Re: Memroy leak with jdbc

Joseph,

The reason this is happening is because this particular select statement
is generating a warning message from the server. If you turn on logging
in the driver (add ?loglevel=2 to the jdbc URL) you will see the
following warning generated for each execution of this sql statement:

NOTICE: Adding missing FROM-clause entry in subquery for table "taba"

These warning messages are stored up until you read them, or call
clearWarnings().

This is all correct behavior AFAICT.

thanks,
--Barry

Joseph Shraibman wrote:
> Using this test case with 9000 interations I get this output:
>
> used: 474,296 free: 1,557,320 total: 2,031,616 max: 67,108,864
> ....................................................................................................
>
> used: 4,646,760 free: 3,643,544 total: 8,290,304 max: 67,108,864
> =================
> used: 4,607,728 free: 3,682,576 total: 8,290,304 max: 67,108,864
>
> I have no idea why this memory leak is happening. It only happens with
> this one select statement, not all select statements.
>
>
> /**
> * PostgresMemTest.java
> *
> *
> * Created: Mon May 5 18:40:29 2003
> *
> * @author <a href="mailto:jks(at)selectacast(dot)net">Joseph Shraibman</a>
> * @version 1.0
> */
> import java.sql.*;
> public class PostgresMemTest {
>
> transient protected Connection db;
>
> public PostgresMemTest(String url,String usr,String pwd) throws
> Exception{
>
> // try {
> // Load the driver
> Class.forName("org.postgresql.Driver");
> // } catch (ClassNotFoundException e){
> // e.printStackTrace();
> //return;
> //}
> // try{
> db = DriverManager.getConnection(url, usr, pwd);
> // } catch (SQLException e){
> //e.printStackTrace();
> //return;
> // }
> Statement st = null;
> st = db.createStatement();
> st.executeUpdate("BEGIN;");
> st.executeUpdate("create temp table taba(pkey int, puindex
> int);");
> st.executeUpdate("create temp table tabpu(pukey int, ukey
> int, pu text);");
> st.executeUpdate("create temp table tabu(ukey int, akey
> int);");
> st.executeUpdate("insert into taba values(1,2);");
> st.executeUpdate("insert into tabu values(3,1);");
> st.executeUpdate("insert into tabpu values(2,3,'blah');");
>
> } // PostgresMemTest constructor
> void doQuery() throws Exception{
> String line = null;
> //None of these remmed out lines produce the memory leak
> //line = "SELECT 'blah'";
> //line = "SELECT (SELECT 'blah');";
> //line = "select pu from tabpu where pukey = 2 and ukey = 3";
> line = "select (select pu from tabpu where pukey = taba.puindex
> and ukey = tabu.ukey) from tabu where ukey = 3 and akey = 1;";
> Statement st = null;
> st = db.createStatement();
> ResultSet rs = st.executeQuery(line);
>
> }
> private static String uft(){
> Runtime rt = Runtime.getRuntime();
> long free = rt.freeMemory(), total = rt.totalMemory(), used =
> total - free;
> long max = rt.maxMemory();
> long max2 = max - 67108864;
>
> java.text.NumberFormat nf = java.text.NumberFormat.getInstance() ;
> return "used: "+nf.format(used)+" free: "+nf.format(free)+
> " total: "+nf.format(total)+" max: "+nf.format(max2);
> }
> //Usage java PostgresMemTest <iterations> <url> <username> <passwd>
> public static void main(String args[])throws Exception{
> PostgresMemTest pmt = new PostgresMemTest(args[1],args[2],args[3]);
> System.out.println(uft());
> int times = Integer.parseInt(args[0]);
> final int perc = times/100;
> for(int i = 0; i < times; i++){
> pmt.doQuery();
> if (i % perc == 0){
> System.out.print('.');
> System.out.flush();
> }
> }
> System.out.println();
> System.out.println(uft());
> System.gc();
> System.gc();
> System.gc();
> System.out.println("=================");
> System.out.println(uft());
>
> }
> } // PostgresMemTest
>
>
>
>