|18:13||• Fixed ticket [892fc34f]: Incorrect query result when a LEFT JOIN subquery is flattened plus 5 other changes (artifact: 879fcac8 user: drh)|
|17:43||Ensure that the query planner knows that any column of a flattened LEFT JOIN can be NULL even if that column is labeled with "NOT NULL". Fix for ticket [892fc34f173e99d8]. (check-in: 48346268 user: dan tags: trunk)|
|16:15||• New ticket [892fc34f] Incorrect query result when a LEFT JOIN subquery is flattened. (artifact: d28d6544 user: drh)|
|Title:||Incorrect query result when a LEFT JOIN subquery is flattened|
|Last Modified:||2017-06-20 18:13:44|
|Version Found In:||3.19.3|
drh added on 2017-06-20 16:15:03:
The following SQL returns a different result in SQLite version 3.19.3 compared to SQLite version 3.18.0 and PostgreSQL. The result is also different if automatic indexes are disabled using "PRAGMA automatic_index=OFF".
CREATE TABLE t1(id INTEGER PRIMARY KEY); CREATE TABLE t2(id INTEGER PRIMARY KEY, c2 INTEGER); CREATE TABLE t3(id INTEGER PRIMARY KEY, c3 INTEGER); INSERT INTO t1(id) VALUES(456); INSERT INTO t3(id) VALUES(1),(2); SELECT t1.id, x2.id, x3.id FROM t1 LEFT JOIN (SELECT * FROM t2) AS x2 ON t1.id=x2.c2 LEFT JOIN t3 AS x3 ON x2.id=x3.c3;
This problem was introduced by the LEFT JOIN subquery flattener optimization of check-in [41c27bc0ff] (which is also the cause of other bugs such as [cad1ab4cb7b0] and [7fde638e94287d]). The problem first appeared in the 3.19.0 release (2017-05-22).
This problem was reported on the SQLite users mailing list by Eric Sink.