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v1.1

Documentation:v1.1

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Running the COPY FROM STDIN Statement to Import Data

Data Import Using COPY FROM STDIN

Run the COPY FROM STDIN statement to import data to MogDB in either of the following ways:

  • Write data into the MogDB database by typing. For details, see COPY.
  • Import data from a file or database to MogDB through the CopyManager interface driven by JDBC. You can use any parameters in the COPY syntax.

Introduction to the CopyManager Class

CopyManager is an API class provided by the JDBC driver in MogDB. It is used to import data to the MogDB database in batches.

Inheritance Relationship of CopyManager

The CopyManager class is in the org.postgresql.copy package and inherits the java.lang.Object class. The declaration of the class is as follows:

public class CopyManager
extends Object

Construction Method

public CopyManager(BaseConnection connection)

throws SQLException

Common Methods

Table 1 Common methods of CopyManager

Return Value Method Description throws
CopyIn copyIn(String sql) - SQLException
long copyIn(String sql, InputStream from) Uses COPY FROM STDIN to quickly import data to tables in a database from InputStream. SQLException,IOException
long copyIn(String sql, InputStream from, int bufferSize) Uses COPY FROM STDIN to quickly import data to tables in a database from InputStream. SQLException,IOException
long copyIn(String sql, Reader from) Uses COPY FROM STDIN to quickly import data to tables in a database from Reader. SQLException,IOException
long copyIn(String sql, Reader from, int bufferSize) Uses COPY FROM STDIN to quickly import data to tables in a database from Reader. SQLException,IOException
CopyOut copyOut(String sql) - SQLException
long copyOut(String sql, OutputStream to) Sends the result set of COPY TO STDOUT from the database to the OutputStream class. SQLException,IOException
long copyOut(String sql, Writer to) Sends the result set of COPY TO STDOUT from the database to the Writer class. SQLException,IOException

Example 1: Importing and Exporting Data Through Local Files

When the JAVA language is used for secondary development based on MogDB, you can use the CopyManager interface to export data from the database to a local file or import a local file to the database by streaming. The file can be in CSV or TEXT format.

The sample program is as follows. Load the MogDB JDBC driver before executing it.

import java.sql.Connection;
import java.sql.DriverManager;
import java.io.IOException;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.sql.SQLException;
import org.postgresql.copy.CopyManager;
import org.postgresql.core.BaseConnection;

public class Copy{

     public static void main(String[] args)
     {
      String urls = new String("jdbc:postgresql://localhost:8000/postgres"); // URL of the database
      String username = new String("username");            // Username
      String password = new String("passwd");             // Password
      String tablename = new String("migration_table"); // Table information
      String tablename1 = new String("migration_table_1"); // Table information
      String driver = "org.postgresql.Driver";
      Connection conn = null;

      try {
          Class.forName(driver);
          conn = DriverManager.getConnection(urls, username, password);
      } catch (ClassNotFoundException e) {
           e.printStackTrace(System.out);
      } catch (SQLException e) {
           e.printStackTrace(System.out);
      }

      // Export data from the migration_table table to the d:/data.txt file.
      try {
          copyToFile(conn, "d:/data.txt", "(SELECT * FROM migration_table)");
      } catch (SQLException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
      } catch (IOException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
      }
      // Import data from the d:/data.txt file to the migration_table_1 table.
      try {
          copyFromFile(conn, "d:/data.txt", tablename1);
      } catch (SQLException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
      } catch (IOException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
      }

      // Export data from the migration_table_1 table to the d:/data1.txt file.
      try {
          copyToFile(conn, "d:/data1.txt", tablename1);
      } catch (SQLException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
      } catch (IOException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
      }
  }

  public static void copyFromFile(Connection connection, String filePath, String tableName)
         throws SQLException, IOException {

     FileInputStream fileInputStream = null;

     try {
         CopyManager copyManager = new CopyManager((BaseConnection)connection);
         fileInputStream = new FileInputStream(filePath);
         copyManager.copyIn("COPY " + tableName + " FROM STDIN with (" + "DELIMITER"+"'"+ delimiter +  "'" + "ENCODING " + "'" + encoding + "')", fileInputStream);
     } finally {
         if (fileInputStream != null) {
             try {
                 fileInputStream.close();
             } catch (IOException e) {
                 e.printStackTrace();
             }
         }
     }
 }
     public static void copyToFile(Connection connection, String filePath, String tableOrQuery)
          throws SQLException, IOException {

      FileOutputStream fileOutputStream = null;

      try {
          CopyManager copyManager = new CopyManager((BaseConnection)connection);
          fileOutputStream = new FileOutputStream(filePath);
          copyManager.copyOut("COPY " + tableOrQuery + " TO STDOUT", fileOutputStream);
      } finally {
          if (fileOutputStream != null) {
              try {
                  fileOutputStream.close();
              } catch (IOException e) {
                  e.printStackTrace();
              }
          }
      }
  }
}

Example 2: Migrating Data from a MySQL Database to the MogDB Database

The following example shows how to use CopyManager to migrate data from MySQL to the MogDB database.

import java.io.StringReader;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import org.postgresql.copy.CopyManager;
import org.postgresql.core.BaseConnection;

public class Migration{

    public static void main(String[] args) {
        String url = new String("jdbc:postgresql://localhost:8000/postgres"); // URL of the database
        String user = new String("username");            // MogDB database user name
        String pass = new String("passwd");             // MogDB database password
        String tablename = new String("migration_table_1"); // Table information
        String delimiter = new String("|");              // Delimiter
        String encoding = new String("UTF8");            // Character set
        String driver = "org.postgresql.Driver";
        StringBuffer buffer = new StringBuffer();       // Buffer to store formatted data

        try {
            // Obtain the query result set of the source database.
            ResultSet rs = getDataSet();

            // Traverse the result set and obtain records row by row.
            // The values of columns in each record are separated by the specified delimiter and end with a linefeed, forming strings.
            // Add the strings to the buffer.
            while (rs.next()) {
                buffer.append(rs.getString(1) + delimiter
                        + rs.getString(2) + delimiter
                        + rs.getString(3) + delimiter
                        + rs.getString(4)
                        + "\n");
            }
            rs.close();

            try {
                // Connect to the target database.
                Class.forName(driver);
                Connection conn = DriverManager.getConnection(url, user, pass);
                BaseConnection baseConn = (BaseConnection) conn;
                baseConn.setAutoCommit(false);

                // Initialize the table.
                String sql = "Copy " + tablename + " from STDIN with (DELIMITER " + "'" + delimiter + "'" +","+ " ENCODING " + "'" + encoding + "'");

                // Commit data in the buffer.
                CopyManager cp = new CopyManager(baseConn);
                StringReader reader = new StringReader(buffer.toString());
                cp.copyIn(sql, reader);
                baseConn.commit();
                reader.close();
                baseConn.close();
            } catch (ClassNotFoundException e) {
                e.printStackTrace(System.out);
            } catch (SQLException e) {
                e.printStackTrace(System.out);
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    //********************************
    // Return the query result set from the source database.
    //*********************************
    private static ResultSet getDataSet() {
        ResultSet rs = null;
        try {
            Class.forName("com.MY.jdbc.Driver").newInstance();
            Connection conn = DriverManager.getConnection("jdbc:MY://10.119.179.227:3306/jack?useSSL=false&allowPublicKeyRetrieval=true", "jack", "Gauss@123");
            Statement stmt = conn.createStatement();
            rs = stmt.executeQuery("select * from migration_table");
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return rs;
    }
}
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