Re: Do we really need to switch to per-tuple memory context in ATRewriteTable() when Table Rewrite is not happening

On Wed, Jan 3, 2018 at 7:25 PM, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
> Ashutosh Sharma wrote:
>
>> I am basically talking about the following lines of code in
>> ATRewriteTable() function.
>>
>> /*
>> * Switch to per-tuple memory context and reset it for each tuple
>> * produced, so we don't leak memory.
>> */
>> oldCxt = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
>
> Perhaps a memory context switch is so cheap that adding a branch to
> verify whether it's needed is more expensive than just doing it all the
> time. You could prove me wrong by measuring it.
>

might be...I'm not sure about the cost of context switching. As you
said, it is quite possible that adding a check to verify whether
switching is required or not could be more expensive than doing the
context switching itself.

--
With Regards,
Ashutosh Sharma
EnterpriseDB:http://www.enterprisedb.com

> --
> Álvaro Herrera https://www.2ndQuadrant.com/
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