GDB Debugging session PostgreSQL & AGE

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GDB Debugging session PostgreSQL & AGE

Mohamed Mokhtar's photo
Mohamed Mokhtar

Prerequisite

  • Having a running instance of Postgresql server and (having it surely installed beside AGE and debug flag is enabled)

The following commands are used for loading AGE

CREATE EXTENSION age;
LOAD ‘age’;
SET search_path = ag_catalog, "$user", public;

STEPS

  • Open a psql session on a terminal
# create a test db if not having one
/usr/local/pgsql/bin/createdb test
# open psql
/usr/local/pgsql/bin/psql test
  • Open a new tab for having gdb there
sudo gdb
  • Get the backend process's pid
SELECT pg_backend_pid();

  • assume output is 666

  • Attach gdb to that process id

(gdb) attach 666
  • Create break line at some where
(gdb) break src/backend/tcop/postgres.c:4483
  • Execute a query at the backend session
select * from t where id > 1 and id < 10;
  • Trace at the GDB (press n)

Quick guide to GDB

  • To attach to a process: sudo gdb -p

  • Attach breakpoint: break :

  • Run until breakpoint: c

  • Single step into the function: s

  • Step over the function: n

  • Print a value: p or p *

  • Call a function: call

  • Print postgres node: call pprint()

  • Pressing enter key repeats last command.

  • Include directory (source code): dir

References & Resources

gdbapachePostgreSQLSQLDatabases