[czinck]

I think you're mixing 2 things. This is a complete rewrite of an old key-value store (hence the 2 in the name) but comdb2 was always SQL. Comdb2 shares a few things with comdb, but they're really just to make migration easier (the preference for tags in csc2 files instead of usual DDL, and then a tag based API that it looks like we got rid of for this release). Under the covers comdb2 is completely different and as far as I know shares no code with comdb.

[toosleepy]

It wasn't always an SQL system. SQL was added a year or two in its development (with lots of databases already live).

[alexjscotti]

Yep. With a false start or two along the way. One of the most interesting things on this project was repeatedly changing engines while the plane was in the air.

[mponomar]

We've had databases literally up for 10+ years, through 5-6 major version upgrades. There's been one file format change that required downtime very early on.