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List:       postgresql-general
Subject:    Re: [HACKERS] Lockfree hashtables
From:       "Jonah H. Harris" <jonah.harris () gmail ! com>
Date:       2008-12-31 13:28:26
Message-ID: 36e682920812310528h1da15236l9d71d6e5db56f9db () mail ! gmail ! com
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On Wed, Dec 31, 2008 at 7:33 AM, Stephen R. van den Berg <srb@cuci.nl>wrote:

> The other day I bumped into some ideas about lockfree hashtables.
> Are these of any use in PostgreSQL?


Lock-free and wait-free algorithms have been used in various databases, but
most people tend to shy away from them because of their complexity,
difficulty to debug, and low-level portability issues.

I've used them in the past (lock-free hash tables and skip lists), and
they're pretty awesome if used properly, but the majority of PG's current
performance problems aren't generally found as part of our hash table
implementation (which I'm quite fond of actually).  FWIS, I think we'll look
more into this sometime in the future.

-- 
Jonah H. Harris, Senior DBA
myYearbook.com

[Attachment #3 (text/html)]

On Wed, Dec 31, 2008 at 7:33 AM, Stephen R. van den Berg <span dir="ltr">&lt;<a \
href="mailto:srb@cuci.nl">srb@cuci.nl</a>&gt;</span> wrote:<br><div \
class="gmail_quote"><blockquote class="gmail_quote" style="border-left: 1px solid \
rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> The other day I \
bumped into some ideas about lockfree hashtables.<br> Are these of any use in \
PostgreSQL?</blockquote><div><br>Lock-free and wait-free algorithms have been used in \
various databases, but most people tend to shy away from them because of their \
complexity, difficulty to debug, and low-level portability issues.<br> <br>I&#39;ve \
used them in the past (lock-free hash tables and skip lists), and they&#39;re pretty \
awesome if used properly, but the majority of PG&#39;s current performance problems \
aren&#39;t generally found as part of our hash table implementation (which I&#39;m \
quite fond of actually).&nbsp; FWIS, I think we&#39;ll look more into this sometime \
in the future.<br> </div></div><br>-- <br>Jonah H. Harris, Senior \
DBA<br>myYearbook.com<br><br>



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