The backfill stamp read max(id) of images and versions and max(rowid)
of keywords. None of those tables is AUTOINCREMENT, so SQLite hands a
freed newest id out again: empty the trash of the newest photograph and
scan a new one, or let a local folder's walk delete a renamed file's row
and insert the new name in the same pass, and the new image takes the
old id. max(id) does not move, nor does count(*), and when a newer
version elsewhere keeps max(versions.id) still too, the stamp matched
and the open skipped the backfill.
That row is exactly one that needs it. Neither scan path creates the
default version: scan::persist and walk insert the image and leave the
version, the RAW/JPEG pairing and the keyword terms to the next open.
Skipped, the image went without them until the app restarted, so a
rating or a pulled sidecar judgement had no version to land on and a
JPEG beside its RAW showed twice.
The stamp now carries the newest row's content: the newest image's id,
path, added time and whether it has a version; the newest version's id
and image; the newest assignment's rowid, version and word. Whether the
newest image has a version is the part that cannot be fooled - after a
backfill every image has one, and a row that has just taken a freed id
has none - so the two stamps differ even when the same file comes back
at the same id in the same second. Still one statement: three reverse
rowid scans that stop at the first row, and one probe of versions_image.
An open that skips still costs ~1 ms on the reference catalog copy.
This closes the hole in the stamp itself rather than by a forget() at
each delete site, so a delete path added later, or one in another
process, cannot reopen it. Two tests delete the newest image and insert
another at the freed id on a separate connection, with a newer version
elsewhere holding max(versions.id); both fail against the old stamp.
dtourolle
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