Added to TODO: * Allow BEFORE INSERT triggers on views http://archives.postgresql.org/pgsql-general/2007-02/msg01466.php --------------------------------------------------------------------------- Tom Lane wrote: > "Karl O. Pinc" <kop@xxxxxxxx> writes: > > why can't I put a SELECT rule on a table? > > Because then it would be a view. > > As for $SUBJECT, the problem is that there will never be an insert into > a view --- not at the level of a physical insert attempt anyway --- and > thus there is nothing for a trigger to do. > > The reason there will never be an insertion trigger event is that we > reject any INSERT on a view that isn't rewritten (by an unconditional > DO INSTEAD rule) into something else. > > I recall a prior discussion about making it possible to use triggers on > views as a substitute for DO INSTEAD rules, by removing the rewrite-time > check and only erroring out if we actually get to the point of > attempting a physical insert. Then a BEFORE INSERT trigger could do > something appropriate with the data and return NULL to prevent the > error. This seems like a good idea because triggers often are much > easier to work with than rules --- eg, there's no problem with multiple > evaluations of volatile functions, even if you send the data to several > places. However, I'm not sure that the idea scales to cover updates and > deletes; with no concept of physical tuple identity (ctid) for the view > rows, it's not clear that you can write triggers that will reliably do > the right things. > > regards, tom lane > > ---------------------------(end of broadcast)--------------------------- > TIP 5: don't forget to increase your free space map settings -- Bruce Momjian <bruce@xxxxxxxxxx> http://momjian.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. +
