On 26/05/10 21:35, Josh Berkus wrote:
On 5/25/10 10:04 PM, Heikki Linnakangas wrote:
On 25/05/10 23:56, Josh Berkus wrote:
Do we get a bit in the visibility map for a page which has aborted
transaction rows on it?
If there's a tuple with an aborted xmin on a page, the bit in the
visibility map is not set. A tuple with aborted xmax doesn't matter.
Then it seems like pages in the visibility map, at least, would not need
to be vacuumed or frozen. Do pages persist in the visibility map
indefinitely?
In theory, until any tuple on the page is inserted/updated/deleted
again. However, we've been operating on the assumption that it's always
safe to clear any bit in the visibility map, without affecting
correctness. I would not like to give up that assumption, it makes life
easier.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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