import java.sql.*;

import org.postgresql.*;
import org.postgresql.largeobject.*;

public class Threads {

	public static void main(String args[]) throws Exception {
		Class.forName("org.postgresql.Driver");
		Connection conn = DriverManager.getConnection("jdbc:postgresql://localhost:5432/jurka","jurka","");
		conn.setAutoCommit(false);


		Runner runners[] = new Runner[10];
		setupBlob(conn, runners.length);

		for (int i=0; i<runners.length; i++) {
			runners[i] = new Runner(conn, i);
			runners[i].start();
		}
	}

	private static void setupBlob(Connection conn, int len) throws Exception {
		Statement stmt = conn.createStatement();
		stmt.execute("CREATE TEMP TABLE tblob (a int, b oid)");

		PreparedStatement pstmt = conn.prepareStatement("INSERT INTO tblob VALUES (?, lo_creat(-1))");
		for (int i=0; i<len; i++) {
			pstmt.setInt(1,i);
			pstmt.executeUpdate();
		}
		pstmt.close();

		byte buf[] = new byte[2048];
		for (int i=0; i<buf.length; i++) {
			buf[i] = (byte)i;
		}

		LargeObjectManager lom = ((PGConnection)conn).getLargeObjectAPI();
		ResultSet rs = stmt.executeQuery("SELECT b FROM tblob");
		while (rs.next()) {
			LargeObject obj = lom.open(rs.getInt(1), LargeObjectManager.WRITE);
			obj.write(buf, 0, buf.length);
			obj.close();
		}

	}
			

}

class Runner extends Thread {
	private Connection conn;
	private int version;

	public Runner(Connection conn, int version) {
		this.conn = conn;
		this.version = version;
	}

	public void run() {
		while(true) {
			try {
				if (version % 4 == 0) {
					// Normal query execution.
					Statement stmt = conn.createStatement();
					ResultSet rs = stmt.executeQuery("SELECT * FROM pg_class");
					while (rs.next()) { }
					rs.close();
					rs = stmt.executeQuery("SELECT * FROM pg_class");
					while (rs.next()) { }
					rs.close();
					stmt.close();
				} else if (version % 4 == 1) {
					// Use a cursor
					Statement stmt = conn.createStatement();
					stmt.setFetchSize(20);
					ResultSet rs = stmt.executeQuery("SELECT * FROM pg_class");
					while (rs.next()) { }
					rs.close();
					rs = stmt.executeQuery("SELECT * FROM pg_class");
					while (rs.next()) { }
					rs.close();
					stmt.close();
				} else if (version % 4 == 2) {
					// Use a prepared statement
					PreparedStatement pstmt = conn.prepareStatement("SELECT * FROM pg_proc where proname = ?");
					((PGStatement)pstmt).setUseServerPrepare(true);
					pstmt.setString(1, "textin");
					ResultSet rs = pstmt.executeQuery();
					while (rs.next()) { }
					rs.close();
					rs = pstmt.executeQuery();
					while (rs.next()) { }
					rs.close();
					pstmt.setString(1, "version");
					rs = pstmt.executeQuery();
					while (rs.next()) { }
					rs.close();
					pstmt.close();
				} else if (version % 4 == 3) {
					// Use a blob
					PreparedStatement pstmt = conn.prepareStatement("SELECT b FROM tblob WHERE a = ?");
					pstmt.setInt(1, version);
					ResultSet rs = pstmt.executeQuery();
					while (rs.next()) {
						Blob b = rs.getBlob(1);
						for (int i=0; i<b.length(); i++) {
							byte dat[] = b.getBytes(i,1);
						}
					}
					rs.close();
					pstmt.close();
				}
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
	}

}