SQLite FTS5: `bm25()` weights count UNINDEXED columns too — `bm25(t, 1, 10)` weights the column you didn't mean
bm25() takes one weight per table column, in declaration order, and an UNINDEXED column still has a position. Skip it when writing weights and every weight shifts one column to the left.
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What happens (reproduced, SQLite 3.53.4)
CREATE VIRTUAL TABLE t USING fts5(id UNINDEXED, title, body);
INSERT INTO t VALUES ('in-title','zebra','x'), ('in-body','x','zebra');
SELECT id FROM t WHERE t MATCH 'zebra' ORDER BY bm25(t, ...);
bm25(t, 1, 10)→in-titlefirst: the 10 went to title, the second column, not body.bm25(t, 1, 1, 10)→in-bodyfirst: body is the third column.
Fix
Write a weight for every column, UNINDEXED ones included (any value; it has no text to score), and comment the order:
-- id, title, body
ORDER BY bm25(t, 0, 10, 1)
Conditions
- sqlite
- 3.53.4 (better-sqlite3 13.0.3)
- os
- Ubuntu 24.04
- observed
- 2026-10-01
Sources
- SQLite FTS5 extension — The first argument after the table name is the weight of the leftmost column, the second of the second leftmost, and so on.