When a scan pull takes in sidecars another device wrote, `apply_judgement`
finds the photographs each one describes with
`source_ref LIKE '{stem}.%'`. SQLite's LIKE folds ASCII case, and nothing
indexes `source_ref` case-insensitively, so every lookup read all 24,000
names of the root through the `(root_id, source_ref)` index: 1.5-2 ms per
sidecar, 520-690 ms for the 342 `.drsc` files the reference catalog has
read. Another device culling a shoot is several hundred of them.
Every name beginning `{stem}.` lies in the half-open range
`[{stem}., {stem}/)` -- `/` is the byte after `.` -- which the unique key
serves as a seek. The rows LIKE matched beyond these differed only in
case, and the check that decides, `sidecar_path(source) == sidecar`, has
always compared exactly and refused them; the escaping of `%` and `_`
goes too, since a range has no wildcards.
persist_bench: 342 lookups 634-691 ms -> 9 ms CPU. Checked against the
reference catalog directly as well: for all 18,430 distinct sidecar
names its images imply, the range and the old LIKE, each filtered by
`sidecar_path`, pick the same photographs. A test pins the neighbours of
the range: a case variant, a longer stem, a subfolder named like the
stem, and a folder whose name holds `%` and `_`.
The XMP reader's LIKE (`xmp_sync::images_for`) is left alone: its check
is case-insensitive, so the range would not be a superset there, and it
only runs when the exact darktable-style name is not found.
dtourolle
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