Re: Remove redundant MemoryContextSwith in BeginCopyFrom

Japin Li <japinli@hotmail.com>

From: Japin Li <japinli@hotmail.com>

To: Tom Lane <tgl@sss.pgh.pa.us>

Cc: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>

Date: 2022-01-20T00:44:17Z

Lists: pgsql-hackers

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Remove redundant memory context switches in BeginCopyFrom().
- 89f059bdf52c 15.0 landed

On Thu, 20 Jan 2022 at 00:38, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com> writes:
>> +1. It looks like a thinko from c532d15d. There's no code in between,
>> so switching to oldcontext doesn't make sense.
>
> Agreed.
>
>> I think we also need to remove MemoryContextSwitchTo(oldcontext); at
>> the end of BeginCopyTo in copyto.c, because we are not changing memory
>> contexts in between.
>
> Hmm, I think it'd be a better idea to remove the one in the middle of
> BeginCopyTo.  The code after that is still doing setup of the cstate,
> so the early switch back looks to me like trouble waiting to happen.
>

Agreed

I see you have already push this patch on master (89f059bdf52), why not
remove MemoryContextSwitchTo in the middle of BeginCopyTo in this commit?

-- 
Regrads,
Japin Li.
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