Well I've finally fulfilled one of my 2013 New Year's resolutions, which was to write some kind of foreign data wrapper, so with no further ado here is the initial implementation. It is basically working but is still very much in the proof-of-concept/unstable/may-eat-your-data stage. Having said that, if anyone has a practical use for this I'd be very interested to hear about it - my main motivation for creating this FDW is to learn more about PostgreSQL internals.
PostgreSQL 9.3 RC1 was released the other day, and despite the dire warnings I couldn't resist putting it on this server to try out some of the new functionality in live operation. Admittedly it's not a real "production server" as having the database crash or mangle the data beyond repair would be merely an annoyance to myself and is nothing that can't be recovered from backups, so it's a good way of testing the new release. I've had good experiences with release candidates in the past, and probably the worst that could happen is the discovery of some issue requiring a bump of the catalog version number before final release, which means I'd have to upgrade from backups (which would probably mean whole minutes of downtime).
Disclaimer, esp. for any of my colleagues reading this wondering if I'm insane: there's no way I would ever do this with a genuine production installation.
Anyway, a full day's worth of log files shows no errors or other issues associated with the new release. This is particularly gratifying as there's now a (modest) custom background worker running which is giving me a warm tingly feeling and has got me thinking about ideas for new ones. I also feel a materialized view coming on, and I'm sure there's some way I could contrive a justification for using a writeable foreign data wrapper.
Thanks to everyone who has put so much effort into this release - I'm looking forward to the day when it can run in production for real.
A while back I posted some SQL which helps track of changes to the PostgreSQL settings file. I've found it useful when benchmarking tests with different settings, but unfortunately the pg_settings_log() function needs to be run manually after each setting change. However that sounds like something which a custom background worker (new in 9.3) could handle - basically all the putative background worker would need to do is execute the pg_settings_log() function whenever the server starts (or restarts) or receives SIGHUP.
This turned out to be surprisingly easy to implement. Based off the example contrib module and Michael Paquier's excellent posts, this is the code. Basically all it does is check for the presence of the required database objects (a function and a table) on startup, executes pg_settings_log() on startup, and adds a signal handler for SIGHUP which also calls pg_settings_log().
Having recently posted some thoughts on Shaun Thomas' ""PostgreSQL Backup and Restore How-to" review", Packt asked me if I'd like to review the new "Instant PostgreSQL Starter" by Daniel K. Lyons and kindly provided me with access to the ebook version. As I'm happily in a situation where I may need to introduce PostgreSQL to new users, I was interested in taking a look and here's a quick overview.
It follows the same "Instant" format as the backup booklet, which I quite like as it provides a useful way of focussing on particular aspects of PostgreSQL without being bogged down in reams of tl;dr documentation. "Instant Pg Starter" is divided into three sections:
- Quick start – creating your first table
- Top 9 features you need to know about
Having worked with PostgreSQL continuously since 2001, I'd like to think there's nothing I don't know about backing up and restoring. However, experience shows that a) it's all too easy to develop "muscle memory" for a certain way of doing things, and b) PostgreSQL has a pesky habit of developing useful new features which fly under the radar if you're not paying sufficient attention to the release notes, so any opportunity to review things from a fresh perspective is a welcome one.
I ordered the paper version of "PostgreSQL Backup and Restore How-to" by Shaun Thomas from Amazon Japan for a tad under 2,000 yen, which is a little on the expensive side for what was described as a "booklet" (and four times the price of the eBook version), but I have a (meagre) book budget to burn and I have this old-fashioned habit of scribbling notes on margins and making little bookmarks from Post-It notes etc., also it's nice to spend some time not staring at a screen. To my surprise it arrived less than 48 hours after ordering - upon closer examination it turned out the book was actually printed by Amazon in Japan, which is kind of nifty.
First impression: it's a very thin volume - 42 actual content pages - so is genuinely a booklet. On the other hand, bearing in mind I've got a bookshelf full of largely unread weighty tomes, less can be more.
The booklet's table of contents, as lifted directly from the publisher's site, is:
- Getting a basic export (Simple)
- Partial database exports (Simple)
- Restoring a database export (Simple)
- Obtaining a binary backup (Simple)
- Stepping into TAR backups (Intermediate)
- Taking snapshots (Advanced)
- Synchronizing backup servers (Intermediate)
- Restoring a binary backup (Simple)
- Point in time recovery (Intermediate)
- Warm and hot standby restore (Intermediate)
- Streaming replication (Advanced)