On Tue, 10 Aug 2021 at 20:53, Yura Sokolov <y.soko...@postgrespro.ru> wrote: > EXPLAIN shows that there are 2604186278 rows in all partitions, but > planner > thinks there will be only 200 unique rows after group by. Looks like we > was > mistaken.
This looks unrelated. Looks like the planner used DEFAULT_NUM_DISTINCT. > /* now set size */ > tb->size = size; > > if (tb->size == SH_MAX_SIZE) > tb->sizemask = 0; > else > tb->sizemask = tb->size - 1; Ouch. That's not great. > /* now set size */ > tb->size = size; > tb->sizemask = (uint32)(size - 1); That fix seems fine. > I went to check SH_GROW and.... It is `SH_GROW(SH_TYPE *tb, uint32 > newsize)` > :-((( > Therefore when `tb->size == SH_MAX_SIZE/2` and we call `SH_GROW(tb, > tb->size * 2)`, > then SH_GROW(tb, 0) is called due to truncation. > And SH_COMPUTE_PARAMETERS is also accepts `uint32 newsize`. Yeah. Agreed. I don't see anything wrong with your fix for that. I'm surprised nobody has hit this before. I guess having that many groups is not common. Annoyingly this just missed the window for being fixed in the minor releases going out soon. We'll need to wait a few days before patching. David
