Installed sqlite and could reproduce locally.

Did some debugging, and found that the DB abstraction layer is riddled with inconsistencies in return types. Just have a look at DatabaseBase::doQuery and it's implementations in DatabaseMysql and DatabaseSqlite.

Looks like this is still an issue indeed.

	/*
	 * @return bool|IResultWrapper
	 * @throws DBError
	 */
	public function delete( $table, $conds, $fname = __METHOD__ );

	/*
	 * @return bool|IResultWrapper True for a successful write query, IResultWrapper object
	 *     for a successful read query, or false on failure if $tempIgnore set
	 * @throws DBError
	 */
	public function query( $sql, $fname = __METHOD__, $tempIgnore = false );

	protected function doQuery( $sql ) {
		/* .. */ $ret = $conn->query( $sql );
		/* .. */ 

		return $ret;
	}

Where mysqli::query does the work for us, and returns true for successful non-read queries per https://secure.php.net/manual/en/mysqli.query.php.

	protected function doQuery( $sql ) {
		$res = $this->getBindingHandle()->query( $sql );
		/* .. */
		$res = new ResultWrapper( $this, $r->fetchAll() );

		return $res;
	}

Here is the cause of the problem. PDO::query does have the return true feature that mysqli does, per https://secure.php.net/manual/en/pdo.query.php. Which means we need to write code to do that for write queries. Currently, the code currently returns ResultWrapper unconditionally for all successful queries.

Change 463640 had a related patch set uploaded (by 星耀晨曦; owner: 星耀晨曦):
[mediawiki/core@master] Coding to handle write queries

https://gerrit.wikimedia.org/r/463640

Change 463640 abandoned by 星耀晨曦:
Coding to handle write queries in sqlite implement

Reason:
Already fixed in https://gerrit.wikimedia.org/r/#/c/mediawiki/core/ /470071/.

https://gerrit.wikimedia.org/r/463640