Re: Fix missing EvalPlanQual recheck for TID scans

On Sat, Sep 13, 2025 at 3:12 PM, Sophie Alpert <pg(at)sophiebits(dot)com> wrote:
> And indeed, like I mentioned in my previous message, my isolation test
> `permutation tid1 tidsucceed2 c1 c2 read` from eval-plan-qual.spec in
> my patch will fail if Recheck were to return false in this case. Though
> somewhat contrived, you can imagine this happening with multiple
> sessions driven by the same application:

Another case where returning FALSE does not give the correct behavior is when two relations are involved, only one of which is modified:

S1: BEGIN;
S2: BEGIN;
S1: UPDATE accounts SET balance = balance + 100 WHERE ctid = '(0,1)' RETURNING accountid, balance;
S2: SELECT * FROM accounts JOIN accounts_ext USING (accountid) WHERE accounts_ext.ctid = '(0,1)' FOR UPDATE OF accounts;
S1: COMMIT;
S2: COMMIT;

In my patch the S2 query correctly returns one row, whereas with your proposed change it incorrectly returns none.

accountid|balance|balance2|balance|other|newcol|newcol2
---------+-------+--------+-------+-----+------+-------
checking | 700| 1400| 600|other| 42|

Sophie