Re: [boost] NuDB: A fast key/value insert-only database for SSD drives in C++11

Subject: Re: [boost] NuDB: A fast key/value insert-only database for SSD drives in C++11
From: Vinnie Falco (vinnie.falco_at_[hidden])
Date: 2017-03-29 13:53:27

On Wed, Mar 29, 2017 at 9:49 AM, Peter Dimov via Boost
<boost_at_[hidden]> wrote:
> But you do guarantee that if this insert is present in the recovered
> database, all earlier inserts are too, right? This is what you need for the
> letter C.

Yes. NuDB buffers insertions into memory (that's what the "cache" and
"pool" classes are for). Once per second, or sooner depending on the
insertion load, the implementation runs a "commit".

The commit process acquires all the insertions buffered up to that
point, renders the changed buckets in memory, creates a backup of the
buckets in their before-modified state to the log file, applies the
changes, and then resets the log file.

The commit process is atomic, either it all goes through or it fails
and the database is recovered to the state before the commit.