From: | Richard Guo <guofenglinux(at)gmail(dot)com> |
---|---|
To: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Wrong results from Parallel Hash Full Join |
Date: | 2023-04-12 11:35:53 |
Message-ID: | CAMbWs48Nde1Mv=BJv6_vXmRKHMuHZm2Q_g4F6Z3_pn+3EV6BGQ@mail.gmail.com |
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Lists: | pgsql-hackers |
I came across $subject and reduced the repro query as below.
create table a (i int);
create table b (i int);
insert into a values (1);
insert into b values (2);
update b set i = 2;
set min_parallel_table_scan_size to 0;
set parallel_tuple_cost to 0;
set parallel_setup_cost to 0;
# explain (costs off) select * from a full join b on a.i = b.i;
QUERY PLAN
------------------------------------------
Gather
Workers Planned: 2
-> Parallel Hash Full Join
Hash Cond: (a.i = b.i)
-> Parallel Seq Scan on a
-> Parallel Hash
-> Parallel Seq Scan on b
(7 rows)
# select * from a full join b on a.i = b.i;
i | i
---+---
1 |
(1 row)
Tuple (NULL, 2) is missing from the results.
Thanks
Richard
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