The reviewed maintenance plan gains workflow_storage. Applying it starts
"Store each workflow once": kind maintenance, records admission,
cancellable, groups changed/protected/errors.
- The promised verified safety backup comes first; a failed backup ends the
job with nothing rewritten. The apply's up-front disk check covers it.
- Old-form rows are rewritten batch by batch on the event loop's executor,
with progress after each committed batch. Cancel stops between batches;
a failed batch rolls back whole and fails the job with a coded message.
Either way every record reads as before and the next apply continues.
- When every row was looked at, "Reclaim space" starts: exclusive (runs
alone), not cancellable. It checks the disk for VACUUM's copies of the
live pages, then sweeps, runs VACUUM and truncates the WAL. If another job
holds the registry it does not start, and the finished migration says so
and names Optimize database.
- No image or video file is opened; tests track every open under the
output folder and compare the media bytes and mtimes.
The workflow storage migration rewrites old-form image rows (text inline)
to document ids, batch by batch:
- Each batch is one BEGIN IMMEDIATE transaction of at most 200 rows or
16 MB of text, found by a rowid range search and read one row at a time.
- Each text is stored or reused, then read back through the one accessor
before its row changes; a text that would not come back identical fails
and rolls back the whole batch.
- A value that is not text stays inline and is counted as protected.
- A crash or a stop leaves committed batches new form and the rest old
form; both read the same, and a rerun continues. No media file is opened.
- Unreferenced documents are swept at the end.
The maintenance preview gains a read-only workflow_storage plan (records to
rewrite, inline bytes where SQLite has octet_length, the Reclaim space and
older-version notes). reclaim_space sweeps, runs VACUUM and truncates the
WAL so the freed pages go back to the disk.
Vito Sansevero