject;
+import com.alibaba.graphscope.common.ir.rex.RexGraphVariable;
 import com.alibaba.graphscope.common.ir.runtime.proto.RexToProtoConverter;
 import com.alibaba.graphscope.common.ir.tools.GraphBuilder;
 import com.alibaba.graphscope.common.ir.tools.GraphStdOperatorTable;
@@ -1852,4 +1854,36 @@ public void g_V_match_as_a_person_both_as_b_test() {
                         + " person]}], alias=[a], opt=[VERTEX])",
                 after3.explain().trim());
     }
+
+    @Test
+    public void union_valueMap_test() {
+        Configs configs =
+                new Configs(
+                        ImmutableMap.of(
+                                "graph.planner.is.on",
+                                "true",
+                                "graph.planner.opt",
+                                "CBO",
+                                "graph.planner.rules",
+                                "FilterIntoJoinRule, FilterMatchRule, ExtendIntersectRule,"
+                                        + " ExpandGetVFusionRule"));
+        GraphRelOptimizer optimizer = new GraphRelOptimizer(configs);
+        IrMeta irMeta =
+                Utils.mockIrMeta(
+                        "schema/ldbc.json",
+                        "statistics/ldbc30_statistics.json",
+                        optimizer.getGlogueHolder());
+        GraphBuilder builder = Utils.mockGraphBuilder(optimizer, irMeta);
+        RelNode node1 =
+                eval(
+                        "g.V().hasLabel(\"PERSON\").has(\"id\","
+                            + " 1816).union(outE(\"LIKES\").limit(10).as('a').inV().as('b').select('a','b').by(valueMap(\"creationDate\")),"
+                            + " outE(\"KNOWS\").limit(10).as('c').inV().as('d').select('c','d').by(valueMap(\"creationDate\")))",
+                        builder);
+        RelNode after1 = optimizer.optimize(node1, new GraphIOProcessor(builder, irMeta));
+        GraphLogicalProject project = (GraphLogicalProject) after1;
+        RexNode expr = project.getProjects().get(0);
+        RexGraphVariable var = (RexGraphVariable) expr;
+        Assert.assertEquals(2, var.getAliasId());
+    }
 }