Re: Fwd: [HACKERS] How does the partitioned lock manager works?
Ah... It seems that a item is calculated its hash value, get the bucket number from it and insert into that bucket chain. The insertion has nothing to do with partition number(but Alvaro says which hash is used depends on the partition number. I haven't really understood this: how can we get a hash value without deciding which hash to use? ). However, when we travel along a chain to get a item, we can infer its partition number from its hash value. My problem is, I'm not so sure about the process stated above, because in that way, items in ONE chain may belong to different partitions,and it is obviously conflicted with so that different partitions use different hash chains as README mentioned. 2007/4/28, Tom Lane [EMAIL PROTECTED]: It's not that hard: the bucket number is some number of low-order bits of the hash value, and the partition number is some smaller (or at most equal) number of low-order bits of the hash value. regards, tom lane
Re: Fwd: [HACKERS] How does the partitioned lock manager works?
2007/4/28, Heikki Linnakangas [EMAIL PROTECTED]: 3. Lock that partition 6. Unlock partition I suddenly realize that LW locks are used to manage the lock hash table.So when a item is to be inserted into hash table, we must gain that partition lock first to change that table. As the insertion algorithm described, a specific partition lock manage some items, but these items can be stored in anywhere of the hash table,not necessarily in a bucket chain. So there are some problems with different partitions use different hash chains, a partition can use different hash chains,too. Am I right?
Re: Fwd: [HACKERS] How does the partitioned lock manager works?
Cui Shijun wrote: As the insertion algorithm described, a specific partition lock manage some items, but these items can be stored in anywhere of the hash table,not necessarily in a bucket chain. So there are some problems with different partitions use different hash chains, a partition can use different hash chains,too. Am I right? No, you're still confused. Each bucket in the hash table is a chain. Each chain can have 0, 1, or more items. I'd suggest that you study how the normal non-partitioned hash tables work first. The partitioning is a straightforward extension of that. -- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com ---(end of broadcast)--- TIP 6: explain analyze is your friend
Fwd: [HACKERS] How does the partitioned lock manager works?
-- Forwarded message -- From: rancpine cui [EMAIL PROTECTED] Date: 2007-4-27 下午9:22 Subject: Re: [HACKERS] How does the partitioned lock manager works? To: Heikki Linnakangas [EMAIL PROTECTED] Thanks for your reply. :-) I've seen from the README that The shared-memory hash tables for LOCKs and PROCLOCKs are organized so that different partitions use different hash chains, and thus there is no conflict in working with objects in different partitions. What does hash chains mean? As the dynahash.c's partitioned table mechanism suggests, a lock's bucket number can be calculated from its hash value, then it will be inserted into that bucket,so how does partition number works? Is it only a flag which suggests the partition the lock belongs to when we want to use that lock? I can't find a way to manage locks via partition...
Re: Fwd: [HACKERS] How does the partitioned lock manager works?
rancpine cui escribió: I've seen from the README that The shared-memory hash tables for LOCKs and PROCLOCKs are organized so that different partitions use different hash chains, and thus there is no conflict in working with objects in different partitions. What does hash chains mean? Each hash chain is a different, separate, independent hash struct. As the dynahash.c's partitioned table mechanism suggests, a lock's bucket number can be calculated from its hash value, then it will be inserted into that bucket,so how does partition number works? Which hash is used depends on the partition number. -- Alvaro Herrerahttp://www.CommandPrompt.com/ PostgreSQL Replication, Consulting, Custom Development, 24x7 support ---(end of broadcast)--- TIP 4: Have you searched our list archives? http://archives.postgresql.org
Re: Fwd: [HACKERS] How does the partitioned lock manager works?
Alvaro Herrera [EMAIL PROTECTED] writes: rancpine cui escribió: What does hash chains mean? Each hash chain is a different, separate, independent hash struct. It's pretty much equivalent to hash bucket --- this comment says chain because it's focusing on the physical representation of the bucket as a linked list, whereas bucket doesn't presume anything about how the elements in the bucket are stored. regards, tom lane ---(end of broadcast)--- TIP 5: don't forget to increase your free space map settings
Re: Fwd: [HACKERS] How does the partitioned lock manager works?
2007/4/27, Alvaro Herrera [EMAIL PROTECTED]: Which hash is used depends on the partition number. So the method of calculating the bucket number can promise that all items in the bucket link list belong to ONE partition?
Re: Fwd: [HACKERS] How does the partitioned lock manager works?
rancpine cui [EMAIL PROTECTED] writes: So the method of calculating the bucket number can promise that all items in the bucket link list belong to ONE partition? It's not that hard: the bucket number is some number of low-order bits of the hash value, and the partition number is some smaller (or at most equal) number of low-order bits of the hash value. regards, tom lane ---(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
