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/**
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 *  '$RCSfile$'
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 *    Purpose: An adapter class for PostgreSQL RDBMS.
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 *  Copyright: 2000 Regents of the University of California and the
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 *             National Center for Ecological Analysis and Synthesis
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 *    Authors: Jivka Bojilova
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 *    Release: @release@
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 *
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 *   '$Author: tao $'
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 *     '$Date: 2002-05-23 20:38:18 -0700 (Thu, 23 May 2002) $'
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 * '$Revision: 1128 $'
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 *
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 * This program is free software; you can redistribute it and/or modify
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 * it under the terms of the GNU General Public License as published by
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 * the Free Software Foundation; either version 2 of the License, or
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 * (at your option) any later version.
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 *
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 * This program is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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 * GNU General Public License for more details.
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 *
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 * You should have received a copy of the GNU General Public License
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 * along with this program; if not, write to the Free Software
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 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
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 */
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package edu.ucsb.nceas.dbadapter;
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import java.sql.*;
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import edu.ucsb.nceas.metacat.*;
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/**
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 * The PostgreSQL db adapter implementation.
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 */
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public class PostgresqlAdapter extends AbstractDatabase {
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  /**
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   * The PostgreSQL unique ID /sequence generator
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   * The name of the sequence used to generate the unique id 
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   * is made from the name of the table that uses the id by 
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   * appending "_id_seq" to it.
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   * When record is inserted in the table and insert trigger gets
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   * a nextval from that sequence, select currval of that sequence
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   * can return the generated key in the same db connection.
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   *
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   * @param conn db connection in which the unique id was generated
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   * @param tableName the name of table which unique id was generate
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   * @exception SQLException any SQLException that can be thrown 
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   *            during the db operation
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   * @return return the generated unique id as a long type
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   */
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  public long getUniqueID(String tableName) 
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                                         throws SQLException {
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    long uniqueid = 0;
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    DBConnection conn = null;
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    int serialNumber = -1;
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    Statement stmt = null;
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    try
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    {
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      //check out DBConnection
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      conn=DBConnectionPool.getDBConnection("PostgresqlAdapter.getUniqueID");
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      serialNumber=conn.getCheckOutSerialNumber();
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      stmt = conn.createStatement();
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      stmt.execute("SELECT currval('" + tableName + "_id_seq')");
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      ResultSet rs = stmt.getResultSet();
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      if ( rs.next() ) 
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		  {
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        uniqueid = rs.getLong(1);
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      }
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      stmt.close();
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    }//try
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    finally
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    {
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      DBConnectionPool.returnDBConnection(conn, serialNumber);
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    }//finally
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      //System.out.println("Unique ID: " + uniqueid);    
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    return uniqueid;
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  }
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  /**
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   * The PostgreSQL function name that gets the current date 
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   * and time from the database server
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   *
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   * @return return the current date and time function name: "now()"
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   */
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  public String getDateTimeFunction() {
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    //System.out.println("The date and time function: " + "now()");    
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		//to return just the date use now()::date
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		//and for the time use now()::time
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    return "now()";
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  }
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  /**
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   * The PostgreSQL function name that is used to return non-NULL value
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   *
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   * @return return the non-NULL function name: "coalesce"
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   */
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  public String getIsNULLFunction() {
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    return "coalesce";
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  }
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  /**
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   * PostgreSQL's string delimiter character: single quote (')
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   *
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   * @return return the string delimiter: single quote (')
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   */
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  public String getStringDelimiter() {
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    return "\"";
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  }
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}
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