> On Nov 13, 2025, at 12:02, Chao Li <[email protected]> wrote:
>
>
>
>> On Nov 13, 2025, at 11:47, Fujii Masao <[email protected]> wrote:
>>
>> On Thu, Nov 13, 2025 at 11:21 AM Chao Li <[email protected]> wrote:
>>> I debugged further this morning, and I think I have found the root cause.
>>> Ultimately, the problem is not with discardUntilSync(), instead,
>>> discardAvailableResults() mistakenly eats PGRES_PIPELINE_SYNC.
>>
>> Thanks for debugging!
>>
>> Yes, discardAvailableResults() can discard PGRES_PIPELINE_SYNC,
>> but do you mean that's the root cause of the assertion failure
>> Nagata-san reported?
>> Since that failure can occur even in older branches, I was thinking
>> that newer code
>> like discardAvailableResults() in master isn't the root cause...
>>
>
> I haven’t debugged with old code, but the old code also discard non-NULL
> results:
>
> ```
> - do
> - {
> - res = PQgetResult(st->con);
> - PQclear(res);
> - } while (res);
> + discardAvailableResults(st);
> ```
>
> Which may also discard the sync message. That’s my guess. I can also debug
> the old code this afternoon.
>
I just tried the old code but it didn’t trigger the assert with Yugo’s deadlock
scripts.
I did "git reset --hard a3ea5330fcf47390c8ab420bbf433a97a54505d6”, that is the
previous commit of “—continue-on-error”. And I ran Yugo’s deadlock scripts, but
I didn’t get the assert:
```
% pgbench -n --failures-detailed -M extended -j 2 -c 2 -f deadlock.sql -f
deadlock2.sql evantest
pgbench (19devel)
transaction type: multiple scripts
scaling factor: 1
query mode: extended
number of clients: 2
number of threads: 2
maximum number of tries: 1
number of transactions per client: 10
number of transactions actually processed: 20/20
number of failed transactions: 0 (0.000%)
number of serialization failures: 0 (0.000%)
number of deadlock failures: 0 (0.000%)
latency average = 0.341 ms
initial connection time = 2.637 ms
tps = 5865.102639 (without initial connection time)
SQL script 1: deadlock.sql
- weight: 1 (targets 50.0% of total)
- 12 transactions (60.0% of total)
- number of transactions actually processed: 12 (tps = 3519.061584)
- number of failed transactions: 0 (0.000%)
- number of serialization failures: 0 (0.000%)
- number of deadlock failures: 0 (0.000%)
- latency average = 0.311 ms
- latency stddev = 0.304 ms
SQL script 2: deadlock2.sql
- weight: 1 (targets 50.0% of total)
- 8 transactions (40.0% of total)
- number of transactions actually processed: 8 (tps = 2346.041056)
- number of failed transactions: 0 (0.000%)
- number of serialization failures: 0 (0.000%)
- number of deadlock failures: 0 (0.000%)
- latency average = 0.366 ms
- latency stddev = 0.364 ms
```
Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/
