From: Tom Lane <tgl@sss.pgh.pa.us>
To: Mark Dilger <mark.dilger@enterprisedb.com>
cc: Robert Haas <robertmhaas@gmail.com>, Peter Geoghegan <pg@bowt.ie>,
        "Andrey M. Borodin" <x4mmm@yandex-team.ru>,
        Stephen Frost <sfrost@snowman.net>,
        Michael Paquier <michael@paquier.xyz>, Amul Sul <sulamul@gmail.com>,
        Dilip Kumar <dilipbalaut@gmail.com>,
        Andres Freund <andres@anarazel.de>,
        PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: new heapcheck contrib module
In-reply-to: <D9BF3A6E-36E7-46E2-A3A1-8571B53A53D8@enterprisedb.com>
References: <12ED3DA8-25F0-4B68-937D-D907CFBF08E7@enterprisedb.com>
 <20200420194210.sevnpi4lyghoanxi@alap3.anarazel.de>
 <23E60C3C-C20A-4508-84AC-E0CEA59E784A@enterprisedb.com>
 <CA+TgmobAm8vB1MNQ1taO1et+HxTN8ULnQvEG+grNDqNQTBjbtA@mail.gmail.com>
 <F845AC50-A479-43F3-ADFB-861A4D2AD287@enterprisedb.com>
 <5F743835-3399-419C-8324-2D424237E999@enterprisedb.com>
 <CAFiTN-syyHc3jZoou51v0SR8z0POoNfktqEO6MaGig4YS8mosA@mail.gmail.com>
 <E6F4258A-B661-4F2C-8A35-278C9436930A@enterprisedb.com>
 <CAFiTN-s-VX3DLfqv7OOo0zGCTOZ3xVU9UZ6GgzBZdJTPNnYFNg@mail.gmail.com>
 <885D2EC9-7D06-4903-A17D-72C184A1E1C5@enterprisedb.com>
 <CAFiTN-uYg_PiZ854=5R-D9skratapAHKhaDAG7fhJv-Vn5UhaQ@mail.gmail.com>
 <5CC85F28-F210-47AC-8DA8-EC4E82AF3FD5@enterprisedb.com>
 <CAFiTN-sP5iFJGERTq4a4OLTCzjZKhLC5P6_k2bxQKXnuvdmzGA@mail.gmail.com>
 <CAFiTN-tTg0R5AHvXC1ro9XphroX1wUtc5t91hU_+7DeGTpE5VQ@mail.gmail.com>
 <0C0349EB-DD85-4DA8-82C7-DF70AB714592@enterprisedb.com>
 <BA6E870F-241C-4DDB-B92D-DB39E679C7D4@enterprisedb.com> <CA+Tgm!
 ! ! ! ! ! ! ! ! !
 obQUdfM2Q7WAR606RR2YehCZ5GHRKBc-VWfRj-1ZUKqDA@mail.gmail.com>
 <C4A3E5AE-CBB2-4E3F-8BAE-29EE216762C2@enterprisedb.com>
 <CAAJ_b96_Xr2a+D0j8xKbOnCzURcVQm0V2DS+T_pfc+wt3BpL8g@mail.gmail.com>
 <9DF93B83-FE46-4EC4-A99D-77A60729FD2D@enterprisedb.com>
 <CA+TgmoZT3kCOaKq6=m5wHGKh_9XQDbCC1LZXL6w_+NMB-n1+mw@mail.gmail.com>
 <CAAJ_b94hsrF4x7UKQj03416fAEXJorUpZ9WhsZZjqgv-4+Wg9A@mail.gmail.com>
 <50F6468F-5A5E-412A-86EC-DF24B549D733@enterprisedb.com>
 <CAAJ_b94+A1Gk5r5sBYbYM2K5hH_gyp_o=+gwJuJhn5ZEm5_rqw@mail.gmail.com>
 <CAAJ_b94Wh_7kM9JuJk7wnNsYSNPdSzz35cOEaE_ZRnPcqvupCg@mail.gmail.com>
 <7D603B53-8078-4AF0-851B-803FF4416501@enterprisedb.com>
 <CA+TgmoZbPtTgkQBGoco39uqKUWuv=0+TOkiNcCuqWWvUkJVuxQ@mail.gmail.com>
 <A4C9E0AE-46BA-457F-A445-4527E5AA5E3C@enterprisedb.com>
 <98265AA9-7BDC-4708-9348-CC1B173BBE1D@enterprisedb.com>
 <CA+Tgmoam+pnGKhWS+RAYCk1eqjhbAPX7Vm69g1VF56xwyxXw+g@mail.gmail.com>
 <209783.1603313248@sss.pgh.pa.us>
 <77A60E99-6054-40FD-A5D6-769C287D4A0F@enterprisedb.com>!
  <! CA! +T! gm! oa! D5! K6! Uh! O2!
 zddxVCDY2TcR9wSLVurhQYAYpQ0VZPec0og@mail.gmail.com>
 <CA+TgmobGxdm8Tsxawt7LW-qigHRHxD+b17PC+ft9EE+6pMhC9w@mail.gmail.com>
 <721BFA83-EA6F-463D-A9DF-CE78A318B73A@enterprisedb.com>
 <2A7DA1A8-C4AA-43DF-A985-3CA52F4DC775@enterprisedb.com>
 <<CA+TgmoaAG0BVk4b6iOYNCeALQ+4DGLmCbqYXqumK1noGq8UpnA@mai
Comments: In-reply-to Mark Dilger <mark.dilger@enterprisedb.com>
	message dated "Fri, 23 Oct 2020 11:20:40 -0700"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <223058.1603479060.1@sss.pgh.pa.us>
Content-Transfer-Encoding: quoted-printable
Date: Fri, 23 Oct 2020 14:51:01 -0400
Message-ID: <223059.1603479061@sss.pgh.pa.us>
Precedence: bulk

Hmm, we're not out of the woods yet: thorntail is even less happy
than before.

https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=3Dthorntail&dt=3D2=
020-10-23%2018%3A08%3A11

I do not have 64-bit big-endian hardware to play with unfortunately.
But what I suspect is happening here is less about endianness and
more about alignment pickiness; or maybe we were unlucky enough to
index off the end of the shmem segment.  I see that verify_heapam
does this for non-redirect tuples:

            /* Set up context information about this next tuple */
            ctx.lp_len =3D ItemIdGetLength(ctx.itemid);
            ctx.tuphdr =3D (HeapTupleHeader) PageGetItem(ctx.page, ctx.ite=
mid);
            ctx.natts =3D HeapTupleHeaderGetNatts(ctx.tuphdr);

with absolutely no thought for the possibility that lp_off is out of
range or not maxaligned.  The checks for a sane lp_len seem to have
gone missing as well.

			regards, tom lane