Ask HN: SQL engine reclaiming space from DELETEs

A database storage engine, a decent one by modern standards at least, has to do some things in background and rewrite the data continuously either way. Log structured with all the scrubbing, merging, compression, optimizations, etc. naturally allows for a tunable unused space pressure, merging/moving things from tail to reuse the space as aggressively as necessary. And if the log is spread across many files, it's even possible to release unused files to the filesystem by unlinking them, although this is not really important for DELETEs, only for shrinking, scaling down.

So, it's definitely a good way to design a databases storage engine. But there isn't one open source as far as I know. There are some better than default choices though.

Yep, you're describing a typical design of a DB. I'm looking for an alternative design. I'm guessing it could use multiple small files (a few MBs) and merge them to avoid fragmentation.

Regular VACUUM only marks space as available for reuse. VACUUM FULL returns space to the OS but it requires an exclusive lock and a multi-hour run for a large table.