Re: [PATCHES] [HACKERS] HOT WIP Patch - version 2
Bruce Momjian [EMAIL PROTECTED] writes: Pavan Deolasee wrote: When following a HOT-update chain from the index fetch, if we notice that the root tuple is dead and it is HOT-updated, we try to prune the chain to the smallest possible length. To do that, the share lock is upgraded to an exclusive lock and the tuple chain is followed till we find a live/recently-dead tuple. At that point, the root t_ctid is made point to that tuple. In order I assume you meant recently-dead here, rather than live/recently-dead, because we aren't going to change live ctids, right? Recently dead means still live to somebody, so those tids better not change either. But I don't think that's what he meant. I'm more worried about the deadlock possibilities inherent in trying to upgrade a buffer lock. We do not have deadlock detection for LWLocks. regards, tom lane ---(end of broadcast)--- TIP 4: Have you searched our list archives? http://archives.postgresql.org
Re: [PATCHES] [HACKERS] HOT WIP Patch - version 2
Tom Lane wrote: Bruce Momjian [EMAIL PROTECTED] writes: Pavan Deolasee wrote: When following a HOT-update chain from the index fetch, if we notice that the root tuple is dead and it is HOT-updated, we try to prune the chain to the smallest possible length. To do that, the share lock is upgraded to an exclusive lock and the tuple chain is followed till we find a live/recently-dead tuple. At that point, the root t_ctid is made point to that tuple. In order I assume you meant recently-dead here, rather than live/recently-dead, because we aren't going to change live ctids, right? Recently dead means still live to somebody, so those tids better not change either. But I don't think that's what he meant. I'm more worried about the deadlock possibilities inherent in trying to upgrade a buffer lock. We do not have deadlock detection for LWLocks. I am guessing he is going to have to release the lock, then ask for an exclusive one. -- Bruce Momjian [EMAIL PROTECTED] http://momjian.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. + ---(end of broadcast)--- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
Re: [PATCHES] [HACKERS] HOT WIP Patch - version 2
On 2/20/07, Bruce Momjian [EMAIL PROTECTED] wrote: Tom Lane wrote: Recently dead means still live to somebody, so those tids better not change either. But I don't think that's what he meant. I'm more worried about the deadlock possibilities inherent in trying to upgrade a buffer lock. We do not have deadlock detection for LWLocks. I am guessing he is going to have to release the lock, then ask for an exclusive one. Yes, thats what is done. Since we try to prune the HOT-update chain even in the SELECT path, we upgrade the lock only if we are sure that there is atleast one tuple that can be removed from the chain or the root needs to be fixed (broken ctid chain for some reason). Thanks, Pavan -- EnterpriseDB http://www.enterprisedb.com
