Re: Reducing relation locking overhead
От | Hannu Krosing |
---|---|
Тема | Re: Reducing relation locking overhead |
Дата | |
Msg-id | 1134035930.3641.29.camel@localhost.localdomain обсуждение исходный текст |
Ответ на | Re: Reducing relation locking overhead ("Jim C. Nasby" <jim@nasby.net>) |
Ответы |
Improving free space usage (was: Reducing relation locking overhead)
|
Список | pgsql-hackers |
Ühel kenal päeval, N, 2005-12-08 kell 01:08, kirjutas Jim C. Nasby: > On Thu, Dec 08, 2005 at 08:57:42AM +0200, Hannu Krosing wrote: > > ??hel kenal p??eval, N, 2005-12-08 kell 00:16, kirjutas Jim C. Nasby: > > > On Sat, Dec 03, 2005 at 10:15:25AM -0500, Greg Stark wrote: > > > > Tom Lane <tgl@sss.pgh.pa.us> writes: > > > > > What's worse, once you have excluded writes you have to rescan the entire > > > > > table to be sure you haven't missed anything. So in the scenarios where this > > > > > whole thing is actually interesting, ie enormous tables, you're still > > > > > talking about a fairly long interval with writes locked out. Maybe not as > > > > > long as a complete REINDEX, but long. > > > > > > > > I was thinking you would set a flag to disable use of the FSM for > > > > inserts/updates while the reindex was running. So you would know where to find > > > > the new tuples, at the end of the table after the last tuple you read. > > > > > > What about keeping a seperate list of new tuples? Obviously we'd only do > > > this when an index was being built on a table. > > > > The problem with separate list is that it can be huge. For example on a > > table with 200 inserts/updates per second an index build lasting 6 hours > > would accumulate total on 6*3600*200 = 4320000 new tuples. > > Sure, but it's unlikely that such a table would be very wide, so 4.3M > tuples would probably only amount to a few hundred MB of data. It's also > possible that this list could be vacuumed by whatever the regular vacuum > process is for the table. I think that keeping such list as part the table at well defined location (like pages from N to M) is the best strategy, as it will automatically make all new tuples available to parallel processes and avoids both duplicate storage as well as the the need for changing insert/update code. --------------- Hannu
В списке pgsql-hackers по дате отправления: