Well, he advised on using tools like Splunk which can do all that for you. But I'm pretty sure they use database internally. So conflict advices I'd say.

Splunk, last I checked, used PostgreSQL for it's backend. While maybe badly worded, my point was more toward the users who have a two column log table with a timestamp and a syslog style line of text. The problem with "advice" posts like these is you can't cover every possible scenario without confusing the less experienced readers. Do I think loggly or splunk cloud should store their logs as flat files? Hell no, their app IS logging. But in the general case of application architecture I don't think it is appropriate or terribly useful for most. I know they say "never say never", but I felt it justified when I believe it's a bad idea in 99% of apps.

It's really more about using the right tool for the job, Splunk, Loggly, NoSQL solutions, etc. are a MUCH better fit than an RDBMS for this sort of work.

Splunk certainly does NOT use Postgres for it's backend(!)

It uses custom index files stored on a filesystem.

It can also connect to MySQL[1] and to HBase[2], but its own data is kept in its own index.

[1] http://blogs.splunk.com/2011/12/20/swimming-with-dolphins/

[2] http://blogs.splunk.com/2011/12/05/introducing-shep/

Makes sense, it's been a long time since I installed or had shell access to a Splunk box, I just remember it needing PG installed. Likely that's changed over the years.