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From: Tender Wang <tndrwang@gmail.com>
Date: Thu, 19 Mar 2026 20:39:26 +0800
Message-ID: 
 <CAHewXNmSK+gKziAt_WvQoMVWt3_LRVMmRYY9dAbMPMcpPV0QmA@mail.gmail.com>
Subject: Re: More speedups for tuple deformation
To: David Rowley <dgrowleyml@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, John Naylor <johncnaylorls@gmail.com>,
	PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
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Hi David,

David Rowley <dgrowleyml@gmail.com> =E4=BA=8E2026=E5=B9=B43=E6=9C=8817=E6=
=97=A5=E5=91=A8=E4=BA=8C 05:15=E5=86=99=E9=81=93=EF=BC=9A
>
> On Mon, 16 Mar 2026 at 22:17, David Rowley <dgrowleyml@gmail.com> wrote:
> >
> > On Mon, 16 Mar 2026 at 20:01, Tender Wang <tndrwang@gmail.com> wrote:
> > > SELECT * FROM t2, t4 RIGHT OUTER JOIN t0 ON t4.c0 WHERE t4.c1 ORDER B=
Y
> >
> > > server closed the connection unexpectedly
> >
> > Thanks. Looks like I didn't get the startAttr logic correct in
> > nocachegetattr(). Starting by using the attcacheoff of the first NULL
> > attribute isn't valid. It should be the attribute prior to that one.
> >
> > I'm just verifying some code locally now.
>
> Now pushed. Some concerns about the lack of exercise in the tests for
> fastgetattr() for user tables. I ended up testing by injecting the
> following into slot_deform_heap_tuple()

I encountered a crash when doing SQLSmith on TPCH (s=3D1) test.

How to reproduce:
1. prepare TPCH s =3D1 data.
2. Execute the following query

postgres=3D# update public.region set
          r_comment =3D public.region.r_comment
        returning
          5 as c0,
          pg_catalog.bittypmodout(
            cast(public.region.r_regionkey as int4)) as c1;
server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
The connection to the server was lost. Attempting reset: Succeeded.

(gdb) bt
#0  __pthread_kill_implementation (no_tid=3D0, signo=3D6,
threadid=3D140696004203456) at ./nptl/pthread_kill.c:44
#1  __pthread_kill_internal (signo=3D6, threadid=3D140696004203456) at
./nptl/pthread_kill.c:78
#2  __GI___pthread_kill (threadid=3D140696004203456,
signo=3Dsigno@entry=3D6) at ./nptl/pthread_kill.c:89
#3  0x00007ff659450476 in __GI_raise (sig=3Dsig@entry=3D6) at
../sysdeps/posix/raise.c:26
#4  0x00007ff6594367f3 in __GI_abort () at ./stdlib/abort.c:79
#5  0x000055d8ae8cad94 in ExceptionalCondition
(conditionName=3D0x55d8aeac5beb "attlen > 0 || attlen =3D=3D -1",
fileName=3D0x55d8aeac5a18 "execTuples.c", lineNumber=3D1197) at
assert.c:65
#6  0x000055d8ae3afa2e in slot_deform_heap_tuple (slot=3D0x55d8cabf1a58,
tuple=3D0x55d8cabf1ab0, offp=3D0x55d8cabf1ac8, reqnatts=3D2) at
execTuples.c:1197
#7  0x000055d8ae3ae853 in tts_minimal_getsomeattrs
(slot=3D0x55d8cabf1a58, natts=3D2) at execTuples.c:550
#8  0x000055d8ae06ac3b in slot_getsomeattrs (slot=3D0x55d8cabf1a58,
attnum=3D2) at ../../../../src/include/executor/tuptable.h:380
#9  0x000055d8ae06ac62 in slot_getallattrs (slot=3D0x55d8cabf1a58) at
../../../../src/include/executor/tuptable.h:392
#10 0x000055d8ae06b5f5 in printtup (slot=3D0x55d8cabf1a58,
self=3D0x55d8cab11828) at printtup.c:319
#11 0x000055d8ae6bfd82 in RunFromStore (portal=3D0x55d8cab860a0,
direction=3DForwardScanDirection, count=3D0, dest=3D0x55d8cab11828) at
pquery.c:1089
#12 0x000055d8ae6bf88b in PortalRunSelect (portal=3D0x55d8cab860a0,
forward=3Dtrue, count=3D0, dest=3D0x55d8cab11828) at pquery.c:912
#13 0x000055d8ae6bf4ea in PortalRun (portal=3D0x55d8cab860a0,
count=3D9223372036854775807, isTopLevel=3Dtrue, dest=3D0x55d8cab11828,
altdest=3D0x55d8cab11828, qc=3D0x7ffe1b92e4f0) at pquery.c:760
#14 0x000055d8ae6b7c2b in exec_simple_query (
    query_string=3D0x55d8caadb4b0 "update public.region set \n
r_comment =3D public.region.r_comment\n        returning \n          5
as c0, \n          pg_catalog.bittypmodout(\n", ' ' <repeats 12
times>, "cast(public.region.r_regionkey as int4)) a"...)
    at postgres.c:1278
#15 0x000055d8ae6bd47b in PostgresMain (dbname=3D0x55d8cab218d0
"postgres", username=3D0x55d8cab218b8 "ubuntu") at postgres.c:4810
#16 0x000055d8ae6b3068 in BackendMain (startup_data=3D0x7ffe1b92e7a0,
startup_data_len=3D24) at backend_startup.c:124
#17 0x000055d8ae5a17a6 in postmaster_child_launch
(child_type=3DB_BACKEND, child_slot=3D2, startup_data=3D0x7ffe1b92e7a0,
startup_data_len=3D24, client_sock=3D0x7ffe1b92e800) at
launch_backend.c:268
#18 0x000055d8ae5a8290 in BackendStartup (client_sock=3D0x7ffe1b92e800)
at postmaster.c:3606
#19 0x000055d8ae5a57d2 in ServerLoop () at postmaster.c:1713
#20 0x000055d8ae5a509c in PostmasterMain (argc=3D3, argv=3D0x55d8caad5b30)
at postmaster.c:1403
#21 0x000055d8ae430b37 in main (argc=3D3, argv=3D0x55d8caad5b30) at main.c:=
231
(gdb) f 6
#6  0x000055d8ae3afa2e in slot_deform_heap_tuple (slot=3D0x55d8cabf1a58,
tuple=3D0x55d8cabf1ab0, offp=3D0x55d8cabf1ac8, reqnatts=3D2) at
execTuples.c:1197
1197 pg_assume(attlen > 0 || attlen =3D=3D -1);
(gdb) p attlen
$1 =3D -2

Please take a look.

--=20
Thanks,
Tender Wang