Message-ID: <gh-pgjdbc-pgjdbc-3993@github.com>
From: "qinarmy-zoro (@qinarmy-zoro)" <noreply+qinarmy-zoro@github.com>
To: "pgjdbc/pgjdbc" <noreply+pgjdbc-pgjdbc@github.com>
Date: Mon, 23 Mar 2026 10:19:27 +0000
Subject: [pgjdbc/pgjdbc] issue #3993: fix Enable cursor-based bug, when start transaction by 'START TRANSAC'
List-Id: <gh-pgjdbc-pgjdbc.github.com>
X-GitHub-Author-Id: 12522817
X-GitHub-Author-Login: qinarmy-zoro
X-GitHub-Issue: 3993
X-GitHub-Repo: pgjdbc/pgjdbc
X-GitHub-State: closed
X-GitHub-Type: issue
X-GitHub-Url: https://github.com/pgjdbc/pgjdbc/issues/3993
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Please read https://stackoverflow.com/help/minimal-reproducible-example 

**Describe the issue**
A clear and concise description of what the issue is.

**Driver Version?** 
42.7.10

**Java Version?**
all
**OS Version?**
all 
**PostgreSQL Version?**
18.3
**To Reproduce**
Steps to reproduce the behaviour:
I reproduce , see https://github.com/PillArmy/army/blob/master/army-example/src/test/java/io/army/temp/PostgreBugReproduce.java

**Expected behaviour**
A clear and concise description of what you expected to happen.
And what actually happens
// org.postgresql.jdbc.PgStatement.executeInternal()
   // no ->  flags |= QueryExecutor.QUERY_FORWARD_CURSOR;

**Logs**
If possible PostgreSQL logs surrounding the occurrence of the issue
Additionally logs from the driver can be obtained adding

Using the following template code make sure the bug can be replicated in the driver alone.
```
package io.army.temp;


import com.alibaba.druid.pool.DruidDataSource;
import org.testng.annotations.Test;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.Properties;

public class PostgreBugReproduce {


    @Test
    public void reproduce() throws Exception {
        try (DruidDataSource db = createDataSource()) {
            try (Connection conn = db.getConnection()) {
                try (Statement stmt = conn.createStatement()) {
                    stmt.executeUpdate(ddl());
                    stmt.executeUpdate("START TRANSACTION READ ONLY");
                    System.out.printf("autoCommit is %s after start transaction%n", conn.getAutoCommit());

                    stmt.setFetchSize(1);
                    // org.postgresql.jdbc.PgStatement.executeInternal()
                    // no ->  flags |= QueryExecutor.QUERY_FORWARD_CURSOR;
                    try (ResultSet rs = stmt.executeQuery("SELECT u.id,u.name FROM u_user as u ORDER BY u.id")) {
                        while (rs.next()) {
                            System.out.printf("id:%s ; name : %s%n", rs.getLong(1), rs.getString(2));
                        }
                    }
                }

            }
        }

    }


    private static String ddl() {
        return """
                create table IF NOT EXISTS u_user
                (
                    id                 BIGSERIAL       not null primary key,
                    name varchar(15)  not null 
                );
                
                """;
    }


    private static DruidDataSource createDataSource() {

        final String url;
        url = "jdbc:postgresql://localhost:5432/postgres";

        final Properties properties = new Properties();
        properties.put("user", "army_w");
        properties.put("password", "army123");

        final DruidDataSource ds;
        ds = new DruidDataSource();

        ds.setUrl(url);
        ds.setDriverClassName(org.postgresql.Driver.class.getName());
        ds.setConnectProperties(properties);

        ds.setInitialSize(10);
        ds.setMaxActive(200);
        ds.setMaxWait(27L * 1000L);
        ds.setValidationQuery("SELECT 1 ");

        ds.setTestOnBorrow(Boolean.FALSE);
        ds.setTestWhileIdle(Boolean.TRUE);
        ds.setTestOnReturn(Boolean.TRUE);
        ds.setTimeBetweenEvictionRunsMillis(5L * 1000L);

        ds.setRemoveAbandoned(Boolean.FALSE);
        ds.setMinEvictableIdleTimeMillis(30000L);
        return ds;
    }

}

```