Re: pgbench - allow to create partitioned tables

On Wed, Sep 11, 2019 at 6:08 PM Fabien COELHO <coelho@cri.ensmp.fr> wrote:
>
>

I would like to take inputs from others as well for the display part
of this patch.  After this patch, for a simple-update pgbench test,
the changed output will be as follows (note: partition method and
partitions):
pgbench.exe -c 4 -j 4 -T 10 -N postgres
starting vacuum...end.
transaction type: <builtin: simple update>
scaling factor: 1
partition method: hash
partitions: 3
query mode: simple
number of clients: 4
number of threads: 4
duration: 10 s
number of transactions actually processed: 14563
latency average = 2.749 ms
tps = 1454.899150 (including connections establishing)
tps = 1466.689412 (excluding connections establishing)

What do others think about this?  This will be the case when the user
has used --partitions option in pgbench, otherwise, it won't change.

>
> > + case 11: /* partitions */
> > + initialization_option_set = true;
> > + partitions = atoi(optarg);
> > + if (partitions < 0)
> > + {
> > + fprintf(stderr, "invalid number of partitions: \"%s\"\n",
> > + optarg);
> > + exit(1);
> > + }
> > + break;
> >
> > Is there a reason why we treat "partitions = 0" as a valid value?
>
> Yes. It is an explicit "do not create partitioned tables", which differ
> from 1 which says "create a partitionned table with just one partition".
>

Why would anyone want to use --partitions option in the first case
("do not create partitioned tables")?

>
> > I think we should print the information about partitions in
> > printResults.  It can help users while analyzing results.
>
> Hmmm. Why not, with some hocus-pocus to get the information out of
> pg_catalog, and trying to fail gracefully so that if pgbench is run
> against a no partitioning-support version.
>

+ res = PQexec(con,
+ "select p.partstrat, count(*) "
+ "from pg_catalog.pg_class as c "
+ "left join pg_catalog.pg_partitioned_table as p on (p.partrelid = c.oid) "
+ "left join pg_catalog.pg_inherits as i on (c.oid = i.inhparent) "
+ "where c.relname = 'pgbench_accounts' "
+ "group by 1, c.oid");

Can't we write this query with inner join instead of left join?  What
additional purpose you are trying to serve by using left join?

> > *
> > +enum { PART_NONE, PART_RANGE, PART_HASH }
> > + partition_method = PART_NONE;
> > +
> >
> > I think it is better to follow the style of QueryMode enum by using
> > typedef here, that will make look code in sync with nearby code.
>
> Hmmm. Why not. This means inventing a used-once type name for
> partition_method. My great creativity lead to partition_method_t.
>

+partition_method_t partition_method = PART_NONE;

It is better to make this static.


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