Helps me. Thanks for the clairification. On Wednesday 17 November 2004 06:49 am, Martijn van Oosterhout saith: > Just to clarify, there is a difference between OIDs and XIDs. Object > IDs (OID) are a system assigned field to every row that eventually > wraps around. If you don't use them in your application you'll hever > really have a problem. The only exception is that statements that > modify structures in the database (CREATE TRIGGER/TABLE/INDEX/etc) may > fail if you're unlucky enough to try them and it happens to be exactly > the OID of an existing thing of that type. > > Most people don't create 4 billion rows in their database so it's not > an issue. People who do are recommended to create their high churn > tables WITHOUT OIDS so they don't get used as fast. As an added bonus, > in recent versions you can actually save diskspace by not having them. > > Transaction IDs (XID) are a different story, they track transactions > and what is visible and what isn't. Transaction wraparound means that > rows will disappear when their transaction ID (which was considered in > the past) is now in the future. Since 7.2 this problem is avoided by > doing a database wide VACUUM (not necessarily FULL) at least once every > billion transactions. This is not an onerous requirement so people > don't run into this anymore. > > Before 7.2 you'd simply find your data missing one morning as the only > way to reset the XID was with an initdb. If you're still running a busy > database on something older than that, you *really* need to consider > taking appropriate measures! 7.2 is already fairly old now and all of > the major database destroying issues from then are now fixed. > > Hope this helps, > > On Tue, Nov 16, 2004 at 01:06:57PM +0200, Kostis Mentzelos wrote: > > I have read about oid wraparound in many messages but I don't understand > > when it happens and when it is dangerus for my tables. > > > > It affects developers that uses OIDS in their queryies? > > What about database and tables (not total or total) disappearences? > > > > Kostis. > > > > ---------------------------(end of broadcast)--------------------------- > > TIP 9: the planner will ignore your desire to choose an index scan if > > your joining column's datatypes do not match -- Quote: 28 "Without question, we need to disarm Saddam Hussein. He is a brutal, murderous dictator, leading an oppressive regime . . . He presents a particularly grievous threat because he is so consistently prone to miscalculation. . . . And now he is miscalculating America's response to his continued deceit and his consistent grasp for weapons of mass destruction. . . . So the threat of Saddam Hussein with weapons of mass destruction is real. . . ." -- Sen. John F. Kerry (D, MA), Jan. 23. 2003 Work: 1-336-372-6812 Cell: 1-336-363-4719 email: terry@xxxxxxxx ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to majordomo@xxxxxxxxxxxxxx
