Re: Potential ABI breakage in upcoming minor releases

On Thu, Nov 14, 2024 at 9:33 PM Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
wrote:

> On 2024-Nov-14, Tom Lane wrote:
>
> > Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> writes:
> > > On 2024-Nov-14, Christoph Berg wrote:
> > >> It didn't actually crash, true.
> >
> > > But timescale did crash:
> >
> > So what is timescale doing differently?
>
> No idea. Maybe a stacktrace from a core would tell us more; but the
> jenkins task doesn't seem to have server logs or anything else to gives
> us more clues.
>

Here is one stack trace from my failure. It's a little inconclusive, but
maybe better brains than mine might realize something:

(gdb) bt
#0 __pthread_kill_implementation (no_tid=0, signo=6, threadid=<optimized
out>) at ./nptl/pthread_kill.c:44
#1 __pthread_kill_internal (signo=6, threadid=<optimized out>) at
./nptl/pthread_kill.c:78
#2 __GI___pthread_kill (threadid=<optimized out>, signo=signo(at)entry=6) at
./nptl/pthread_kill.c:89
#3 0x00007ab10c44526e in __GI_raise (sig=sig(at)entry=6) at
../sysdeps/posix/raise.c:26
#4 0x00007ab10c4288ff in __GI_abort () at ./stdlib/abort.c:79
#5 0x000056b2b0439b70 in ExceptionalCondition (
conditionName=conditionName(at)entry=0x7ab10cad0280 "whichrel >= 0 && whichrel
< mtstate->mt_nrels",
fileName=fileName(at)entry=0x7ab10cad0170
"/home/mats/work/timescale/timescaledb+tam/src/nodes/hypertable_modify.c",
lineNumber=lineNumber(at)entry=1249) at assert.c:66
#6 0x00007ab10caa0c90 in ExecInitUpdateProjection
(mtstate=mtstate(at)entry=0x56b2b0bbf8f0,
resultRelInfo=resultRelInfo(at)entry=0x56b2b0bbfc80) at
/home/mats/work/timescale/timescaledb+tam/src/nodes/hypertable_modify.c:1249

#7 0x00007ab10caa385e in ExecModifyTable
(cs_node=cs_node(at)entry=0x56b2b0bbf2e0,
pstate=0x56b2b0bbf8f0) at
/home/mats/work/timescale/timescaledb+tam/src/nodes/hypertable_modify.c:940
#8 0x00007ab10caa3a83 in hypertable_modify_exec (node=0x56b2b0bbf2e0) at
/home/mats/work/timescale/timescaledb+tam/src/nodes/hypertable_modify.c:174
#9 0x000056b2b011bcba in ExecCustomScan (pstate=<optimized out>) at
nodeCustom.c:121
#10 0x000056b2b0107147 in ExecProcNodeFirst (node=0x56b2b0bbf2e0) at
execProcnode.c:464
#11 0x000056b2b00fed07 in ExecProcNode (node=node(at)entry=0x56b2b0bbf2e0) at
../../../src/include/executor/executor.h:274
#12 0x000056b2b00fed9b in ExecutePlan (estate=estate(at)entry=0x56b2b0bbf030,
planstate=0x56b2b0bbf2e0, use_parallel_mode=<optimized out>,
operation=operation(at)entry=CMD_UPDATE, sendTuples=sendTuples(at)entry=false,
numberTuples=numberTuples(at)entry=0, direction=ForwardScanDirection,
dest=0x56b2b0ba6a68,
execute_once=true) at execMain.c:1654
#13 0x000056b2b00ffb6e in standard_ExecutorRun (queryDesc=0x56b2b0b96780,
direction=ForwardScanDirection, count=0, execute_once=execute_once(at)entry=true)
at execMain.c:365
#14 0x000056b2b00ffcb2 in ExecutorRun
(queryDesc=queryDesc(at)entry=0x56b2b0b96780,
direction=direction(at)entry=ForwardScanDirection, count=count(at)entry=0,
execute_once=execute_once(at)entry=true) at execMain.c:306
#15 0x000056b2b02f108a in ProcessQuery (plan=plan(at)entry=0x56b2b0ba6958,
sourceText=<optimized out>, params=0x0, queryEnv=0x0,
dest=dest(at)entry=0x56b2b0ba6a68,
qc=qc(at)entry=0x7ffc452f04e0) at pquery.c:160
#16 0x000056b2b02f1bf2 in PortalRunMulti (portal=portal(at)entry=0x56b2b0af24d0,
isTopLevel=isTopLevel(at)entry=true, setHoldSnapshot=setHoldSnapshot(at)entry=false,
dest=dest(at)entry=0x56b2b0ba6a68, altdest=altdest(at)entry=0x56b2b0ba6a68,
qc=qc(at)entry=0x7ffc452f04e0) at pquery.c:1277
#17 0x000056b2b02f210f in PortalRun (portal=portal(at)entry=0x56b2b0af24d0,
count=count(at)entry=9223372036854775807, isTopLevel=isTopLevel(at)entry=true,
run_once=run_once(at)entry=true, dest=dest(at)entry=0x56b2b0ba6a68,
altdest=altdest(at)entry=0x56b2b0ba6a68, qc=0x7ffc452f04e0) at pquery.c:791
#18 0x000056b2b02ee17d in exec_simple_query
(query_string=query_string(at)entry=0x56b2b0a5c9e0
"update ts_continuous_test SET val = 5 where time > 15 and time < 25;") at
postgres.c:1278
#19 0x000056b2b02f01a7 in PostgresMain (dbname=<optimized out>,
username=<optimized
out>) at postgres.c:4767
#20 0x000056b2b02e959e in BackendMain (startup_data=<optimized out>,
startup_data_len=<optimized out>) at backend_startup.c:105
#21 0x000056b2b023f955 in postmaster_child_launch (
child_type=child_type(at)entry=B_BACKEND,
startup_data=startup_data(at)entry=0x7ffc452f0714
"", startup_data_len=startup_data_len(at)entry=4,
client_sock=client_sock(at)entry=0x7ffc452f0750)

at launch_backend.c:277
#22 0x000056b2b024411e in BackendStartup
(client_sock=client_sock(at)entry=0x7ffc452f0750)
at postmaster.c:3593
#23 0x000056b2b02443a1 in ServerLoop () at postmaster.c:1674
#24 0x000056b2b0245a15 in PostmasterMain (argc=argc(at)entry=8,
argv=argv(at)entry=0x56b2b0a16860)
at postmaster.c:1372
#25 0x000056b2b0161207 in main (argc=8, argv=0x56b2b0a16860) at main.c:197

> There are three makeNode(ResultRelInfo), but they don't look anything
> out of the ordinary:
>
> C perhan: timescaledb 0$ git grep -C5 makeNode.ResultRelInfo
> src/copy.c- *
> src/copy.c- * WARNING. The dummy rangetable index is decremented by 1
> (unchecked)
> src/copy.c- * inside `ExecConstraints` so unless you want to have a
> overflow, keep it
> src/copy.c- * above zero. See `rt_fetch` in parsetree.h.
> src/copy.c- */
> src/copy.c: resultRelInfo = makeNode(ResultRelInfo);
> src/copy.c-
> src/copy.c-#if PG16_LT
> src/copy.c- ExecInitRangeTable(estate, pstate->p_rtable);
> src/copy.c-#else
> src/copy.c- Assert(pstate->p_rteperminfos != NULL);
> --
> src/nodes/chunk_dispatch/chunk_insert_state.c-create_chunk_result_relation_info(const
> ChunkDispatch *dispatch, Relation rel)
> src/nodes/chunk_dispatch/chunk_insert_state.c-{
> src/nodes/chunk_dispatch/chunk_insert_state.c- ResultRelInfo *rri;
> src/nodes/chunk_dispatch/chunk_insert_state.c- ResultRelInfo *rri_orig =
> dispatch->hypertable_result_rel_info;
> src/nodes/chunk_dispatch/chunk_insert_state.c- Index hyper_rti =
> rri_orig->ri_RangeTableIndex;
> src/nodes/chunk_dispatch/chunk_insert_state.c: rri =
> makeNode(ResultRelInfo);
> src/nodes/chunk_dispatch/chunk_insert_state.c-
> src/nodes/chunk_dispatch/chunk_insert_state.c- InitResultRelInfo(rri,
> rel, hyper_rti, NULL, dispatch->estate->es_instrument);
> src/nodes/chunk_dispatch/chunk_insert_state.c-
> src/nodes/chunk_dispatch/chunk_insert_state.c- /* Copy options from the
> main table's (hypertable's) result relation info */
> src/nodes/chunk_dispatch/chunk_insert_state.c- rri->ri_WithCheckOptions =
> rri_orig->ri_WithCheckOptions;
> --
> src/ts_catalog/catalog.c-extern TSDLLEXPORT ResultRelInfo *
> src/ts_catalog/catalog.c-ts_catalog_open_indexes(Relation heapRel)
> src/ts_catalog/catalog.c-{
> src/ts_catalog/catalog.c- ResultRelInfo *resultRelInfo;
> src/ts_catalog/catalog.c-
> src/ts_catalog/catalog.c: resultRelInfo = makeNode(ResultRelInfo);
> src/ts_catalog/catalog.c- resultRelInfo->ri_RangeTableIndex = 0; /*
> dummy */
> src/ts_catalog/catalog.c- resultRelInfo->ri_RelationDesc = heapRel;
> src/ts_catalog/catalog.c- resultRelInfo->ri_TrigDesc = NULL; /* we don't
> fire triggers */
> src/ts_catalog/catalog.c-
> src/ts_catalog/catalog.c- ExecOpenIndices(resultRelInfo, false);
>
>
> I didn't catch any other allocations that would depend on the size of
> ResultRelInfo in obvious ways.
>
>
>
> Oh, hmm, there's this bit which uses struct assignment into a stack
> element:
>
> tsl/src/compression/compression.c-1559- if
> (decompressor->indexstate->ri_NumIndices > 0)
> tsl/src/compression/compression.c-1560- {
> tsl/src/compression/compression.c:1561: ResultRelInfo indexstate_copy
> = *decompressor->indexstate;
> tsl/src/compression/compression.c-1562- Relation single_index_relation;
>
> I find this rather suspect.
>

Yes, I agree, trying to figure out other ways to deal with this piece of
code.

It is not possible to make a copy of the ResultRelInfo node here since
copyObject() does not support T_ResultRelInfo. Trying to use
CatalogOpenIndexes() causes another warning.

> --
> Álvaro Herrera PostgreSQL Developer —
> https://www.EnterpriseDB.com/
> "La espina, desde que nace, ya pincha" (Proverbio africano)
>
>
>

--
Best wishes,
Mats Kindahl, Timescale