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.arrow.adapter.jdbc.h2;
  
  import static org.apache.arrow.adapter.jdbc.AbstractJdbcToArrowTest.sqlToArrow;
  import static org.junit.jupiter.api.Assertions.assertEquals;
  
  import java.sql.Connection;
  import java.sql.DriverManager;
  import java.sql.PreparedStatement;
  import java.sql.ResultSet;
  import java.sql.ResultSetMetaData;
  import java.sql.SQLException;
  import java.sql.Statement;
  import java.util.List;
  import org.apache.arrow.memory.RootAllocator;
  import org.apache.arrow.vector.VectorSchemaRoot;
  import org.apache.arrow.vector.types.pojo.Field;
  import org.apache.arrow.vector.types.pojo.Schema;
  import org.junit.jupiter.api.AfterEach;
  import org.junit.jupiter.api.BeforeEach;
  import org.junit.jupiter.api.Test;
  
  public class JdbcAliasToArrowTest {
    private Connection conn = null;
  
    private static final String CREATE_STATEMENT = "CREATE TABLE example_table (id INTEGER);";
    private static final String INSERT_STATEMENT = "INSERT INTO example_table (id) VALUES (?);";
    private static final String QUERY = "SELECT id as a, id as b FROM example_table;";
    private static final String DROP_STATEMENT = "DROP TABLE example_table;";
    private static final String ORIGINAL_COLUMN_NAME = "ID";
    private static final String COLUMN_A = "A";
    private static final String COLUMN_B = "B";
  
    @BeforeEach
    public void setUp() throws Exception {
      String url = "jdbc:h2:mem:JdbcAliasToArrowTest";
      String driver = "org.h2.Driver";
      Class.forName(driver);
      conn = DriverManager.getConnection(url);
      try (Statement stmt = conn.createStatement()) {
        stmt.executeUpdate(CREATE_STATEMENT);
      }
    }
  
    /**
     * Test h2 database query with alias for column name and column label. To verify reading field
     * alias from an H2 database works as expected. If this test fails, something is either wrong with
     * the setup, or the H2 SQL behavior changed.
     */
    @Test
    public void testReadH2Alias() throws Exception {
      // insert rows
      int rowCount = 4;
      insertRows(rowCount);
  
      try (ResultSet resultSet = conn.createStatement().executeQuery(QUERY)) {
        ResultSetMetaData rsmd = resultSet.getMetaData();
        assertEquals(2, rsmd.getColumnCount());
  
        // check column name and column label
        assertEquals(ORIGINAL_COLUMN_NAME, rsmd.getColumnName(1));
        assertEquals(COLUMN_A, rsmd.getColumnLabel(1));
        assertEquals(ORIGINAL_COLUMN_NAME, rsmd.getColumnName(2));
        assertEquals(COLUMN_B, rsmd.getColumnLabel(2));
  
        int rowNum = 0;
  
        while (resultSet.next()) {
          assertEquals(rowNum, resultSet.getInt(COLUMN_A));
          assertEquals(rowNum, resultSet.getInt(COLUMN_B));
          ++rowNum;
        }
  
        assertEquals(rowCount, rowNum);
      }
    }
  
    /**
     * Test jdbc query results with alias to arrow works expected. Arrow result schema name should be
     * field alias name.
     */
    @Test
    public void testJdbcAliasToArrow() throws Exception {
      int rowCount = 4;
      insertRows(rowCount);
  
      try (ResultSet resultSet = conn.createStatement().executeQuery(QUERY)) {
        final VectorSchemaRoot vector = sqlToArrow(resultSet, new RootAllocator(Integer.MAX_VALUE));
  
        assertEquals(rowCount, vector.getRowCount());
        Schema vectorSchema = vector.getSchema();
        List<Field> vectorFields = vectorSchema.getFields();
        assertEquals(COLUMN_A, vectorFields.get(0).getName());
        assertEquals(COLUMN_B, vectorFields.get(1).getName());
      }
    }
  
    @AfterEach
    public void tearDown() throws SQLException {
      try (Statement stmt = conn.createStatement()) {
        stmt.executeUpdate(DROP_STATEMENT);
      } finally {
        if (conn != null) {
          conn.close();
          conn = null;
        }
      }
    }
  
    private void insertRows(int numRows) throws SQLException {
      // Insert [numRows] Rows
      try (PreparedStatement stmt = conn.prepareStatement(INSERT_STATEMENT)) {
        for (int i = 0; i < numRows; ++i) {
          stmt.setInt(1, i);
          stmt.executeUpdate();
        }
      }
    }
  }
  