support setting application_name for each session

[neverchanje]

Is your feature request related to a problem? Please describe.

Required by DataGrip.

Upon establishing a session, the client will set application_name in the FeStartupMessage. For psql, the application name is psql. For DataGrip, it is "DataGrip 2023.1.2".

In addition, Postgres allows dynamically setting the variable via set application_name to my_application;. We may also support it in the future.

Describe the solution you'd like

No response

Describe alternatives you've considered

No response

Additional context

No response

[TennyZhuang]

Unfortunately, JDBC will not send application_name if the server version is <= 9.0, see the screenshot.

So the issue was likely blocked by #10099

[TennyZhuang]

A workaround: use assumeMinServerVersion=9.0.0 in the connection string, and wait #10356 to be merged.

[TennyZhuang]

The JDBC behavior

[TennyZhuang]

When #10600 get merged, the only blocker is the version number #10099. I can pass the test with the simple Java program if the version number returned by the server is "9.0.0":

The workaround: add assumeMinServerVersion=9.0.0 to the end of the connection string, then it can directly pass now.

package com.example;

import java.sql.*;
import java.util.Properties;

public class App {
    public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;

        try {
            // Load the PostgreSQL driver class
            Class.forName("org.postgresql.Driver");

            // Create a connection to the dev database on localhost:4566 with username 'root'
            String url = "jdbc:postgresql://localhost:4566/dev?ApplicationName=test111";
            String user = "root";
            String password = "";

            conn = DriverManager.getConnection(url, user, password);

            {
                Properties prop = conn.getClientInfo();
                System.out.println(prop);
            }
            // Create a statement to execute SQL queries
            stmt = conn.createStatement();

            // Execute a SELECT 1 query
            rs = stmt.executeQuery("SELECT 1");

            // Process the results of the query
            while (rs.next()) {
                int result = rs.getInt(1);

                System.out.printf("Result: %d\n", result);
            }
            {
                Properties prop = conn.getClientInfo();
                System.out.println(prop);
            }

        } catch (SQLException ex) {
            ex.printStackTrace();
        } catch (ClassNotFoundException ex) {
            ex.printStackTrace();
        } finally {
            // Close the ResultSet, Statement, and Connection objects to free up resources
            try {
                if (rs != null) {
                    rs.close();
                }
                if (stmt != null) {
                    stmt.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException ex) {
                ex.printStackTrace();
            }
        }
    }
}

[TennyZhuang]

Fixed in latest main, tested.