Re: Memroy leak with jdbc - Mailing list pgsql-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@selectacast.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
>
>
>
>