Re: Parallel Inserts in CREATE TABLE AS

On Sat, Dec 26, 2020 at 9:20 PM vignesh C <vignesh21(at)gmail(dot)com> wrote:
> +-- parallel inserts must occur
> +select explain_pictas(
> +'create table parallel_write as select length(stringu1) from tenk1;');
> +select count(*) from parallel_write;
> +drop table parallel_write;
>
> We can change comment "parallel inserts must occur" like "parallel
> insert must be selected for CTAS on normal table"
>
> +-- parallel inserts must occur
> +select explain_pictas(
> +'create unlogged table parallel_write as select length(stringu1) from tenk1;');
> +select count(*) from parallel_write;
> +drop table parallel_write;
>
> We can change comment "parallel inserts must occur" like "parallel
> insert must be selected for CTAS on unlogged table"
> Similar comment need to be handled in other places also.

I think the existing comments look fine. The info like table type and
the Query CTAS or CMV is visible by looking at the test case. What I
wanted from the comments is whether we support parallel inserts or not
and if not why so that it will be easy to read. I tried to keep it as
succinctly as possible.

> If possible try to make a common function for both and use.

Yes you are right. The function explain_pictas is the same as
explain_parallel_append from partition_prune.sql. It's a test
function, and I also see that we have serial_schedule and
parallel_schedule which means that these sql files can run in any
order. I'm not quite sure whether we can have it in a common test sql
file and use it across other tests sql files. AFAICS, I didn't find
any function being used in such a manner. Thoughts?

> + if (intoclausestr && OidIsValid(objectid))
> + fpes->objectid = objectid;
> + else
> + fpes->objectid = InvalidOid;
> Here OidIsValid(objectid) check is not required intoclausestr will be
> set only if OidIsValid.

Removed the OidIsValid check in the latest v16 patch set posted
upthread. Please have a look.

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