PostgreSQL internals development with VSCode

In my brief stint with Hive (which resulted in this and this blog), I used IntelliJ IDEA. I was reintroduced to the marvels of IDEs and how easy they make a developer's life. I had used Visual Studio, TurboC and many other language specific IDEs back in my college days. But once I started working exclusively with C and Linux, I was confined to vim, gdb, cgdb and at the most ddd. (Didn't use emacs. But I hear that's cool IDE as well.) I had kinda forgot what comfort it is to work in an IDE. These tools are certainly great and if one spends enough time, they can be better than any of the IDEs out there. But there's a sharp learning curve there. So, I was reminded of that comfort and sorely missed a good IDE when I started working with PostgreSQL again. But by then VSCode was made available on Linux. It's not as fantastic as IntelliJ or GoLand but it's good enough to improve a C developer's life; not to mention efficiency.

I like a. ability to edit, browse and debug code simultaneously, b. all the contextual language specific auto-suggestions c. and ease of code navigation. I sorely miss Ctrl+t and Ctrl+] stacking in vim but otherwise it has vim emulator too. I am yet to explore and utilize other features like git.

In this blog we will see how to configure VSCode for PostgreSQL internal development including the development of extensions, proprietary forks. We will talk about two things in this blog 1. how to configure make so that code browsing, navigation, error highlighting and auto-suggestions are sensible 2. how to configure a debugger. These are the two things I struggled with when it came to working with PostgreSQL code in VSCode. Otherwise, you will find plenty of references on C/C++ development in VSCode like this, this and this.

Please feel free to hit me with suggestions, corrections. Drop your VSCode tips and trick or suggest a topic I can cover in my future blog.

1. Getting started with PostgreSQL code

I have a script which clones the PostgreSQL github repository, runs configure. Assume that the code is cloned in "$HOME/vscode_trial/coderoot/pg" directory. coderoot will contain all the VSCode specific files and directories where as coderoot/pg will contain purely PG clone. I am using VSCode version shown in the image on Ubuntu 22.04. I start by clicking VSCode icon in application tray.

Open coderoot folder using File->Open Folder. Save workspace using File->Save Workspace As in coderoot folder. Add folder coderoot/pg using File->Add Folder to Workspace.

2. Setting up make

PostgreSQL uses Makefile to build and manage binaries. VSCode by default uses CMake. So you will need to configure its build tasks to use Make instead of CMake. I have my scripts to build PostgreSQL so I don't need the tool to build binaries per say. But when we point VSCode to PostgreSQL's Makefile, its Intellisense uses Makefile and does a better job at code navigation, error detection and auto-suggestion.

Please install Makefile Tools extension so that VSCode can use make. Point it to the PostgreSQL Makefile selecting the options highlighted in the image below

You will find Makefile Tools extension button on the left side bar. Click it to configure the default tasks or to build binaries. The tool is smart and picks up all the make targets from the Makefile hierarchy. Click the "pencil" icon against "Build target" to choose the target you want and then click the "bug" icon at the top highlighted in the image below. This will run make install. You may ignore an error about launch task not being configured.

3. Debugging a PostgreSQL backend

This configuration baffled me a lot, especially in the newer version of VSCode. Playing with run and build symbol on the left hardly had any success. The trick is to open a source file, any .c file really and then click configuration symbol (highlighted in the image) to configuration debug tasks. I choose C/C++: gcc build and debug active file.

This will open the launch.json file in the workspace. Click Add Configuration button on the bottom right. Most of the time I have to debug a running backend. This requires configuring C/C++ gdb (Attach) option. Add processPid value as shown below. Also provide the path to postgres binary as progream.

Click on the run and debug option from the left bar and choose (gdb) Attach option at the top as shown in the image below.

In order to debug a given backend, click Run->Start Debugging. This should pop-up all PIDs. Choose the one from the list (may want to search postgres). This will attach gdb to that backend and you are ready to go. Enjoy all the blessings of debugging via GUI as described in the documentation here.

More on debugging through VSCode is here.

4. TAP tests

PostgreSQL code include TAP tests written in Perl. You will need Perl navigator and Perl language server and debugger extensions. The second extension is only required if you want to debug TAP tests.