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List:       pgsql-bugs
Subject:    Re: BUG #17255: Server crashes in index_delete_sort_cmp() due to race condition with vacuum
From:       Dmitry Dolgov <9erthalion6 () gmail ! com>
Date:       2021-10-31 19:20:51
Message-ID: 20211031192051.e3r2uxft3bulymrr () localhost
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> On Sat, Oct 30, 2021 at 02:39:48PM -0700, Andres Freund wrote:
> > In my case it crashed on pg_unreachable (which is an abort, when asserts
> > are enabled) inside index_delete_sort_cmp. It seems like item pointers
> > to compare both have the same block and offset number. In the view of
> > the recent discussions I was thinking it could be somehow related to the
> > issues with duplicated TIDs, but delstate->deltids doesn't in fact have
> > any duplicated entries -- so not sure about that, still investigating
> > the core dump.
> 
> I suspect this is the same bug as #17245. Could you check if it's fixed by
> https://www.postgresql.org/message-id/CAH2-WzkN5aESSLfK7-yrYgsXxYUi__VzG4XpZFwXm98LUtoWuQ%40mail.gmail.com
>  
> The crash is somewhere in pg_class, which is also manually VACUUMed by the
> test, which could trigger the issue we found in the other thread. The likely
> reason the loop in the repro is needed is that that'll push one of the indexes
> on pg_class over the 512kb/min_parallel_index_scan_size boundary to start
> using paralell vacuum.

I've applied both patches from Peter, the fix itself and
index-points-to-LP_UNUSED-item assertions. Now it doesn't crash on
pg_unreachable, but hits those extra assertions in the second patch:

	#0  0x00007f251875f2fb in raise () from /lib64/libc.so.6
	#1  0x00007f2518748ef6 in abort () from /lib64/libc.so.6
	#2  0x000056387b62a4c7 in ExceptionalCondition (conditionName=0x56387b6be622 \
"ItemIdIsUsed(iid)", errorType=0x56387b6bc849 "FailedAssertion", \
fileName=0x56387b6bc928 "heapam.c", lineNumber=7467) at assert.c:69  #3  \
0x000056387afb4ba9 in heap_index_delete_tuples (rel=0x7f25195f8e20, \
delstate=0x7ffe817bdf00) at heapam.c:7467  #4  0x000056387afe4a38 in \
table_index_delete_tuples (rel=0x7f25195f8e20, delstate=0x7ffe817bdf00) at \
../../../../src/include/access/tableam.h:1327  #5  0x000056387afe83b7 in \
_bt_delitems_delete_check (rel=0x7f2519601880, buf=182, heapRel=0x7f25195f8e20, \
delstate=0x7ffe817bdf00) at nbtpage.c:1541  #6  0x000056387afe4452 in \
_bt_simpledel_pass (rel=0x7f2519601880, buffer=182, heapRel=0x7f25195f8e20, \
deletable=0x7ffe817bdfb0, ndeletable=55, newitem=0x56387c05cfe0, minoff=1, \
maxoff=271) at nbtinsert.c:2896  #7  0x000056387afe3cb1 in \
_bt_delete_or_dedup_one_page (rel=0x7f2519601880, heapRel=0x7f25195f8e20, \
insertstate=0x7ffe817be3b0, simpleonly=false, checkingunique=true, uniquedup=false, \
indexUnchanged=false) at nbtinsert.c:2709  #8  0x000056387afdea4b in \
_bt_findinsertloc (rel=0x7f2519601880, insertstate=0x7ffe817be3b0, \
checkingunique=true, indexUnchanged=false, stack=0x56387c05d008, \
heapRel=0x7f25195f8e20) at nbtinsert.c:901  #9  0x000056387afdd3c7 in _bt_doinsert \
(rel=0x7f2519601880, itup=0x56387c05cfe0, checkUnique=UNIQUE_CHECK_YES, \
indexUnchanged=false, heapRel=0x7f25195f8e20) at nbtinsert.c:255  #10 \
0x000056387afecfee in btinsert (rel=0x7f2519601880, values=0x7ffe817be510, \
isnull=0x7ffe817be4f0, ht_ctid=0x56387c05b994, heapRel=0x7f25195f8e20, \
checkUnique=UNIQUE_CHECK_YES, indexUnchanged=false, indexInfo=0x56387c05cec8) at \
nbtree.c:199  #11 0x000056387afd7f05 in index_insert (indexRelation=0x7f2519601880, \
values=0x7ffe817be510, isnull=0x7ffe817be4f0, heap_t_ctid=0x56387c05b994, \
heapRelation=0x7f25195f8e20, checkUnique=UNIQUE_CHECK_YES, indexUnchanged=false, \
indexInfo=0x56387c05cec8) at indexam.c:193  #12 0x000056387b08c396 in \
CatalogIndexInsert (indstate=0x56387bfc0388, heapTuple=0x56387c05b990) at \
indexing.c:158  #13 0x000056387b08c51a in CatalogTupleInsert (heapRel=0x7f25195f8e20, \
tup=0x56387c05b990) at indexing.c:231  #14 0x000056387b07ed40 in InsertPgClassTuple \
(pg_class_desc=0x7f25195f8e20, new_rel_desc=0x7f251960fa18, new_rel_oid=957915, \
relacl=0, reloptions=0) at heap.c:984  #15 0x000056387b07eec6 in AddNewRelationTuple \
(pg_class_desc=0x7f25195f8e20, new_rel_desc=0x7f251960fa18, new_rel_oid=957915, \
new_type_oid=957917, reloftype=0, relowner=10, relkind=114 'r', relfrozenxid=412531, \
relminmxid=1, relacl=0, reloptions=0) at heap.c:1056  #16 0x000056387b07f60d in \
heap_create_with_catalog (relname=0x7ffe817bec60 "tmp", relnamespace=16686, \
reltablespace=0, relid=957915, reltypeid=0, reloftypeid=0, ownerid=10, accessmtd=2, \
tupdesc=0x56387bfbb6b0, cooked_constraints=0x0, relkind=114 'r', relpersistence=116 \
't', shared_relation=false, mapped_relation=false, oncommit=ONCOMMIT_NOOP, \
reloptions=0, use_user_acl=true, allow_system_table_mods=false, is_internal=false, \
relrewrite=0, typaddress=0x0) at heap.c:1409  #17 0x000056387b1a9bb7 in \
DefineRelation (stmt=0x56387bf98620, relkind=114 'r', ownerId=10, typaddress=0x0, \
queryString=0x56387bf97810 "CREATE TEMPORARY TABLE tmp (a int PRIMARY KEY);") at \
tablecmds.c:933  #18 0x000056387b47fde1 in ProcessUtilitySlow (pstate=0x56387bfb9890, \
pstmt=0x56387bf989d0, queryString=0x56387bf97810 "CREATE TEMPORARY TABLE tmp (a int \
PRIMARY KEY);", context=PROCESS_UTILITY_TOPLEVEL, params=0x0, queryEnv=0x0, \
dest=0x56387bf98ac0, qc=0x7ffe817bf4a0) at utility.c:1163  #19 0x000056387b47fb3d in \
standard_ProcessUtility (pstmt=0x56387bf989d0, queryString=0x56387bf97810 "CREATE \
TEMPORARY TABLE tmp (a int PRIMARY KEY);", readOnlyTree=false, \
context=PROCESS_UTILITY_TOPLEVEL, params=0x0, queryEnv=0x0, dest=0x56387bf98ac0, \
qc=0x7ffe817bf4a0) at utility.c:1066  #20 0x000056387b47eb01 in ProcessUtility \
(pstmt=0x56387bf989d0, queryString=0x56387bf97810 "CREATE TEMPORARY TABLE tmp (a int \
PRIMARY KEY);", readOnlyTree=false, context=PROCESS_UTILITY_TOPLEVEL, params=0x0, \
queryEnv=0x0, dest=0x56387bf98ac0, qc=0x7ffe817bf4a0) at utility.c:527  #21 \
0x000056387b47d5e8 in PortalRunUtility (portal=0x56387bffb860, pstmt=0x56387bf989d0, \
isTopLevel=true, setHoldSnapshot=false, dest=0x56387bf98ac0, qc=0x7ffe817bf4a0) at \
pquery.c:1155  #22 0x000056387b47d858 in PortalRunMulti (portal=0x56387bffb860, \
isTopLevel=true, setHoldSnapshot=false, dest=0x56387bf98ac0, altdest=0x56387bf98ac0, \
qc=0x7ffe817bf4a0) at pquery.c:1312  #23 0x000056387b47ccdb in PortalRun \
(portal=0x56387bffb860, count=9223372036854775807, isTopLevel=true, run_once=true, \
dest=0x56387bf98ac0, altdest=0x56387bf98ac0, qc=0x7ffe817bf4a0) at pquery.c:788  #24 \
0x000056387b475fad in exec_simple_query (query_string=0x56387bf97810 "CREATE \
TEMPORARY TABLE tmp (a int PRIMARY KEY);") at postgres.c:1214  #25 0x000056387b47ab2b \
in PostgresMain (dbname=0x56387bfc3748 "regression", username=0x56387bfc3728 \
"erthalion") at postgres.c:4497  #26 0x000056387b3a636f in BackendRun \
(port=0x56387bfbb460) at postmaster.c:4560  #27 0x000056387b3a5c60 in BackendStartup \
(port=0x56387bfbb460) at postmaster.c:4288  #28 0x000056387b3a1e81 in ServerLoop () \
at postmaster.c:1801  #29 0x000056387b3a1630 in PostmasterMain (argc=3, \
argv=0x56387bf91ca0) at postmaster.c:1473  #30 0x000056387b297f62 in main (argc=3, \
argv=0x56387bf91ca0) at main.c:198

The ItemId in question:

	>>> p *iid
	$2 = {
	  lp_off = 0,
	  lp_flags = 0,
	  lp_len = 0
	}


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