Re: [GENERAL] Autovacuum Improvements

In an attempt to throw the authorities off his trail, alvherre@commandprompt.com (Alvaro Herrera) transmitted:
> Simon Riggs wrote:
>
>> Some feedback from initial testing is that 2 queues probably isn't
>> enough. If you have tables with 100s of blocks and tables with
>> millions of blocks, the tables in the mid-range still lose out. So
>> I'm thinking that a design with 3 queues based upon size ranges,
>> plus the idea that when a queue is empty it will scan for tables
>> slightly above/below its normal range.
>
> Yeah, eventually it occurred to me the fact that as soon as you have
> 2 queues, you may as well want to have 3 or in fact any number.
> Which in my proposal is very easily achieved.

Adding an extra attribute to reflect a different ordering or a
different policy allows having as many queues in one queue table as
you might need.

>> Alvaro, have you completed your design?
>
> No, I haven't, and the part that's missing is precisely the queues
> stuff.  I think I've been delaying posting it for too long, and that
> is harmful because it makes other people waste time thinking on
> issues that I may already have resolved, and delays the bashing that
> yet others will surely inflict on my proposal, which is never a good
> thing ;-) So maybe I'll put in a stub about the "queues" stuff and
> see how people like the whole thing.

Seems like a good idea to me.

Implementing multiple queues amounts to having different worker
processes/threads that operate on the queue table using varying
policies.
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