Re: Don't see CLOSE packet been sent - Mailing list pgsql-jdbc

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@yugabyte.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();

}

}

}

```