From 2b5407397fb3bfe9e5c1d0f64384b09a21bd9013 Mon Sep 17 00:00:00 2001 From: Fujii Masao Date: Fri, 1 Aug 2025 20:10:57 +0900 Subject: [PATCH v2] Fix assertion failure in pgbench when handling multiple pipeline sync messages. Previously, when running pgbench in pipeline mode with a custom script that triggered retriable errors (e.g., serialization errors), an assertion failure could occur: Assertion failed: (res == ((void*)0)), function discardUntilSync, file pgbench.c, line 3515. The root cause was that pgbench incorrectly assumed only a single pipeline sync message would be received at the end. In reality, multiple pipeline sync messages can be sent and must be handled properly. This commit fixes the issue by updating pgbench to correctly process multiple pipeline sync messages, preventing the assertion failure. Back-patch to v15, where the bug was introduced. Author: Fujii Masao Reviewed-by: Tatsuo Ishii Discussion: https://postgr.es/m/CAHGQGwFAX56Tfx+1ppo431OSWiLLuW72HaGzZ39NkLkop6bMzQ@mail.gmail.com Backpatch-through: 15 --- src/bin/pgbench/pgbench.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/src/bin/pgbench/pgbench.c b/src/bin/pgbench/pgbench.c index 497a936c141..125f3c7bbbe 100644 --- a/src/bin/pgbench/pgbench.c +++ b/src/bin/pgbench/pgbench.c @@ -3495,6 +3495,8 @@ doRetry(CState *st, pg_time_usec_t *now) static int discardUntilSync(CState *st) { + bool received_sync = false; + /* send a sync */ if (!PQpipelineSync(st->con)) { @@ -3509,10 +3511,21 @@ discardUntilSync(CState *st) PGresult *res = PQgetResult(st->con); if (PQresultStatus(res) == PGRES_PIPELINE_SYNC) + received_sync = true; + else if (received_sync) { - PQclear(res); - res = PQgetResult(st->con); + /* + * PGRES_PIPELINE_SYNC must be followed by another + * PGRES_PIPELINE_SYNC or NULL; otherwise, assert failure. + */ Assert(res == NULL); + + /* + * Reset ongoing sync count to 0 since all PGRES_PIPELINE_SYNC + * results have been discarded. + */ + st->num_syncs = 0; + PQclear(res); break; } PQclear(res); -- 2.50.1