HELP! how to use dbx on postgresql?

This question may be too simple here, but I really
need help to make dbx working. I configured the
postgresql with --enable-debug option. I created a
database called "testdb", then I started postmaster.
My purpose is to trace the execution step by step and
understand how postgresql is designed. I typed "dbx
psql" to start the dbx, then I entered "run testdb",
the problem is it jumps into postgres mode, not in dbx
mode (see below). I couldn't do any dbx commands. I am
really not familiar with dbx. Can anyone tell me how I
should run the postgres in debug mode? Thanks a lot!!

-----------------------------------------------------
sunny (51) % dbx psql
The major new features of this release relative to 3.2
are:

o The Collector now supports MT applications (see
`help collectormt')
o Runtime checking (RTC) is supported with
fork/exec/attach (see `help
rtc attach' for details)
o RTC has an API for allocators (see `help rtc api')
o New command `regs' to print current value of
registers (see `help regs')
o New command `showblock' to give details about heap
block (see `help showblock')
o Enhanced `pathmap' command (see `help pathmap')
o New dbxenv variable 'language_mode' (see `help
dbxenv' under `language_mode')
o New dbxenv variable 'output_inherited_members' (ee
`help dbxenv' under
`output_inherited_members')
o Two new dbx read-only variables: $helpfile and
$helpfile_html (see `help help')
o New -v (verbose) flag to the `module' and `modules'
commands
(see `help module' and `help modules')
o New +r flag to print and display commands (see `help
print')
o Default value of dbxenv variable `scope_look_aside'
has been changed
to on (see `help dbxenv' under scope_look_aside and
`help scope')
o New `inobject' event for support of `stop inobject
<c++_obj_exp>'
(see `help c++ inobject' and `help event
specification')
o `inclass' event now supports template classes (see
`help c++ inclass' and
`help event specification')
o `stop at <lineno>' now supports C++ template
definitions as well as
C++ inlined functions defined in header files (see
`help event specification'
under `at' event)
o Support for new C++ operators: `const_cast',
`dynamic_cast',
`reinterpret_cast', and `static_cast'
o Support for new C++ `typeid' operator
o An HTML version of the help file is available (see
`help help')

See also `help changes32'
The major new features of 3.2 (SPARCWorks 3.1)
relative to 3.1 are:

o Objective C support (see `help ObjC')
o Fortran 90 support (see `help fortran')
o Runtime checking (RTC) gives information about
memory usage
(see `help check' and `help showmemuse')
o `whereis -a' shows symbolic name of address (see
`help whereis')
o Support for Pascal's `with' statement
o SPARC V8+ support (see `help dbxenv' and `help
registers')
o Better support for stripped binaries
o One-line descriptions of all commands (see `help
commands')
o dbx outputs and accepts the suffixes `U', `L', and
`LL' to denote
unsigned, long, and long long quantities.

See also `help changes31'.
The major new features of 3.1 (SparcWorks 3.0.2)
relative to 3.0.1 are
o Runtime Checking (RTC) now supports multi-threaded
applications.
See `help rtc mt'. (Solaris 2.x)
o `adb' mode (see `help adb' for details)
o Output format control (see `help dbxenv' under
`output_base')
o Array-slicing for C and C++ (see `help
array-slicing')
o Support for Fortran intrinsic functions.
o `print' flags for $[] (see `help ksh expressions')
o Printf-like output format control (see `help
format')
o Support for user-supplied pretty printing
functions (see
`help prettyprint')
o The `runargs' command (see `help runargs')

See also `help changes301'.

To suppress this message, add the following line to
your .dbxrc file:

dbxenv suppress_startup_message 4.0
Reading symbolic information for psql
Reading symbolic information for rtld /usr/lib/ld.so.1
Reading symbolic information for libpq.so.2
Reading symbolic information for librt.so.1
Reading symbolic information for libz.so.1
Reading symbolic information for libresolv.so.2
Reading symbolic information for libgen.so.1
Reading symbolic information for libnsl.so.1
Reading symbolic information for libsocket.so.1
Reading symbolic information for libdl.so.1
Reading symbolic information for libm.so.1
Reading symbolic information for libc.so.1
Reading symbolic information for libaio.so.1
Reading symbolic information for libmp.so.2
Reading symbolic information for libc_psr.so.1
(dbx) run testdb

Running: psql testdb
(process id 14077)
Welcome to psql, the PostgreSQL interactive terminal.

Type: \copyright for distribution terms
\h for help with SQL commands
\? for help on internal slash commands
\g or terminate with semicolon to execute query
\q to quit

testdb=#
testdb=#

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