Consider the following test case:

CREATE TABLE T0(c0 BOOL);
INSERT INTO T0(c0) VALUES (true);
SELECT * FROM t0 WHERE NOT (c0 != 2 AND c0) -- expected: {}, actual: {TRUE}

Unexpectedly, H2 fetches a row, while none is expected. Omitting the NOT results in the row being fetched as well, which is as expected. I found this based on commit 59fb36c.

I have started working on a SQLancer implementation for H2, which found this bug using the TLP oracle and the following discrepancy between the result sets:

CREATE TABLE T0(c0 BOOL);
INSERT INTO T0(c0) VALUES (true);
SELECT * FROM t0; -- {TRUE}
SELECT * FROM t0 WHERE c0 != 2 AND c0 UNION ALL SELECT * FROM t0 WHERE NOT (c0 != 2 AND c0) UNION ALL SELECT * FROM t0 WHERE (c0 != 2 AND c0) IS NULL; -- {TRUE, TRUE}

Addresses sqlancer/sqlancer#23. I can continue working on the H2 implementation and reporting bugs if there is an interest, and if (most of) the bugs I'm reporting are fixed within a couple of days.