Re: [HACKERS] Block level parallel vacuum

On Fri, Oct 4, 2019 at 4:18 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Wed, Oct 2, 2019 at 7:29 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>>

Few more comments:
---------------------------------
1. Caurrently parallel vacuum is allowed for temporary relations
which is wrong. It leads to below error:

postgres=# create temporary table tmp_t1(c1 int, c2 char(10));
CREATE TABLE
postgres=# create index idx_tmp_t1 on tmp_t1(c1);
CREATE INDEX
postgres=# create index idx1_tmp_t1 on tmp_t1(c2);
CREATE INDEX
postgres=# insert into tmp_t1 values(generate_series(1,10000),'aaaa');
INSERT 0 10000
postgres=# delete from tmp_t1 where c1 > 5000;
DELETE 5000
postgres=# vacuum (parallel 2) tmp_t1;
ERROR: cannot access temporary tables during a parallel operation
CONTEXT: parallel worker

The parallel vacuum shouldn't be allowed for temporary relations.

2.
--- a/doc/src/sgml/ref/vacuum.sgml
+++ b/doc/src/sgml/ref/vacuum.sgml
@@ -34,6 +34,7 @@ VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [
<replaceable class="paramet
SKIP_LOCKED [ <replaceable class="parameter">boolean</replaceable> ]
INDEX_CLEANUP [ <replaceable
class="parameter">boolean</replaceable> ]
TRUNCATE [ <replaceable class="parameter">boolean</replaceable> ]
+ PARALLEL [ <replaceable
class="parameter">integer</replaceable> ]

Now, if the user gives a command like Vacuum (analyze, parallel)
<table_name>; it is not very obvious that a parallel option will be
only used for vacuum purposes but not for analyze. I think we can add
a note in the docs to mention this explicitly. This can avoid any
confusion.

--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com