Consider the following example:

PRAGMA journal_mode=OFF;
PRAGMA main.cache_size=0;
CREATE TABLE IF NOT EXISTS t0 (c0);
CREATE INDEX i0 ON t0(1);
DROP INDEX "i0";
INSERT OR IGNORE INTO t0(c0) VALUES (1), (2);
CREATE UNIQUE INDEX i0 ON t0(1); -- UNIQUE constraint failed: index 'i0'
CREATE UNIQUE INDEX i0 ON t0(1); -- database disk image is malformed

Is this expected? The documentation mentions that the ROLLBACK statement cannot be used with journal_mode=OFF, but it does not mention failed index creation.

This is the expected behavior when there is no journal available to rollback a partially completed operation that fails due to a constraint. The documentation has been strengthened to try to make this clear. And PRAGMA journal_mode=OFF is now disallowed if SQLITE_DBCONFIG_DEFENSIVE is turned on.