Re: BUG #18806: When enable_rartitionwise_join is set to ON, the database shuts down abnormally

Tender Wang <tndrwang(at)gmail(dot)com> 于2025年2月12日周三 17:48写道：

>
>
> Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> 于2025年2月12日周三 15:38写道：
>
>> On Wed, 2025-02-12 at 07:01 +0000, PG Bug reporting form wrote:
>> > PostgreSQL version: 17.2
>> > Operating system: CentOS Linux release 7.9.2009 (Core)
>> > Description:
>> >
>> > After upgrading PG17.2, testing found that when
>> enable_rartitionwise_join is
>> > set to ON, when executing a query, if the main query and subquery have
>> the
>> > same table, the query will report an error.
>> >
>> > The database log shows the following error:
>> > LOG: server process (PID 24796) was terminated by signal 6: Aborted
>> > DETAIL: Failed process was running: select * from test t join orders o
>> on
>> > t.order_id =o.order_id where t.order_id in (select order_id from
>> orders);
>> > LOG: terminating any other active server processes
>>
>> That is a crash that may well indicate a PostgreSQL bug.
>>
>> However, without a way to reproduce the behavior, we won't be able to fix
>> the problem. Try to come up with a self-contained test case. It would
>> also be interesting to know which PostgreSQL extensions are present.
>>
>>
> I can reproduce this crash on HEAD.
>
> postgres=# create table test(order_id int, name varchar);
> create table orders(order_id int, name char(10)) partition by hash
> (order_id);
> CREATE TABLE
> CREATE TABLE
> postgres=# set enable_partitionwise_join = on;
> SET
> postgres=# create table orders_p1 partition of orders for values with (
> modulus 32, remainder 0);
> CREATE TABLE
> postgres=# explain select * from test t join orders o on
> t.order_id =o.order_id where t.order_id in (select order_id from orders);
> server closed the connection unexpectedly
> This probably means the server terminated abnormally
> before or while processing the request.
> The connection to the server was lost. Attempting reset: Succeeded.
>
>
I debug this crash, I found this crash was related with below commit:
commit 5278d0a2e870c61f9374a7796b90e6f9f6a73638
Author: Amit Langote <amitlan(at)postgresql(dot)org>
Date: Mon Mar 25 12:02:40 2024 +0900

Reduce memory used by partitionwise joins

the joinlist in this query is 1,2,5
1 means table t
2 means table orders
5 also means table orders, which subquery is pulled up.
When we create join rel for (2,5), then wen enter try_partitionwise_join().
In this func, we call build_child_join_sjinfo() to build SpecialJoinInfo
for child.
In build_child_join_sjinfo(), we use memcpy(), I think we should use
copyObject().
Otherwise, the parent_sjinfo will be freed, for example, after
call free_child_join_sjinfo(),
the parent_sjinfo min_lefthand looks like as below:

(gdb) p *parent_sjinfo->min_lefthand
$7 = {type = 3951489872, nwords = 21994, words = 0x55eaeb8696b0}

The above bitmap is invalid, so trigger the Assert(bms_is_valid_set(a));

Attached patch is my fix. Any thoughts?

--
Thanks,
Tender Wang