Hm, looks like it could speed up PostgreSQL recovery, but is it safe?
On 02/11/2019 07:25 PM, Arthur Zakirov wrote:
Hello hackers,
Grigory noticed that one of our utilities has very slow performance
when xlogreader reads zlib archives. We found out that xlogreader
sometimes reads a WAL file block twice.
zlib has slow performance when you read an archive not in sequential
order. I think reading a block twice in same position isn't
sequential, because gzread() moves current position forward and next
call gzseek() to the same position moves it back.
It seems that the attached patch solves the issue. I think when reqLen
== state->readLen the requested block already is in the xlogreader's
buffer.
What do you think?
--
Grigory Smolkin
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
