Just a Theory

By David E. Wheeler

Sqitch Update

A quick update on Sqitch. I started implementation about a couple of weeks ago. It’s coming a long a bit more slowly than I’d like, given that I need to give a presentation on it soon. But I did things a little differently than I usually do with project like this: I wrote documentation first. In addition to the basic docs I posted a couple weeks back, I’ve written a tutorial. I put quite a lot of time into it, studying the Git interface as I did so, to try to develop useful workflows. The nice thing about this it that it will not only serve as the foundation for my presentation (PHEW! Half the work done already!), but it also serves as a design specification.

So I’ve been diligently plugging away on it, and have uploaded a couple of trial releases to CPAN. So far, we have decent support for:

  • sqitch help and sqitch help command. The latter only works for the implemented commands, of course.
  • sqitch config, which is a near perfect duplication of git-config, thanks to the very useful Config::GitLike. It supports a local, project-specific config file, a user config file, and a system config file.
  • sqitch init, which creates a new project by creating directories for the deploy, revert, and test scripts, and writes a project-specific config file. This file has options you specify in the call to sqitch (such as the database engine you plan to use), and all unmodified settings or settings set in user or system configuration are written out as comments.

So yeah, not a ton so far, but the foundations for how it all goes together are there, so it should take less time to develop other commands, all things being equal.

Next up:

  • sqitch add-step, which will create deploy and revert scripts for a new step, based on simple templates.
  • sqitch deploy, which is the big one. Initial support will be there for PostgreSQL and SQLite (and perhaps MySQL).

Interested in helping out?

  • I’m going to need a parser for the plan file pretty soon. The interface will need an iterator to move back and forth in the file, as well as a way to write to the file, add steps to it, etc. The grammar is pretty simple, so anyone familiar with parsers and iterators could probably knock something out pretty quickly.

  • The interface for testing needs some thinking through. I had been thinking that it could be something as simple as just diffing the output of a script file against an expected output file, at least to start. One could even use pgTAP or MyTAP in such scripts, although it might be a pain to get the output exactly right for varying environments. But maybe that doesn’t matter for deployment, so much? Because it tends to be to a more controlled environment than your typical open-source library test suite, I mean.

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