Re: pgbench - allow to create partitioned tables

From: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
To: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Cc: Asif Rehman <asifr(dot)rehman(at)gmail(dot)com>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: pgbench - allow to create partitioned tables
Date: 2019-09-21 07:48:31
Message-ID: alpine.DEB.2.21.1909210813010.21682@lancre
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Hello Amit,

> Yes, this code is correct. I am not sure if you understood the point,
> so let me try again. I am bothered about below code in the patch:
> + /* only print partitioning information if some partitioning was detected */
> + if (partition_method != PART_NONE)
> This is the only place now where we check 'whether there are any
> partitions' differently. I am suggesting to make this similar to
> other checks (if (partitions > 0)).

As I said somewhere up thread, you can have a partitioned table with zero
partitions, and it works fine (yep! the update just does not do anything…)
so partitions > 0 is not a good way to know whether there is a partitioned
table when running a bench. It is a good way for initialization, though,
because we are creating them.

sh> pgbench -i --partitions=1
sh> psql -c 'DROP TABLE pgbench_accounts_1'
sh> pgbench -T 10
transaction type: <builtin: TPC-B (sort of)>
scaling factor: 1
partition method: hash
partitions: 0
query mode: simple
number of clients: 1
number of threads: 1
duration: 10 s
number of transactions actually processed: 2314
latency average = 4.323 ms
tps = 231.297122 (including connections establishing)
tps = 231.549125 (excluding connections establishing)

As postgres does not break, there is no good reason to forbid it.

> [...] Sure, even in that case your older version of pgbench will be able
> to detect by below code [...] "unexpected partition method: " [...].

Yes, that is what I was saying.

> Hmm, you have just written what each part of the query is doing which I
> think one can identify if we write some general comment as I have in the
> patch to explain the overall intent. Even if we write what each part of
> the statement is doing, the comment explaining overall intent is
> required.

There was some comments.

> I personally don't like writing a comment for each sub-part of the query
> as that makes reading the query difficult. See the patch sent by me in
> my previous email.

I did not notice there was an attachment.

> I have done that in some of the cases in the patch attached by me in
> my last email. Have you looked at those changes?

Nope, as I was not expected one.

> Try to make those changes in the next version unless you see something
> wrong is written in comments.

I incorporated most of them, although I made them terser, and fixed them
when inaccurate.

I did not buy moving the condition inside the fillfactor function.

See attached v14.


Attachment Content-Type Size
pgbench-init-partitioned-14.patch text/x-diff 13.8 KB

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