Horton

Re: [patch]HashJoin crash

Justin Pryzby <pryzby@telsasoft.com>

View thread View on postgr.es
From: Justin Pryzby <pryzby@telsasoft.com>
To: Zhang Mingli <zmlpostgres@gmail.com>
Cc: pgsql-hackers@lists.postgresql.org, Tom Lane <tgl@sss.pgh.pa.us>
Date: 2022-08-13T19:17:46Z
Lists: pgsql-hackers 
+ Tom Lane

On Fri, Aug 12, 2022 at 11:05:06PM +0800, Zhang Mingli wrote:
> I got a coredump when using hash join on a Postgres derived Database(Greenplum DB).
> And I find a way to reproduce it on Postgres.
> 
> Root cause:
> 
> In ExecChooseHashTableSize(), commit b154ee63bb uses func pg_nextpower2_size_t
> whose param must not be 0.
> 
> sbuckets = pg_nextpower2_size_t(hash_table_bytes / bucket_size);
> 
> There is a potential risk that hash_table_bytes < bucket_size in some corner cases.
> 
> Reproduce sql:

Commits

  1. Avoid misbehavior when hash_table_bytes < bucket_size.

  2. Get rid of artificial restriction on hash table sizes on Windows.