Relaxin wrote: > I'm a consultant for a large company and they are looking at a database to > use. > > I made the suggestion about going with Postgresql. > > I told him about it's MVCC design, he liked that ideal, but wanted to know > exactly HOW did it handle the multiple versions of records. He's concerned > because he was burn very early on by another database that was MVCC (won't > mention any names) and his system became corrupt. That database has since > improved and fixed all of their problems. > > But the question is, how does Postgresql handle the multiple versions? > How does it handle the records BEFORE they are committed and how does it > handle the records AFTER they are committed that allows different users to > possible have a different view of the data and indexes. And also how does > the transactional part of the system place a role?
Each record has a transction id of creation and an expire transaction id. When you add a record, you put your xid on the old record and create a new one. No one has reported any corruption problems with our database for a long time, so you should be fine. If you want details, see the developers web page and see my internals presentation --- it has a diagram showing old/new rows and their visibility to a single transaction. -- Bruce Momjian | http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org
