On Fri, 2008-09-19 at 17:47 -0400, Tom Lane wrote: > Greg Smith <[EMAIL PROTECTED]> writes: > > On Fri, 19 Sep 2008, Greg Stark wrote: > >> This is a good example of why running with assertions enabled on > >> production > >> might not be a good idea. But it's also a good example of why we should do > >> our performance testing with assertions enabled if we can do it without > >> invalidating the results. > > > The performance impact of assertions is large enough that I don't think > > that goal is practical. > > Well, there are certain things that --enable-cassert turns on that are > outrageously expensive; notably CLOBBER_FREED_MEMORY and > MEMORY_CONTEXT_CHECKING. It wouldn't be too unreasonable to decouple > those things somehow (with a means more accessible than editing > pg_config_manual.h).
That's mostly what I'm hoping for. If we call the CLOBBER checks as class 3, all current Asserts as class 2 then we can invent a class 1 of specifically lightweight checks (only). We can then have --enable-cassert=X rather than just y or n > I don't think anyone knows what the performance impact of just the > regular Asserts is; it's been too long since these other things were > stuck in there. Agreed. If we had a system in place, we would slowly move towards using it. It wouldn't happen overnight, but it would help. Many more people might be persuaded to be early adopters if there was an extra mode in place to catch problems. My thinking was that I want to put lots of checks into Hot Standby to prove it all works, but in places where I don't think they're really needed. An example of a current set of checks we do, that may not be needed are the tests for HeapTupleInvisible in HeapTupleSatisfiesUpdate(). Almost every time we do a TransactionIdIsInProgress() to see if the heap tuple is invisible. If it is we throw an ERROR. But we already did that earlier. Now I've never seen that ERROR reported anywhere, so I'm thinking that I'd like to downgrade that somehow, yet still retain the ability to check it when things go strange. There are a few other examples. -- Simon Riggs www.2ndQuadrant.com PostgreSQL Training, Services and Support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
