Re: init_sequence spill to hash table

Hi,

On 2013-11-13 22:55:43 +1300, David Rowley wrote:
> Here http://www.postgresql.org/message-id/24278.1352922571@sss.pgh.pa.us there
> was some talk about init_sequence being a bottleneck when many sequences
> are used in a single backend.
>
> The attached I think implements what was talked about in the above link
> which for me seems to double the speed of a currval() loop over 30000
> sequences. It goes from about 7 seconds to 3.5 on my laptop.

I think it'd be a better idea to integrate the sequence caching logic
into the relcache. There's a comment about it:
* (We can't
* rely on the relcache, since it's only, well, a cache, and may decide to
* discard entries.)
but that's not really accurate anymore. We have the infrastructure for
keeping values across resets and we don't discard entries.

Since we already do a relcache lookup for every sequence manipulation
(c.f. init_sequence()) relying on it won't increase, but rather decrease
the overhead.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
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