Re: Standard uuid vs. custom data type uuid_v1

On Thu, Jul 25, 2019 at 11:26:23AM +0200, Ancoron Luciferis wrote:
>Hi,
>
>I have finally found some time to implement a custom data type optimized
>for version 1 UUID's (timestamp, clock sequence, node):
>https://github.com/ancoron/pg-uuid-v1
>
>Some tests (using a few millions of rows) have shown the following
>results (when used as a primary key):
>
>COPY ... FROM: ~7.8x faster (from file - SSD)
>COPY ... TO  : ~1.5x faster (no where clause, sequential output)
>
>The best thing is that for INSERT's there is a very high chance of
>hitting the B-Tree "fastpath" because of the timestamp being the most
>significant part of the data type, which tends to be increasing.
>
>This also results in much lower "bloat", where the standard "uuid" type
>easily goes beyond 30%, the "uuid_v1" should be between 10 and 20%.
>
>Additionally, it also reveals the massive performance degrade I saw in
>my tests for standard UUID's:
>
>Initial 200 million rows: ~ 80k rows / second
>Additional 17 million rows: ~26k rows / second
>
>...and the new data type:
>Initial 200 million rows: ~ 623k rows / second
>Additional 17 million rows: ~618k rows / second
>

Presumably, the new data type is sorted in a way that eliminates/reduces
random I/O against the index. But maybe that's not the case - hard to
say, because the linked results don't say how the data files were
generated ...


regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services