place to compile, debug, and mangle postgres

Mangler is built and deployed using Docker

1. Build Mangler

   docker build -t postgres_debug .

2. Run Mangler

   docker run -it --rm postgres_debug bash

1. Create a new postgres database cluster

   initdb -D /usr/local/pgsql/data

2. Start the database server

   pg_ctl -D /usr/local/pgsql/data -l logfile start

3. Create a test database

   createdb my_test_db

4. Connect to the new database

   psql my_test_db

5. Create a new table

   create table author(
       id serial primary key,
       name varchar(200)
   );
   

6. Create some test data

   insert into author (name) values ('Daniel Silva');
   insert into author (name) values ('Tom Clancy');
   

7. Quit the postgres connection

   \q

8. Go to another terminal tab, exec to the existing container, and start a postgres connection

   psql my_test_db

9. Get the process id for this connection

   select pg_backend_pid();

10. Go back to the original window and start a debugging session and attach this process id (example using process id 100)

    gdb attach -p 100

11. Set a breakpoint at the beginning of executing a sql statement

    exec_simple_query

    Shows output:

    Breakpoint 1 at 0x6e1db9: file postgres.c, line 885.

12. Go back to the second terminal and issue a select statement - it shouldn't return because it should hit the breakpoint

    select name from author where id = 1;

13. Go back to the original terminal and enjoy debugging!