RE: exchange thread?

I believe they are called exchange iterator, but whatever. (I'll talk it through from an XPS standpoint) The query plan that actually runs (let's say for a hash join) looks something like: scan tab1, build hash table scan tab2, probe hash table project insert (if you happen to be dumping them into a table) As expressed it really looks like: scan scan hash join project insert Each of these operations is executed by a set of threads, to communicate data between these threads, there is a set of exhange iterators. So if you look at this plan running (onstat -g xmp - as summarized by my lovely script) you might see - well actually I have something running right now which is an unload to a table - that goes as: scan convert write You can see how the exhange iterators surround the basic operation: insert into tab1_x select * from tab1 scan 3 tab1 Operation Phase Threads Rows scan next 32 1017747479 xucnv 2 Operation Phase Threads Rows xchg next 16 0 xucnv next 16 1017378554 xchg open 16 1405093 xuwrite 1 Operation Phase Threads Rows xchg next 12 0 xuwrite open 12 1017160411 xchg open 12 0 cheers j. > -----Original Message----- > From: sudhakar [mailto:k_sudhak@rediffmail.com] > Sent: Friday, February 02, 2001 7:30 AM > To: informix-list@iiug.org > Subject: exchange thread? > > > hello, > can anyone explain me > what is an exchange thread ? > and the concept behind it. > bye > sudhakar > > -- > Posted via CNET Help.com > http://www.help.com/ >