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On May 23, 2015 01:48:11 PM David G. Johnston wrote: > On Sat, May 23, 2015 at 1:34 PM, Ravi Krishna <sravikrishna3@xxxxxxxxx> > > wrote: > > Is it true that PG does not log undo information, only redo. If true, > > then how does it bring a database back to consistent state during > > crash recovery. Just curious. > > What does "undo" mean? > > David J.
Methinks rolling back the changes that transactions which got interrupted by the crash scribbled onto the data file. It's an Oracleism where not-consolidated data is kept in undo- and redo datafiles.
While I roughly understand Postgres' MVCC I don't feel qualified to answer Ravi's question :-) |
