Re: pg19b1: TRAP: failed Assert("pgstat_bktype_io_stats_valid(bktype_shstats, MyBackendType)")

I think the assert in pgstat_io_flush_cb() after 999dec9ec6a comes from IO
stats on the foreign IO path.
When AsyncReadBuffers() finds IO already in progress, it sets foreign_io
and returns without counting a read. But WaitReadBuffers() still calls:
```
pgstat_count_io_op_time(..., IOOP_READ, io_start, 0, 0);
```
The comment there assumes the read was already counted in
AsyncReadBuffers(). That holds for IO we started ourselves, but not when
we're waiting on another backend's IO. With track_io_timing = on, we get
non-zero IOOP_READ time and zero count, and pgstat_bktype_io_stats_valid()
trips on backend exit.

fix proposal:
```
- pgstat_count_io_op_time(io_object,
io_context, IOOP_READ,
-
io_start, 0, 0);
+ if (!operation->foreign_io)
+ pgstat_count_io_op_time(io_object,
io_context, IOOP_READ,
+
io_start, 0, 0);
```

ср, 8 июл. 2026 г. в 19:58, Justin Pryzby <pryzby(at)telsasoft(dot)com>:

> While restoring from backup to v19, I hit a crash adding a unique
> constraint, since 999dec9ec6a "aio: Don't wait for already in-progress
> IO."
>
> The crash is not consistent, and I don't have an easy reproducer, but I
> can tell you that the crash involves the counts<=0 case, with
> IOOBJECT_RELATION / IOCONTEXT_NORMAL / IOOP_READ, and depends on
> maintenance_work_mem=512MB and track_io_timing=1, and always seems to
> happens in a parallel worker.
>
> LOG: background worker "parallel worker" (PID 1475078) was terminated by
> signal 6: Aborted
> DETAIL: Failed process was running: ALTER TABLE ONLY
> public.counter_latest_data
> ADD CONSTRAINT counter_latest_data_counter_id_site_id_key
> UNIQUE (counter_id, site_id);
> ALTER TABLE public.counter_latest_data CLUSTER ON
> counter_latest_data_counter_id_site_id_key;
>
> (gdb) bt
> #0 __pthread_kill_implementation (threadid=<optimized out>,
> signo=signo(at)entry=6, no_tid=no_tid(at)entry=0) at ./nptl/pthread_kill.c:44
> #1 0x00007f28d65d49ff in __pthread_kill_internal (threadid=<optimized
> out>, signo=6) at ./nptl/pthread_kill.c:89
> #2 0x00007f28d657fcc2 in __GI_raise (sig=sig(at)entry=6) at
> ../sysdeps/posix/raise.c:26
> #3 0x00007f28d65684ac in __GI_abort () at ./stdlib/abort.c:73
> #4 0x00005596eca9bec6 in ExceptionalCondition
> (conditionName=conditionName(at)entry=0x5596ecc47230
> "pgstat_bktype_io_stats_valid(bktype_shstats, MyBackendType)",
> fileName=fileName(at)entry=0x5596ecc471d8
> "../postgresql/src/backend/utils/activity/pgstat_io.c",
> lineNumber=lineNumber(at)entry=228) at
> ../postgresql/src/backend/utils/error/assert.c:65
> #5 0x00005596ec979b6d in pgstat_io_flush_cb (nowait=<optimized out>) at
> ../postgresql/src/backend/utils/activity/pgstat_io.c:228
> #6 0x00005596ec9758ba in pgstat_report_stat (force=force(at)entry=true) at
> ../postgresql/src/backend/utils/activity/pgstat.c:810
> #7 0x00005596ec975a9c in pgstat_shutdown_hook (code=<optimized out>,
> arg=<optimized out>) at
> ../postgresql/src/backend/utils/activity/pgstat.c:646
> #8 0x00005596ec92e901 in shmem_exit (code=code(at)entry=0) at
> ../postgresql/src/backend/storage/ipc/ipc.c:250
> #9 0x00005596ec92ea74 in proc_exit_prepare (code=code(at)entry=0) at
> ../postgresql/src/backend/storage/ipc/ipc.c:199
> #10 0x00005596ec92eb2e in proc_exit (code=code(at)entry=0) at
> ../postgresql/src/backend/storage/ipc/ipc.c:112
> #11 0x00005596ec89f2f0 in BackgroundWorkerMain (startup_data=<optimized
> out>, startup_data_len=<optimized out>) at
> ../postgresql/src/backend/postmaster/bgworker.c:853
> #12 0x00005596ec8a1a4d in postmaster_child_launch
> (child_type=child_type(at)entry=B_BG_WORKER, child_slot=239,
> startup_data=startup_data(at)entry=0x55972a7244d8,
> startup_data_len=startup_data_len(at)entry=1472,
> client_sock=client_sock(at)entry=0x0) at
> ../postgresql/src/backend/postmaster/launch_backend.c:263
> #13 0x00005596ec8a34bd in StartBackgroundWorker (rw=0x55972a7244d8) at
> ../postgresql/src/backend/postmaster/postmaster.c:4176
> #14 maybe_start_bgworkers () at
> ../postgresql/src/backend/postmaster/postmaster.c:4341
> #15 0x00005596ec8a4e05 in LaunchMissingBackgroundProcesses () at
> ../postgresql/src/backend/postmaster/postmaster.c:3416
> #16 ServerLoop () at ../postgresql/src/backend/postmaster/postmaster.c:1728
> #17 0x00005596ec8a7257 in PostmasterMain (argc=argc(at)entry=12,
> argv=argv(at)entry=0x55972a6a0ec0) at
> ../postgresql/src/backend/postmaster/postmaster.c:1403
> #18 0x00005596ec5cbd1c in main (argc=12, argv=0x55972a6a0ec0) at
> ../postgresql/src/backend/main/main.c:231
>
> --
> Justin
>
>
>