SQLite has different “modes” to facilitate recovery, this new WAL2 mode addresses the problem in WAL (version 1) where the recovery log could potentially grow very large.
It’s solving a real problem, but not considered stable for production yet.
It’s solving a real problem, but not considered stable for production yet.
We have been using SQLite in WAL mode for over half a decade and never witnessed this. Several of our databases can see concurrent access from hundreds of users with transactions in the 1-10 megabyte range, so I find it a bit odd this never came up.
From the link, "if a writer writes to the database while a checkpoint is ongoing [...] it does mean that the wal file may grow indefinitely if the checkpointer never gets a chance to finish without a writer appending to the wal file. There are also circumstances in which long-running readers may prevent a checkpointer from checkpointing the entire wal file - also causing the wal file to grow indefinitely in a busy system."
SQLite runs in a surprising number of places. In an embedded environment disk space may be limited.
I've had to restart services when WAL files had grown to multiple GBs and wouldn't shrink.
The recovery log growing large is explained in [1] - "it does mean that the wal file may grow indefinitely [...] There are also circumstances [...] causing the wal file to grow indefinitely in a busy system."
Not ready for production is [2] - although that is from 2 years ago, the WAL2 branch still isn't merged to trunk [3] which you'd expect if it was ready to go, I think?
[1] https://www.sqlite.org/cgi/src/doc/wal2/doc/wal2.md [2] https://sqlite.org/forum/forumpost/17249fb83a?t=c&unf [3] https://www.sqlite.org/cgi/src/timeline?r=wal2