SET SESSION variable has not effect (3 replies)

Hi,

I am currently working on a java client using jdbc to insert important amount of data into a mysql table.

My choice is to insert multiple rows at once using multiple-insert syntax : "INSERT INTO table (a,b) VALUES (1,2),(3,4),(5,6)..."

Thus I append to submit to mysql big insert statement which size exceeds mysql's default max_allowed_packet value (which is 1M).

So I tried to modify this value on session-scope basis, before submiting my big insert. But it seems it just has not effect, and the query is still refused by mysql.

Here is my java code :

--------------------------------------------------------------------
// increase max_allowed_packet to 8M
Statement stmtSet = connection.createStatement();
stmtSet.execute("SET SESSION max_allowed_packet = 8 * 1024 * 1024;");

// check if value was changed
Statement stmtShow = connection.createStatement();
ResultSet rs = stmtShow.executeQuery("SHOW SESSION VARIABLES like 'max_allowed_packet'");
rs.next();
System.out.println(rs.getString(1)+"="+rs.getString(2));

// try to execute the big insert
Statement stmtInsert = connection.createStatement();
stmtInsert.executeUpdate(bigInsert));
------------------------------------------------------------------


And what this code prints :
-----------------------------------------------------------
max_allowed_packet=8388608
com.mysql.jdbc.PacketTooBigException: Packet for query is too large (4796533 > 1048576). You can change this value on the server by setting the max_allowed_packet' variable.
at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:2655)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1604)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1715)
at com.mysql.jdbc.Connection.execSQL(Connection.java:3243)
at com.mysql.jdbc.Statement.executeUpdate(Statement.java:1343)
at com.mysql.jdbc.Statement.executeUpdate(Statement.java:1260)
-------------------------------------------------------------------


As you can see the max_allowed_packet has indeed been changed to 8M value but I still get PacketTooBigException, although my insert query is only 4M long.

I also add that every statements are executed within the same session.

If someone has an idea of what's happening, I would appreciate a lot.

Thanks !