Re: drop/truncate table sucks for large values of shared buffers

On Tue, Jun 30, 2015 at 11:00 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>
> On 30 June 2015 at 05:02, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>>
>> On Mon, Jun 29, 2015 at 7:18 PM, Simon Riggs <simon(at)2ndquadrant(dot)com>
wrote:
>> >
>> > On 28 June 2015 at 17:17, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> >>
>> > If lseek fails badly then SeqScans would give *silent* data loss,
which in my view is worse. Just added pages aren't the only thing we might
miss if lseek is badly wrong.
>> >
>>
>> So for the purpose of this patch, do we need to assume that
>> lseek can give us wrong size of file and we should add preventive
>> checks and other handling for the same?
>> I am okay to change that way, if we are going to have that as assumption
>> in out code wherever we are using it or will use it in-future, otherwise
>> we will end with some preventive checks which are actually not required.
>
>
> They're preventative checks. You always hope it is wasted effort.
>

I am not sure if Preventative checks (without the real need) are okay if
they
are not-cheap which could happen in this case. I think Validating
buffer-tag
would require rel or sys cache lookup.

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com