Jim C. Nasby wrote:
On Thu, Aug 17, 2006 at 12:41:57PM -0400, Matthew T. O'Connor wrote:
Would be fine by me, but I'm curious to see what the community has to
say. A few comments:
Autovacuum can cause unpredictable performance issues, that is if it
vacuums in the middle of a busy day and people don't want that, of
course they turn it off easy enough, but they might be surprised.
Anyone in that situation needs to be more hands-on with the database
anyway. I think the big target for autovac is beginners who otherwise
would bloat themselves silly (of course, it's also very useful far
beyond beginners, but by that time an admin should have some clue about
what they're doing).
Fair enough, also if we turn on the delay setting by default, it will
help address this.
And +1 on Rod's suggestion to make it more aggressive. I always drop the
scale factor to at least 0.2 and 0.1 (though 0.1 and 0.05 don't seem
unreasonable), and typically drop the thresholds to 200 and 100 (though
again, lower is probably warrented).
OK.
Actually, on a table small enough for the thresholds to kick in it's
going to be extremely fast to vacuum anyway, and the table is probably
either static or changing very rapidly. I'm wondering if maybe they
should just default to 0?
I assume you are suggesting that the base value be 0? Well for one
thing if the table doesn't have any rows that will result in constant
vacuuming of that table, so it needs to be greater than 0. For a small
table, say 100 rows, there usually isn'tn much performance impact if the
table if 50% dead space, so I think the base values you suggest are OK,
but they shouldn't be 0.
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