content: /*
   * 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.examples;
  
  import org.apache.calcite.plan.RelOptUtil;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.core.JoinRelType;
  import org.apache.calcite.sql.fun.SqlStdOperatorTable;
  import org.apache.calcite.test.RelBuilderTest;
  import org.apache.calcite.tools.FrameworkConfig;
  import org.apache.calcite.tools.RelBuilder;
  
  /**
   * Example that uses {@link org.apache.calcite.tools.RelBuilder}
   * to create various relational expressions.
   */
  public class RelBuilderExample {
    private final boolean verbose;
  
    public RelBuilderExample(boolean verbose) {
      this.verbose = verbose;
    }
  
    public static void main(String[] args) {
      new RelBuilderExample(true).runAllExamples();
    }
  
    public void runAllExamples() {
      // Create a builder. The config contains a schema mapped
      // to the SCOTT database, with tables EMP and DEPT.
      final FrameworkConfig config = RelBuilderTest.config().build();
      final RelBuilder builder = RelBuilder.create(config);
      for (int i = 0; i <= 4; i++) {
        doExample(builder, i);
        final RelNode node = builder.build();
        if (verbose) {
          System.out.println(RelOptUtil.toString(node));
        }
      }
    }
  
    private RelBuilder doExample(RelBuilder builder, int i) {
      switch (i) {
      case 0:
        return example0(builder);
      case 1:
        return example1(builder);
      case 2:
        return example2(builder);
      case 3:
        return example3(builder);
      case 4:
        return example4(builder);
      default:
        throw new AssertionError("unknown example" + i);
      }
    }
  
    /**
     * Creates a relational expression for a values.
     * It is equivalent to
     *
     * <blockquote><pre>VALUES((1, TRUE), (NULL, FALSE))</pre></blockquote>
     */
    private RelBuilder example0(RelBuilder builder) {
      return builder
          .values(new String[] {"a", "b"}, 1, true, null, false);
    }
  
    /**
     * Creates a relational expression for a table scan.
     * It is equivalent to
     *
     * <blockquote><pre>SELECT *
     * FROM emp</pre></blockquote>
     */
    private RelBuilder example1(RelBuilder builder) {
      return builder
          .scan("EMP");
    }
  
    /**
     * Creates a relational expression for a table scan and project.
     * It is equivalent to
     *
     * <blockquote><pre>SELECT deptno, ename
     * FROM emp</pre></blockquote>
     */
    private RelBuilder example2(RelBuilder builder) {
      return builder
          .scan("EMP")
          .project(builder.field("DEPTNO"), builder.field("ENAME"));
    }
  
    /**
     * Creates a relational expression for a table scan, aggregate, filter.
     * It is equivalent to
     *
     * <blockquote><pre>SELECT deptno, count(*) AS c, sum(sal) AS s
     * FROM emp
     * GROUP BY deptno
     * HAVING count(*) &gt; 10</pre></blockquote>
     */
    private RelBuilder example3(RelBuilder builder) {
      return builder
          .scan("EMP")
          .aggregate(builder.groupKey("DEPTNO"),
              builder.count(false, "C"),
              builder.sum(false, "S", builder.field("SAL")))
          .filter(
              builder.call(SqlStdOperatorTable.GREATER_THAN, builder.field("C"),
                  builder.literal(10)));
    }
  
    /**
     * Sometimes the stack becomes so deeply nested it gets confusing. To keep
     * things straight, you can remove expressions from the stack. For example,
     * here we are building a bushy join:
     *
     * <blockquote><pre>
     *                join
     *              /      \
     *         join          join
     *       /      \      /      \
     *     EMP     DEPT  EMP    BONUS
     * </pre></blockquote>
     *
     * <p>We build it in three stages. Store the intermediate results in variables
     * `left` and `right`, and use `push()` to put them back on the stack when it
     * is time to create the final `Join`.
     */
    private RelBuilder example4(RelBuilder builder) {
      final RelNode left = builder
          .scan("EMP")
          .scan("DEPT")
          .join(JoinRelType.INNER, "DEPTNO")
          .build();
  
      final RelNode right = builder
          .scan("EMP")
          .scan("BONUS")
          .join(JoinRelType.INNER, "ENAME")
          .build();
  
      return builder
          .push(left)
          .push(right)
          .join(JoinRelType.INNER, "ENAME");
    }
  }
  