Re: Parallel Inserts in CREATE TABLE AS

On Thu, May 27, 2021 at 12:19 PM houzj(dot)fnst(at)fujitsu(dot)com
<houzj(dot)fnst(at)fujitsu(dot)com> wrote:
> BTW, I checked my test results, I was testing INSERT INTO unlogged table.

What do you mean by "testing INSERT INTO"? Is it that you are testing
the timings for parallel inserts in INSERT INTO ... SELECT command? If
so, why should we test parallel inserts in the INSERT INTO ... SELECT
command here?

The way I test parallel inserts in CTAS is: Apply the latest v23 patch
set available at [1]. Run the data preparation sqls from [2]. Enable
timing and run the CTAS query from [3]. Run with 0, 2 and 4 workers
with leader participation on.

[1] - https://www.postgresql.org/message-id/CALj2ACXVWr1o%2BFZrkQt-2GvYfuMQeJjWohajmp62Wr6BU8Y4VA%40mail.gmail.com

[2]
DROP TABLE tenk1;
CREATE UNLOGGED TABLE tenk1(c1 bigint, c2 bigint, c3 name, c4 name, c5
name, c6 name, c7 name, c8 name, c9 name, c10 name, c11 name, c12
name, c13 name, c14 name, c15 name, c16 name, c17 name, c18 name);
INSERT INTO tenk1 values(generate_series(1,100000),
generate_series(1,10000000),
upper(substring(md5(random()::varchar),2,8)),
upper(substring(md5(random()::varchar),2,8)),
upper(substring(md5(random()::varchar),2,8)),
upper(substring(md5(random()::varchar),2,8)),
upper(substring(md5(random()::varchar),2,8)),
upper(substring(md5(random()::varchar),2,8)),
upper(substring(md5(random()::varchar),2,8)),
upper(substring(md5(random()::varchar),2,8)),
upper(substring(md5(random()::varchar),2,8)),
upper(substring(md5(random()::varchar),2,8)),
upper(substring(md5(random()::varchar),2,8)),
upper(substring(md5(random()::varchar),2,8)),
upper(substring(md5(random()::varchar),2,8)),
upper(substring(md5(random()::varchar),2,8)),
upper(substring(md5(random()::varchar),2,8)),
upper(substring(md5(random()::varchar),2,8)));

[3]
EXPLAIN ANALYZE VERBOSE CREATE TABLE test AS SELECT * FROM tenk1;

With Regards,
Bharath Rupireddy.
EnterpriseDB: http://www.enterprisedb.com