Re: Don't see CLOSE packet been sent

Hi Team,
Writing to ask for a follow up. Can someone please clarify. I only see
CLOSE been sent by driver when server returns an error message 'prepared
statement does not exist".

Thanks
Manav

On Thu, Dec 4, 2025 at 7:07 PM Manav Kumar <mkumar(at)yugabyte(dot)com> wrote:

> Hi Team,
> Wrote a simple below application to understand nature of CLOSE packet.
> But i don't see the JDBC sending CLOSE packet. Any ideas what i can do see
> CLOSE packet.
> I'm compiling with:
> javac -classpath /home/manavkumar/postgresql-42.7.1.jar sendClose.java && \
> java -cp .:/home/manavkumar/postgresql-42.7.1.jar sendClose
>
> ```import java.sql.*;
>
> public class sendClose {
>
> public static void main(String[] args) {
> Connection connection = null;
> PreparedStatement pstmt1 = null, pstmt2 = null;
>
> try {
> // prepareThreshold=1 is crucial here
> connection = DriverManager.getConnection("jdbc:postgresql://
> 10.150.3.175:5433/yugabyte?prepareThreshold=1", "yugabyte","yugabyte");
>
> // ---------------------------------------------------------
> // CHANGE 1: Use placeholders (?)
> // This forces the driver to use Extended Query Protocol (Parse/Bind)
> // and create a named statement (e.g., "S_1") on the server.
> // ---------------------------------------------------------
> pstmt1 = connection.prepareStatement("insert into t_ values (?, ?)");
> pstmt1.setInt(1, 1);
> pstmt1.setInt(2, 2);
> // Execute twice to ensure the driver switches to server-prepare mode
> pstmt1.execute();
> pstmt1.execute();
> pstmt1.execute();
> pstmt1.execute();
> pstmt1.execute();
> pstmt1.execute();
> pstmt1.execute();
> pstmt1.execute();
> pstmt1.execute();
> pstmt1.execute();
> // ---------------------------------------------------------
> // CHANGE 2: Close the statement
> // The driver now marks "S_1" as closed internally and queues the packet.
> // ---------------------------------------------------------
> pstmt1.close();
>
> System.out.println("Statement 1 closed. Sending Statement 2 to flush the
> buffer...");
>
> // ---------------------------------------------------------
> // CHANGE 3: Send ANY other traffic
> // The driver will attach the buffered "CLOSE S_1" packet
> // to the front of this new request.
> // ---------------------------------------------------------
> pstmt2 = connection.prepareStatement("SELECT 1");
> pstmt2.execute();
> pstmt2.close();
>
> connection.close();
> }
> catch (Exception e) {
> e.printStackTrace();
> }
> }
> }
>
> ```
>