[CALCITE-6740] Case statements may generate too many same code

core/src/main/java/org/apache/calcite/adapter/enumerable/RexToLixTranslator.java

@@ -1522,6 +1522,7 @@ private static void implementRecursively(RexToLixTranslator currentTranslator,
         new BlockBuilder(true, currentBlockBuilder);
     final RexToLixTranslator ifTrueTranslator =
         currentTranslator.setBlock(ifTrueBlockBuilder);
+    ifTrueTranslator.rexResultMap.putAll(currentTranslator.rexResultMap);
     final Expression ifTrueRes =
         implementCallOperand2(ifTrueNode, storageTypes.get(pos + 1),
             ifTrueTranslator);
@@ -1542,6 +1543,7 @@ private static void implementRecursively(RexToLixTranslator currentTranslator,
         new BlockBuilder(true, currentBlockBuilder);
     final RexToLixTranslator ifFalseTranslator =
         currentTranslator.setBlock(ifFalseBlockBuilder);
+    ifFalseTranslator.rexResultMap.putAll(currentTranslator.rexResultMap);
     implementRecursively(ifFalseTranslator, operandList, valueVariable, pos + 2);
     final BlockStatement ifFalse = ifFalseBlockBuilder.toBlock();
     currentBlockBuilder.add(

core/src/test/java/org/apache/calcite/adapter/enumerable/CodeGeneratorTest.java

@@ -0,0 +1,100 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to you 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 org.apache.calcite.adapter.enumerable;
+
+import org.apache.calcite.jdbc.JavaTypeFactoryImpl;
+import org.apache.calcite.linq4j.tree.ClassDeclaration;
+import org.apache.calcite.linq4j.tree.Expressions;
+import org.apache.calcite.plan.ConventionTraitDef;
+import org.apache.calcite.plan.RelOptCluster;
+import org.apache.calcite.plan.RelTraitSet;
+import org.apache.calcite.plan.volcano.VolcanoPlanner;
+import org.apache.calcite.rel.RelNode;
+import org.apache.calcite.rel.RelRoot;
+import org.apache.calcite.rel.rules.CoreRules;
+import org.apache.calcite.rel.type.RelDataTypeFactory;
+import org.apache.calcite.rex.RexBuilder;
+import org.apache.calcite.sql.SqlNode;
+import org.apache.calcite.sql.parser.SqlParseException;
+import org.apache.calcite.sql.parser.SqlParser;
+import org.apache.calcite.sql.test.SqlTestFactory;
+import org.apache.calcite.sql.validate.SqlValidator;
+import org.apache.calcite.sql2rel.SqlToRelConverter;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.HashMap;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+
+/**
+ * Unit Tests for code generator.
+ */
+public class CodeGeneratorTest {
+
+  /** Test case for
+   * <a href="https://issues.apache.org/jira/browse/CALCITE-6740">[CALCITE-6740]
+   * Case statements may generate too many same code</a>. */
+  @Test public void testCaseWhen() throws SqlParseException {
+    String sql = "with \"t\" as (select case "
+        + "when \"store_id\" = 1 then '1' "
+        + "when \"store_id\" = 2 then '2' "
+        + "when \"store_id\" = 3 then '3' "
+        + "when \"store_id\" = 4 then '4' "
+        + "else '0' end as \"myid\" from (values (1),(2),(3),(6)) as \"tt\"(\"store_id\"))\n"
+        + "select case "
+        + "when \"myid\" = '1' then '11' "
+        + "when \"myid\" = '2' then '22' "
+        + "when \"myid\" = '3' then '33' "
+        + "when \"myid\" = '4' then '44' "
+        + "else '0' end as \"res\" from \"t\"";
+
+    VolcanoPlanner planner = new VolcanoPlanner();
+    planner.addRelTraitDef(ConventionTraitDef.INSTANCE);
+    planner.addRule(CoreRules.PROJECT_TO_CALC);
+    planner.addRule(EnumerableRules.ENUMERABLE_CALC_RULE);
+    planner.addRule(EnumerableRules.ENUMERABLE_VALUES_RULE);
+
+    SqlTestFactory factory = SqlTestFactory.INSTANCE.withPlannerFactory(context -> planner);
+    SqlParser parser = factory.createParser(sql);
+    SqlNode sqlNode = parser.parseQuery();
+    SqlToRelConverter converter = factory.createSqlToRelConverter();
+    SqlValidator validator = converter.validator;
+    SqlNode validated = validator.validate(sqlNode);
+    RelRoot relRoot = converter.convertQuery(validated, false, true);
+
+    RelDataTypeFactory typeFactory =
+        new JavaTypeFactoryImpl(org.apache.calcite.rel.type.RelDataTypeSystem.DEFAULT);
+    RelOptCluster cluster = RelOptCluster.create(planner, new RexBuilder(typeFactory));
+    RelTraitSet desiredTraits =
+        cluster.traitSet().replace(EnumerableConvention.INSTANCE);
+
+    RelNode rel = planner.changeTraits(relRoot.rel, desiredTraits);
+    planner.setRoot(rel);
+
+    EnumerableRel plan = (EnumerableRel) planner.findBestExp();
+    EnumerableRelImplementor relImplementor =
+        new EnumerableRelImplementor(plan.getCluster().getRexBuilder(), new HashMap<>());
+    ClassDeclaration classExpr = relImplementor.implementRoot(plan, EnumerableRel.Prefer.ARRAY);
+    String javaCode =
+        Expressions.toString(classExpr.memberDeclarations, "\n", false);
+    assertFalse(javaCode.contains("case_when_value1"));
+    assertFalse(javaCode.contains("case_when_value2"));
+    assertFalse(javaCode.contains("case_when_value3"));
+    assertFalse(javaCode.contains("case_when_value4"));
+  }
+}