Ühel kenal päeval, K, 2006-08-23 kell 05:23, kirjutas Gregory Stark: > With all this code to handle ignoring vacuum transactions in calculating the > global xmin it just occurred to me to wonder: Does lazy vacuum need a > transaction at all? It doesn't do the tuple moving tricks with xvac that > vacuum full does so does lazy vacuum's xid ever make it into tables? Couldn't > it just use GetTopTransactionId instead of its own xid? Would this cause any > problems?
When I asked the same question, I was told that a lot of core functionality vacuum uses needs to be in transaction. I guess bad things can happen, if some other backend ends a transaction you claim to be in. And it is not so much about what ends up in tables, but about what other backends think. BTW, I think that CONCURRENT CREATE INDEX should be modified to use long transactions which actually build the index and are ignored by vacuum and short ones which write data to system tables and are not ignored. That way we have one less obstacle for keeping high-update tables in shape. > -- ---------------- Hannu Krosing Database Architect Skype Technologies OÜ Akadeemia tee 21 F, Tallinn, 12618, Estonia Skype me: callto:hkrosing Get Skype for free: http://www.skype.com ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
