O Owen Jacobson έγραψε στις Feb 24, 2006 : > Achilleus Mantzios wrote: > > > O Tom Lane έγραψε στις Feb 24, 2006 : > > > > > By definition, an AFTER trigger is too late to change what was > > > stored. Use a BEFORE trigger. > > > > Too late if someone wants to store it. > > I wanna store the intented original values, thats why i use > > AFTER trigger. > > But i would like to alter what a final AFTER trigger would see. > > > > I'll elabarote a little. > > > > An update happens. > > The row is stored. > > An after trigger is fired that alters some NEW columns > > (nullifies them), aiming for a subsequent trigger > > to see the altered results . > > > > It should be something like a pointer to a HeapTuple, (right?), > > so that would be feasible i suppose. > > > > I would not even make a post if it was something that trivial. > > > > I hope you get my point. > > Your real problem is that the "subsequent" trigger has behaviour you don't > like. That's what you should be fixing. If dbmirror has no way to exclude > specific tables from mirroring, take it up with them as a feature request, or > patch dbmirror to work how you want it to. > > AFTER triggers *must* receive the row that was actually > inserted/updated/deleted. If they could receive a "modified" row that didn't > reflect what was actually in the database, all sorts of useful trigger-based > logging and replication patterns wouldn't work, and there's really no other > way to implement them. See also Tom Lane's other message for further > implications of being able to modify the rows seen by AFTER triggers. >
As i have explained my dbmirror is FK null values gnostic(=aware) already as we speak. It normaly mirrors father rows according to certain criteria. (And the fathers of them and so on). Replication is done over UUCP over 5$/min satelite connections, so replicating just the right data for a slave is critically important. So nullifying a value just before the dbmirror trigger would do exactly the right thing (for me) Now implementing the "nullification on demand" feature in dbmirror means more work when i migrate to 8.x, i have severly modified dbmirror to do many things, and i thought it was time to stop! > I'd also be hesitant to write triggers that have to execute in a specific > order. Meaning that would hurt portability? Most people need features rathen than the relief to know they can migrate to another database (which they probably never will) > Back to AFTER trigger changing values issue, i think things are not so dramatic if FK triggers could just be fired first. Anyway i'll modify dbmirror again. Oh BTW, There is a patch for DBMirror.pl (which steven hasnt yet fully reviewed) that solves the previous performance problems. > ---------------------------(end of broadcast)--------------------------- > TIP 5: don't forget to increase your free space map settings > -- -Achilleus ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
