Simon Riggs wrote:
One of us needs a coffee.
Clearly, I put the kettle on...
How does Transaction 4 have a RecentGlobalXmin of 2 in step (7), but at
step (9) the value of RecentGlobalXmin has gone backwards?
Looks like I mixed up the xids of the two transactions in steps 8 and 9.
Let's see if I got it right this time:
1. Transaction 1 begins in backend A
2. Transaction 2 begins in backend B, xmin = 1
3. Transaction 1 ends
4. Transaction 3 begins in backend C, xmin = 2
5. Backend C gets snapshot, TransactionXmin = 2, RecentGlobalXmin = 1
6. Transaction 2 ends.
7. Transaction 4 begins in backend A, gets snapshot TransactionXmin = 2,
RecentGlobalXmin = 2
8. Transaction 4 kills tuple, using its RecentGlobalxmin of 2
9. Transaction 3 splits the page, emits a delete xlog record, setting
latestRemovedXid to its RecentGlobalXmin of 1
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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