Re: BUG #17619: AllocSizeIsValid violation in parallel hash join

On Thu, Sep 22, 2022 at 7:46 PM PG Bug reporting form
<noreply(at)postgresql(dot)org> wrote:
> (gdb) p size
> $2 = 1702125924

Thanks for the detailed report. Hmm. That size, on a little-endian
system, is equivalent to the byte sequence "date\0\0\0\0", which looks
pretty suspiciously like the inside of a tuple, and not its size. We
must have got out of sync somehow.

> Potentially interesting piece of the puzzle is that there are some long
> outliers in rhs.payload and rhs.source, but the rest of the columns have
> values that are exactly of avg_width bytes:
>
> # select log_len, count(*) from (select log(length(payload))::int as log_len
> from rhs) foo group by 1 order by 2 desc;
> log_len │ count
> ─────────┼────────
> 3 │ 840852
> 4 │ 77776
> 5 │ 8003
> 6 │ 1317
> 7 │ 20
> (5 rows)

So there are some strings up to order 10^7 in length in there. The
file format consists of chunks, with a special case for tuples that
don't fit in one chunk. Perhaps there is a bug in that logic. It is
exercised in our regression tests, but perhaps not enough. I'll try
to repro this from your clues.