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# PostgreSQL pl/pgsql Debugger API
This module is a set of shared libraries which implement an API for debugging
pl/pgsql functions on PostgreSQL 8.4 and above. The
[pgAdmin project](http://www.pgadmin.org/) provides a client user interface.
## Installation
- Copy this directory to contrib/ in your PostgreSQL source tree.
- Run `make && make install`
- Edit your postgresql.conf file, and modify the shared_preload_libraries config
option to look like:
`shared_preload_libraries = '$libdir/plugin_debugger'`
- Restart PostgreSQL for the new setting to take effect.
- Run the following command in the database or databases that you wish to
debug functions in:
`CREATE EXTENSION pldbgapi;`
(on server versions older than 9.1, you must instead run the pldbgapi--1.1.sql
script directly using psql).
## Usage
Connect pgAdmin to the database containing the functions you wish to debug.
Right-click the function to debug, and select Debugging->Debug to execute and
debug the function immediately, or select Debugging->Set Global Breakpoint to
set a breakpoint on the function. This will cause the debugger to wait for
another session (such as a backend servicing a web app) to execute the function
and allow you to debug in-context.
For further information, please see the pgAdmin documentation.
## Troubleshooting
The majority of problems we've encountered with the plugin are caused by
failing to add (or incorrectly adding) the debugger plugin library to the
shared_preload_libraries configuration directive in postgresql.conf (following
which, the server *must* be restarted). This will prevent global breakpoints
working on all platforms, and on some (notably Windows) may prevent the
pldbgapi.sql script from executing correctly.
## Architecture
The debugger consists of three parts:
1. The client. This is typically a GUI displays the source code, current
stack frame, variables etc, and allows the user to set breakpoints and
step throught the code. The client can reside on a different host than
the database server.
2. The target backend. This is the backend that runs the code being debugged.
The plugin_debugger.so library must be loaded into the target backend.
3. Debugging proxy. This is another backend process that the client is
connected to. The API functions, pldbg_* in pldbgapi.so library, are
run in this backend.
The client is to connected to the debugging proxy using a regular libpq
connection. When a debugging session is active, the proxy is connected
to the target via a socket. The protocol between the proxy and the target
backend is not visible to others, and is subject to change. The pldbg_*
API functions form the public interface to the debugging facility.
```
debugger client *------ libpq --------* Proxy backend
(pgAdmin) *
|
pldebugger socket connection
|
*
application client *----- libpq -------* Target backend
```
## Licence
The pl/pgsql debugger API is released under the
[Artistic Licence v2.0](https://opensource.org/licenses/artistic-license-2.0).
Copyright (c) 2004-2024 EnterpriseDB Corporation. All Rights Reserved.
## Contact
For support, please email the pgAdmin support mailing list. See
[http://www.pgadmin.org/support/](http://www.pgadmin.org/support/) for more
details.
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