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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-3243) (jdbc net client) exception during normal iteration through "ResultSet" of "select * from t"
Date Mon, 28 Jan 2008 12:49:35 GMT

    [ https://issues.apache.org/jira/browse/DERBY-3243?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12563132#action_12563132
] 

Knut Anders Hatlen commented on DERBY-3243:
-------------------------------------------

Does the DRDA spec require that locators are two-byte integers, or could we use four bytes?
Seems like we at least should make EmbedConnection.lobHMKey wrap around on the max value we
are able to send over DRDA, and ensure that it doesn't go negative.

I don't think resetting the lob key on commit/rollback works, as the client does not expect
the keys to be reused. Old Clob/Blob objects on the client will then start returning data
for the queries performed in the new transaction. I ran the code below to test it.

-----8<-----
import java.sql.*;

public class ResetCounter {
    public static void main(String[] args) throws Exception {
        Class.forName("org.apache.derby.jdbc.ClientDriver");
        Connection c = DriverManager.getConnection(
            "jdbc:derby://localhost/db;create=true");

        Statement s1 = c.createStatement();
        ResultSet rs1 = s1.executeQuery("values cast('first' as clob)");
        rs1.next();
        Clob first = rs1.getClob(1);
        rs1.close(); // auto-commit happens here

        Statement s2 = c.createStatement();
        ResultSet rs2 = s2.executeQuery("values cast('second' as clob)");
        rs2.next();
        Clob second = rs2.getClob(1);

        System.out.println("1: " + first.getSubString(1, 100)); // should fail
        System.out.println("2: " + second.getSubString(1, 100));

        rs2.close();
    }
}
----->8-----

Without the patch, first.getSubString(1, 100) failed (correctly) because the transaction in
which the Clob was created, had been committed. With the patch applied, it instead returned
the data that the second transaction had retrieved.

> (jdbc net client) exception during normal iteration through "ResultSet" of "select *
from t"
> --------------------------------------------------------------------------------------------
>
>                 Key: DERBY-3243
>                 URL: https://issues.apache.org/jira/browse/DERBY-3243
>             Project: Derby
>          Issue Type: Bug
>          Components: JDBC
>    Affects Versions: 10.3.2.1
>         Environment: ------------------ Java Information ------------------
> Java Version:    1.4.2_03
> Java Vendor:     Sun Microsystems Inc.
> Java home:       C:\Programme\Java\j2re1.4.2_03
> Java classpath:  derbyclient.jar
> OS name:         Windows XP
> OS architecture: x86
> OS version:      5.1
> Java user name:  cbdqok
> Java user home:  C:\Dokumente und Einstellungen\cbdqok
> Java user dir:   D:\users\cbdqok\privat\osj\lib_derby_net\lib
> java.specification.name: Java Platform API Specification
> java.specification.version: 1.4
> --------- Derby Information --------
> JRE - JDBC: J2SE 1.4.2 - JDBC 3.0
> [D:\users\cbdqok\privat\osj\lib_derby_net\lib\derbyclient.jar] 10.3.1.4 - (561794)
> ------------------------------------------------------
> ----------------- Locale Information -----------------
> ------------------------------------------------------
>            Reporter: Oliver Seidel
>            Priority: Critical
>         Attachments: derby-3243_fix_double_hashmap_entry_diff.txt, derby-3243_fix_double_hashmap_entry_stat.txt
>
>
> Thanks again to the DERBY developers.
> For my convenience I use the client/server variant of DERBY.  This is where the error
occurs.  I have temporarily alleviated the problem for my case by using the embedded version.
> I'm forced to use outlook and have built a program which siphons the messages into a
derby database (phase 1 -- table has two varchar fields and a clob).  When reading them back
(phase 2 -- simple select of all records in no particular order, all 3 attributes), it has
developed an exception.  This is a result of data volume.  I have reduced the problem to a
single demonstration program.
> This behaviour, and the fact that the error is not a "DERBY Exception", but a proper
exception coming back from the JDBC call, leads me to the diagnosis that it is a derby network
client jdbc problem.
> The problem has been reproduced once by Bryan Pendleton: http://www.nabble.com/IndexOutOfBoundsException-t4926228.html
> I'll try to attach the code "error.java"; it can also be found on: http://www.os10000.net/error.java
> Please use as follows:
> javac -classpath derby.jar:derbynet.jar error.java
> java -cp .:derby.jar:derbynet.jar error
> It will create a directory "test_db" and fill it with approx 120mb data.
> Then you will observe the failure. 
> /* -*- Mode:Java; c-basic-offset:8 -*- */
> // --------------------------------------------------------------------------------
> public class error {
> 	// ------------------------------------------------------------------------
> 	public static final int port = 1527;
> 	public static final String host = "127.0.0.1";
> 	// ------------------------------------------------------------------------
> 	public static void log(String x) { System.out.println(x); };
> 	// ------------------------------------------------------------------------
> 	public static void log_stacktrace(Exception e) {
>                 java.io.StringWriter sw = new java.io.StringWriter();
>                 java.io.PrintWriter pw = new java.io.PrintWriter(sw);
>                 e.printStackTrace(pw);
>                 log(sw.toString());
> 	};
> 	// ------------------------------------------------------------------------
> 	public static void start_server() {
> 		try {
> 			org.apache.derby.drda.NetworkServerControl server =
> 				new org.apache.derby.drda.NetworkServerControl(java.net.InetAddress.getByName(host),port);
> 			server.start(null);
> 			try { java.lang.Thread.sleep(5000); } catch (Exception e) { };
> 			log("started DERBY on host "+host+" port "+Integer.toString(port)+".");
> 		} catch (Exception e) {
> 			log_stacktrace(e);
> 		};
> 	};
> 	// ------------------------------------------------------------------------
> 	public static java.sql.Connection con()
> 		throws java.sql.SQLException, java.lang.ClassNotFoundException {
> 		Class.forName("org.apache.derby.jdbc.ClientDriver");
> 		String x_dbse = "test_db";
> 		String x_user = ";user=os10000";
> 		String x_pass = ";password=ding";
> 		String x_crte = ";create=true";
> 		String x_msgs = ";retrieveMessagesFromServerOnGetMessage=true";
> 		String connect = "jdbc:derby://"+host+":"+port+"/"+x_dbse+x_user+x_crte+x_msgs;
> 		return java.sql.DriverManager.getConnection(connect);
> 	};
> 	// ----------------------------------------------------------------------
> 	public static String getclob(java.sql.Clob b) {
> 		java.io.CharArrayWriter caw = new java.io.CharArrayWriter();
> 		try {
> 			java.io.Reader rd = b.getCharacterStream();
> 			char cb[] = new char[4096];
> 			int off=0, bts = rd.read(cb);
> 			while (bts>0) { caw.write(cb,off,bts); off+=bts; bts=rd.read(cb); };
> 			rd.close();
> 		} catch(Exception e) {};
> 		String res = caw.toString();
> 		caw.close();
> 		return res;
> 	};
> 	// ----------------------------------------------------------------------
> 	public static class myclob implements java.sql.Clob {
> 		String v;
> 		public myclob(String z) { v=z; };
> 		public java.io.InputStream getAsciiStream() { return new java.io.ByteArrayInputStream(v.getBytes());
};
> 		public java.io.Reader getCharacterStream() { return new java.io.CharArrayReader(v.toCharArray());
};
> 		public String getSubString(long pos, int length) { return v.substring((int)pos,(int)(pos+length));
};
> 		public long length() { return v.length(); };
> 		public long position(java.sql.Clob pattern, long start) { return 0; };
> 	        public long position(String pattern, long start) { return 0; };
> 		public java.io.OutputStream setAsciiStream(long pos) {
> 			new java.sql.SQLException("setAsciiStream not implemented."); return null; };
> 		public java.io.Writer setCharacterStream(long pos) {
> 			new java.sql.SQLException("setCharacterStream not implemented."); return null; };
> 		public int setString(long pos, String s) {
> 			new java.sql.SQLException("setString not implemented."); return -1; };
> 		public int setString(long pos, String s, int offset, int len) {
> 			new java.sql.SQLException("setString not implemented."); return -1; };
> 		public void truncate(long len) {
> 			new java.sql.SQLException("truncate not implemented."); };
> 	};
> 	public static java.sql.Clob putclob(String x) { return new myclob(x); };
> 	
> 	// ------------------------------------------------------------------------
> 	public static String getLob(java.sql.ResultSet rs, int arg)
> 		throws java.sql.SQLException { return getclob(rs.getClob(arg)); };
> 	public static void setLob(java.sql.PreparedStatement ps, int arg, String val)
> 		throws java.sql.SQLException { ps.setClob(arg,putclob(val)); };
> 	// ------------------------------------------------------------------------
> 	public static String clean_string(String x) {
> 		return x.replaceAll("[\0\r\\\\]","").replaceAll("'","\\\"").replaceAll(",+",",");
> 	};
> 	// ------------------------------------------------------------------------
> 	public static String make_string(int digits) {
> 		double dl = (Math.random()) * (Math.pow(10.0,digits*Math.random()));
> 		int len = (int) dl;
> 		byte buf[] = new byte[len];
> 		while (len>0) {
> 			double db = 256*Math.random();
> 			buf[--len] = (byte)db;
> 		};
> 		return clean_string(new String(buf));
> 	};
> 	// ------------------------------------------------------------------------
> 	public static void update(java.sql.Connection c, String cmd)
> 		throws java.sql.SQLException {
> 		c.createStatement().execute(cmd);
> 	};
> 	// ------------------------------------------------------------------------
> 	public static final int entries=100000;
> 	public static void fill_db(java.sql.Connection c)
> 		throws java.sql.SQLException {
> 		try { update(c,"drop table mail_raw"); } catch (Exception e) {};
> 		try { update(c,"create table mail_raw ( msg varchar(999), att varchar(100), val clob
)"); } 
> 		catch (Exception e) { log_stacktrace(e); };
> 		java.sql.PreparedStatement pstmt = null;
> 		try { pstmt = c.prepareStatement("insert into mail_raw values ( ?, ?, ? )"); }
> 		catch (Exception e) { log_stacktrace(e); };
> 		for (int i=0; i<entries; i++) {
> 			pstmt.setString(1,make_string(3));
> 			pstmt.setString(2,"5 body");
> 			setLob(pstmt,3,make_string(4));
> 			pstmt.executeUpdate();
> 			if (i%100==0) log("step "+i+"/"+entries);
> 		};
> 	};
> 	// ------------------------------------------------------------------------
> 	public static void dump_db(java.sql.Connection c)
> 		throws java.sql.SQLException {
> 		log("performing dump.");
> 		java.sql.ResultSet rs = c.createStatement().executeQuery("select * from mail_raw");
> 		while (rs.next()) {
> 			String msg = rs.getString(1);
> 			String att = rs.getString(2);
> 			String val = getLob(rs,3);
> 		};
> 	};
> 	// ------------------------------------------------------------------------
> 	public static void main(String args[]) {
> 		start_server();
> 		try {
> 			java.sql.Connection c = con();
> 			fill_db(c);
> 			dump_db(c);
> 		} catch (Exception e) { log_stacktrace(e); };
> 	};
> 	// ------------------------------------------------------------------------
> };

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