Re: Speedup of relation deletes during recovery

On Fri, Jun 22, 2018 at 5:41 AM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> On 2018-06-21 14:40:58 +0900, Michael Paquier wrote:
>> On Wed, Jun 20, 2018 at 08:43:11PM -0700, Andres Freund wrote:
>> > On 2018-06-18 11:13:47 -0700, Andres Freund wrote:
>> >> We could do that - but add_to_unowned_list() is actually a bottleneck in
>> >> other places during recovery too. We pretty much never (outside of
>> >> dropping relations / databases) close opened relations during recovery -
>> >> which is obviously problematic since nearly all of the entries are
>> >> unowned. I've come to the conclusion that we should have a global
>> >> variable that just disables adding anything to the global lists.
>> >
>> > On second thought: I think we should your approach in the back branches,
>> > and something like I'm suggesting in master once open.

I think we should take the hint in the comments and make it O(1)
anyway. See attached draft patch.

+ SMgrRelation *srels = NULL;

There seems to be no reason to initialise the variable to NULL in the
three places where you do that. It is always assigned a value before
use.

There is probably a way to share a bit more code among those three
places, but that sort of refactoring should be for later.

--
Thomas Munro
http://www.enterprisedb.com