[GitHub] [calcite] soumyakanti3578 commented on a change in pull request #2482: CALCITE-4702 - Error when executing query with GROUP BY constant via JDBC adapter

[GitBox <gi...@apache.org>]

soumyakanti3578 commented on a change in pull request #2482:
URL: https://github.com/apache/calcite/pull/2482#discussion_r745820974



##########
File path: core/src/main/java/org/apache/calcite/rel/rules/GroupByConstantAddJoinRule.java
##########
@@ -0,0 +1,205 @@
+/*
+ * 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.rel.rules;
+
+import org.apache.calcite.plan.RelOptRuleCall;
+import org.apache.calcite.plan.RelRule;
+import org.apache.calcite.rel.core.Aggregate;
+import org.apache.calcite.rel.core.Join;
+import org.apache.calcite.rel.core.JoinRelType;
+import org.apache.calcite.rel.core.Project;
+import org.apache.calcite.rel.logical.LogicalAggregate;
+import org.apache.calcite.rel.logical.LogicalProject;
+import org.apache.calcite.rel.logical.LogicalValues;
+import org.apache.calcite.rel.type.RelDataTypeFactory;
+import org.apache.calcite.rex.RexBuilder;
+import org.apache.calcite.rex.RexInputRef;
+import org.apache.calcite.rex.RexLiteral;
+import org.apache.calcite.rex.RexNode;
+import org.apache.calcite.sql.type.SqlTypeFamily;
+import org.apache.calcite.sql.type.SqlTypeName;
+import org.apache.calcite.tools.RelBuilder;
+import org.apache.calcite.tools.RelBuilderFactory;
+import org.apache.calcite.util.Pair;
+
+import com.google.common.collect.ImmutableList;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Planner rule that recognizes  a {@link org.apache.calcite.rel.core.Aggregate}
+ * on top of a {@link org.apache.calcite.rel.core.Project} where the aggregate's group set
+ * contains boolean literals (true, false), and removes the literals from the group keys by joining
+ * with a dummy table of boolean literals.
+ *
+ * select avg(sal)
+ * from emp
+ * group by true;
+ *
+ * becomes
+ *
+ * select avg(sal)
+ * from emp, (select true x) dummy
+ * group by dummy.x;
+ */
+public class GroupByConstantAddJoinRule
+    extends RelRule<GroupByConstantAddJoinRule.Config> {
+
+  /**
+   * Creates a RelRule.
+   *
+   */
+  protected GroupByConstantAddJoinRule(Config config) {
+    super(config);
+  }
+
+  @Deprecated // to be removed before 2.0
+  public GroupByConstantAddJoinRule(
+      Class<? extends Aggregate> aggregateClass,
+      Class<? extends Project> projectClass,
+      RelBuilderFactory relBuilderFactory) {
+    this(CoreRules.GROUP_BY_CONSTANT_ADD_JOIN_RULE.config
+        .withRelBuilderFactory(relBuilderFactory)
+        .as(Config.class)
+        .withOperandFor(aggregateClass, projectClass));
+  }
+
+  public boolean matches(RelOptRuleCall call) {
+    final Aggregate aggregate = call.rel(0);
+    final Project project = call.rel(1);
+
+    // avoids transforming correlated queries
+    if (aggregate.getAggCallList().size() == 0) {
+      return false;
+    }
+
+    boolean hasBooleanLiteral = false;
+
+    for (int groupKey: aggregate.getGroupSet().asList()) {
+      if (groupKey >= aggregate.getRowType().getFieldCount()) {
+        continue;
+      }
+      hasBooleanLiteral = (aggregate.getRowType().getFieldList().get(groupKey).getType().getFamily()
+          == SqlTypeFamily.BOOLEAN)
+          && (project.getProjects().get(groupKey) instanceof RexLiteral);
+
+      if (hasBooleanLiteral) {
+        return true;
+      }
+    }
+
+    return hasBooleanLiteral;
+  }
+
+  private LogicalValues getValues(Aggregate aggregate, Project project, RexBuilder rexBuilder,
+      RelBuilder builder) {
+    final ImmutableList.Builder<ImmutableList<RexLiteral>> tuples =
+        ImmutableList.builder();
+    ImmutableList.Builder<RexLiteral> b = ImmutableList.builder();
+    boolean truePresent = false;
+    boolean falsePresent = false;
+
+    for (int groupKey: aggregate.getGroupSet().asList()) {
+      if (project.getProjects().get(groupKey) instanceof RexLiteral) {
+        if (project.getProjects().get(groupKey).isAlwaysTrue()) {
+          truePresent = true;
+        }
+        if (project.getProjects().get(groupKey).isAlwaysFalse()) {
+          falsePresent = true;
+        }
+      }
+    }
+
+    RelDataTypeFactory.Builder relDataTypeBuilder = rexBuilder.getTypeFactory().builder();
+    if (truePresent) {
+      b.add(rexBuilder.makeLiteral(true));
+      relDataTypeBuilder.add("T", SqlTypeName.BOOLEAN);
+    }
+    if (falsePresent) {
+      b.add(rexBuilder.makeLiteral(false));
+      relDataTypeBuilder.add("F", SqlTypeName.BOOLEAN);
+    }
+    tuples.add(b.build());
+    LogicalValues values = LogicalValues.create(builder.getCluster(), relDataTypeBuilder.build(),
+        tuples.build());
+
+    return values;
+  }
+
+  @Override public void onMatch(RelOptRuleCall call) {
+    final Aggregate aggregate = call.rel(0);
+    final Project project = call.rel(1);
+
+    RelBuilder builder = call.builder();
+    RexBuilder rexBuilder = builder.getRexBuilder();
+
+    builder.push(project.getInput());
+    LogicalValues values = getValues(aggregate, project, rexBuilder, builder);
+    builder.push(values);
+
+    builder.join(JoinRelType.INNER, rexBuilder.makeLiteral(true));
+    Join join = (Join) builder.build();
+
+    List<RexNode> newProjects = new ArrayList<>();
+    List<String> names = new ArrayList<>();
+
+    int falseIndex = join.getRowType().getFieldCount() - 1;
+    int trueIndex = join.getRight().getRowType().getFieldCount() == 1
+        ? falseIndex : falseIndex - 1;
+    for (Pair<RexNode, String> pair: project.getNamedProjects()) {
+      if (pair.getKey() instanceof RexLiteral) {
+        if (pair.getKey().isAlwaysTrue()) {
+          newProjects.add(RexInputRef.of(trueIndex, join.getRowType()));
+          names.add(join.getRowType().getFieldList().get(trueIndex).getName());
+        }
+        if (pair.getKey().isAlwaysFalse()) {

Review comment:
       Yes! I am adding the else.




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