On Fri, May 15, 2015 at 1:09 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
>> WALWriteLock contention is measurable on some workloads. In studying
>> the problem briefly, a couple of questions emerged:
>
>> 1. Doesn't it suck to rewrite an entire 8kB block every time, instead
>> of only the new bytes (and maybe a few bytes following that to spoil
>> any old data that might be there)?
>
> It does, but it's not clear how to avoid torn-write conditions without
> that.
Can you elaborate? I don't understand how repeatedly overwriting the
same bytes with themselves accomplishes anything at all.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company