| From: | Greg Stark <stark(at)mit(dot)edu> |
|---|---|
| To: | Kevin Grittner <kgrittn(at)ymail(dot)com> |
| Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, Merlin Moncure <mmoncure(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Limiting setting of hint bits by read-only queries; vacuum_delay |
| Date: | 2013-03-25 22:57:43 |
| Message-ID: | CAM-w4HMoCsvKQhaJwOzvdY=x30hkYNaqj3vKwcmg-YmKZRF+Ug@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, Mar 25, 2013 at 9:53 PM, Kevin Grittner <kgrittn(at)ymail(dot)com> wrote:
> That would make it harder to construct a degenerate case
I don't think it's hard at all. It's the same as the case Simon wants
to solve except that the cost is incurred in a different way. Imagine
a system where there's a huge data load to a table which is then
read-only for an OLTP system. Until vacuum comes along -- and it may
never since the table never sees deletes or updates -- every
transaction needs to do a clog lookup for every tuple it sees. That
means a significant cpu slowdown for every row lookup forever more. To
save a one-time i/o cost.
--
greg
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