Re: Buffer locking is special (hints, checksums, AIO writes)

Hello Andres,

12.03.2026 00:40, Andres Freund wrote:
> I pushed this and many of the later patches in the series. Here are updated
> versions of the remaining changes. The last two previously were one commit
> with "WIP" in the title. The first one has, I think, not had a lot of review -
> but it's also not a complicated change.

I've discovered that starting from 82467f627, the following query:
SET cpu_operator_cost = 1000;
CREATE TABLE t (i INT);
INSERT INTO T SELECT 1 FROM generate_series(1, 1000) a;
CREATE INDEX hi on t USING HASH (i);
DELETE FROM t WHERE i = 1;
DELETE FROM t WHERE i = 1;

triggers
TRAP: failed Assert("BufferIsValid(buffer)"), File: "bufmgr.c", Line: 497, PID: 3942058

#4  0x000079a60ae288ff in __GI_abort () at ./stdlib/abort.c:79
#5  0x00005a68d9343eef in ExceptionalCondition (conditionName=conditionName(at)entry=0x5a68d93ac27d "BufferIsValid(buffer)",
    fileName=fileName(at)entry=0x5a68d93c99ef "bufmgr.c", lineNumber=lineNumber(at)entry=497) at assert.c:65
#6  0x00005a68d91a18eb in GetPrivateRefCountEntry (do_move=true, buffer=<optimized out>) at bufmgr.c:497
#7  SharedBufferBeginSetHintBits (lockstate=<synthetic pointer>, buf_hdr=0x79e5febbbc40, buffer=<optimized out>)
    at bufmgr.c:6830
#8  BufferBeginSetHintBits (buffer=<optimized out>) at bufmgr.c:6931
#9  0x00005a68d8e3c862 in _hash_kill_items (scan=<optimized out>) at hashutil.c:603
#10 0x00005a68d8e3b7c3 in _hash_next (scan=0x5a68e735f938, dir=<optimized out>) at hashsearch.c:69
#11 0x00005a68d8e616ce in index_getnext_tid (scan=scan(at)entry=0x5a68e735f938, direction=direction(at)entry=ForwardScanDirection)
    at indexam.c:647
...
#25 0x00005a68d91eb4ad in exec_simple_query (query_string=0x5a68e7270120 "DELETE FROM t WHERE i = 1;") at postgres.c:1277
...

Could you please look at this?

Best regards,
Alexander