Re: Undelete a deleted row

Art S. Kagel wrote: > Pachiano, Vince wrote: > > At the risk of starting a new thread, I have this question to > > ask about the lack of an undelete: > > > > "If not, why not?" > > Certainly not because it makes life more interesting. Mostly because > with the current structure of the database on disk it would be > impossible after only a few seconds as other records would be inserted > over the vacated data space. It is possible to extract the deleted > pre-images from the logical log files using the rlog utility and > manually re-insert the rows. A few folk have braved insanity to > attempt this as a last resort. More importantly, because things like ANSI SQL standard and the TPPC benchmarks (TPC-C, TPC-D, etc) require changes to be permanent once committed (the ACID properties - especially D for durability). An undelete operation breaks the durability requirement. Further, even if you could undo some change, you could not undo all the changes that relied upon the fact that the data had been deleted - life in a big database goes on after the demise of any row, and queries and inserts can be affected by the fact that the row was deleted. So, recovering a deleted record could distort a lot of other operational data which was based on the fact that the row was deleted. -- Jonathan Leffler (jleffler@informix.com, jleffler@earthlink.net) Guardian of DBD::Informix v0.60 -- see http://www.perl.com/CPAN #include <disclaimer.h>