The prebuilt catalog never merged. `mergeArtifactRows` positions itself
with `WHERE mbid > ? ORDER BY mbid LIMIT 1 OFFSET ?` against the
attached artifact, and it bound that cursor as a Go `string` while
`cmd/indexexport` publishes `explore_index.mbid` as 16 raw bytes — the
storage change that took the table from 677 MB to 389 MB.
SQLite does not coerce between TEXT and BLOB and orders every blob after
every text value, so against a byte column the predicate was not wrong
but unconditional: `mbid > <text>` matched the whole artifact, so the
bound the walk looked up was the same row every time and the cursor
never advanced, and `mbid <= <text>` matched nothing, so no batch
merged. No error, no rows, no state change — a fresh install sat at "0
of 1,077,893 rows" burning a core indefinitely, which is what it did
here for a day, while Explore showed only the rows the library scan and
the lazy artist enrichment had produced and popularity for none of the
catalog.
The cursor is now an `artifactKey`, typed to the encoding
`artifactStoresText` reports for the file it is attached to, so the
comparison is made in the same type as the column it is made against.
Two things guard the class rather than the instance: a nil key binds as
an empty value instead of SQL NULL, because `mbid > NULL` agrees with
nothing and would import nothing just as silently; and the walk returns
an error when its bound does not strictly advance, because the failure
here is silence and the next one should be a failed job with a reason.
It was never caught because the fixture that guards the walk writes the
old text encoding, and the only compact fixture is a single row — below
`artifactMergeBatch`, so the bound query never ran at all. The walk is
now covered on both encodings, across several batch boundaries.
Closes#258
yonlu
d4ea14ca5c