Re: Optimizing nbtree ScalarArrayOp execution, allowing multi-column ordered scans, skip scan - Mailing list pgsql-hackers

From Alexander Lakhin
Subject Re: Optimizing nbtree ScalarArrayOp execution, allowing multi-column ordered scans, skip scan
Date
Msg-id 6c68ac42-bbb5-8b24-103e-af0e279c536f@gmail.com
Whole thread Raw
In response to Re: Optimizing nbtree ScalarArrayOp execution, allowing multi-column ordered scans, skip scan  (Peter Geoghegan <pg@bowt.ie>)
Responses Re: Optimizing nbtree ScalarArrayOp execution, allowing multi-column ordered scans, skip scan
List pgsql-hackers
Hello Peter,

22.04.2024 20:59, Peter Geoghegan wrote:
>
> Pushed a fix like that just now. 

I'm sorry to bother you again, but I've come across another assertion
failure. Please try the following query (I use a clean "postgres" database,
just after initdb):
EXPLAIN SELECT conname
   FROM pg_constraint WHERE conname IN ('pkey', 'ID')
   ORDER BY conname DESC;

SELECT conname
   FROM pg_constraint WHERE conname IN ('pkey', 'ID')
   ORDER BY conname DESC;

It fails for me as below:
                                                      QUERY PLAN
--------------------------------------------------------------------------------------------------------------------
  Index Only Scan Backward using pg_constraint_conname_nsp_index on pg_constraint  (cost=0.14..4.18 rows=2 width=64)
    Index Cond: (conname = ANY ('{pkey,ID}'::name[]))
(2 rows)

server closed the connection unexpectedly
...
with the stack trace:
...
#5  0x000055a49f81148d in ExceptionalCondition (conditionName=0x55a49f8bb540 "ItemIdHasStorage(itemId)",
     fileName=0x55a49f8bb4a8 "../../../../src/include/storage/bufpage.h", lineNumber=355) at assert.c:66
#6  0x000055a49f0f2ddd in PageGetItem (page=0x7f97cbf17000 "", itemId=0x7f97cbf2f064)
     at ../../../../src/include/storage/bufpage.h:355
#7  0x000055a49f0f9367 in _bt_checkkeys_look_ahead (scan=0x55a4a0ac4548, pstate=0x7ffd1a103670, tupnatts=2,
     tupdesc=0x7f97cb5d7be8) at nbtutils.c:4105
#8  0x000055a49f0f8ac3 in _bt_checkkeys (scan=0x55a4a0ac4548, pstate=0x7ffd1a103670, arrayKeys=true,
     tuple=0x7f97cbf18890, tupnatts=2) at nbtutils.c:3612
#9  0x000055a49f0ebb4b in _bt_readpage (scan=0x55a4a0ac4548, dir=BackwardScanDirection, offnum=20, firstPage=true)
     at nbtsearch.c:1863
...
(gdb) f 7
#7  0x000055a49f0f9367 in _bt_checkkeys_look_ahead (scan=0x55a4a0ac4548, pstate=0x7ffd1a103670, tupnatts=2,
     tupdesc=0x7f97cb5d7be8) at nbtutils.c:4105
4105            ahead = (IndexTuple) PageGetItem(pstate->page,
(gdb) p aheadoffnum
$1 = 24596
(gdb) p pstate->offnum
$2 = 20
(gdb) p pstate->targetdistance
$3 = -24576

Best regards,
Alexander



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