Re: [PERFORM] fsync and battery-backed caches

2006-02-28 Thread Javier Somoza
Yeah, i saw it. It says full-page-writes can be disabled without problems. But i wanted to confirm fsync cannot be disabled although i have battery. Thanks!! :-) We do mention battery-backed cache in our docs: http://www.postgresql.org/docs/8.1/static/wal.html If it is unclear,

[PERFORM] Different disks for xlogs and data

2006-02-28 Thread Javier Somoza
Hi, is interesting to do it when using RAID 1+0? Thx

[PERFORM] vacuum, analyze and reindex

2006-02-28 Thread Javier Somoza
Hi all I've a question about vacuuming, ... Vacuum: cleans out obsolete and deleted registers... Analyze: update statistics for the planner Reindex: rebuild indexes I think the correct order to perform the database maintenance for performance is: 1 - Vacuum 2 - Reindex 3 -

Re: [PERFORM] vacuum, analyze and reindex

2006-02-28 Thread Christopher Browne
Centuries ago, Nostradamus foresaw when [EMAIL PROTECTED] (Javier Somoza) would write:     Hi all     I've a question about vacuuming, ...     Vacuum: cleans out obsolete and deleted registers...     Analyze:  update statistics for the planner    

Re: [PERFORM] Different disks for xlogs and data

2006-02-28 Thread Ron
At 04:45 AM 2/28/2006, Javier Somoza wrote: Hi, is interesting to do it (use different HD sets AKA LUNs for xlogs than for data) when using RAID 1+0? If interesting means this increases performance, this is not a simple question. Regardless of what RAID level you use, under the proper

[PERFORM] temporary indexes

2006-02-28 Thread Kevin Grittner
Just a wouldn't it be nice if sort of feature request. I'm not sure how practical it is. Someone in our organization wrote a data fix query, which has sort of odd logic, but it does what they need. The problem is that it ran for 14 hours in a test against a copy of the data. I looked at it and

Re: [PERFORM] [HACKERS] temporary indexes

2006-02-28 Thread Jim C. Nasby
On Tue, Feb 28, 2006 at 09:44:08AM -0600, Kevin Grittner wrote: It struck me that it would be outstanding if the planner could recognize this sort of situation, and build a temporary index based on the snapshot of the data visible to the transaction. It seems to me that the obvious downside

Re: [PERFORM] temporary indexes

2006-02-28 Thread Tom Lane
Kevin Grittner [EMAIL PROTECTED] writes: It struck me that it would be outstanding if the planner could recognize this sort of situation, and build a temporary index based on the snapshot of the data visible to the transaction. I don't think that's an appropriate solution at all. What it

Re: [PERFORM] [HACKERS] temporary indexes

2006-02-28 Thread Tom Lane
Jim C. Nasby [EMAIL PROTECTED] writes: FWIW, Sybase supported something similar a long time ago. It had the ability to build a temporary 'clustered table' (think index organized table) when there was enough benefit to do so. This is actually much easier to make happen inside a transaction for

Re: [PERFORM] [HACKERS] temporary indexes

2006-02-28 Thread Kevin Grittner
On Tue, Feb 28, 2006 at 11:05 am, in message [EMAIL PROTECTED], Tom Lane [EMAIL PROTECTED] wrote: The issue at hand really has nothing to do with temp indexes, it's with the constrained way that the planner deals with EXISTS subplans. Yet when the index exists, the query is optimized well.

Re: [PERFORM] fsync and battery-backed caches

2006-02-28 Thread Javier Somoza
Ups sorry. Actually, you can't assume that a BBU means you can safely disable full-page-writes. Depending on the controller, it's still possible to end up with partially written pages. BTW, if your mailer makes doing so convenient, it would be nice to trim down your .signature; note that

Re: [PERFORM] [HACKERS] temporary indexes

2006-02-28 Thread Tom Lane
Kevin Grittner [EMAIL PROTECTED] writes: EXISTS works in situations where you need to compare on multiple columns, so it is useful in many situations where IN or MIN/MAX techniques just don't work. IN works fine on multiple columns: (foo, bar, baz) IN (SELECT x, y, z FROM ...)

Re: [PERFORM] [HACKERS] temporary indexes

2006-02-28 Thread Steinar H. Gunderson
On Tue, Feb 28, 2006 at 11:55:32AM -0600, Kevin Grittner wrote: Also, EXISTS works in situations where you need to compare on multiple columns, so it is useful in many situations where EXISTS or MIN/MAX techniques just don't work. Sorry. That should have read: EXISTS works in situations

Re: [PERFORM] fsync and battery-backed caches

2006-02-28 Thread Jim C. Nasby
Ok, you absolutely can't guarantee you won't get partial page writes then. A UPS buys you no more data safety than being plugged directly into the wall. UPS's fail. People trip over cords. Breakers fail. Even if you have multiple power supplies on multiple circuits fed by different UPS's you can

Re: [PERFORM] [HACKERS] temporary indexes

2006-02-28 Thread Jim C. Nasby
On Tue, Feb 28, 2006 at 11:36:28AM -0600, Kevin Grittner wrote: digression I'm all for that. So far, we've been going after the low-hanging fruit in our use of PostgreSQL. When we get to the main applications, we're going to be dealing with a lot more in the way of EXISTS clauses. The

Re: [PERFORM] [HACKERS] temporary indexes

2006-02-28 Thread Kevin Grittner
On Tue, Feb 28, 2006 at 11:05 am, in message [EMAIL PROTECTED], Tom Lane [EMAIL PROTECTED] wrote: The limiting factor is that EXISTS subplans aren't flattened ... and once that's fixed, I doubt the example would need any new kind of join support. I rewrote the query to use IN predicates

Re: [PERFORM] wal sync method

2006-02-28 Thread Tom Lane
PFC [EMAIL PROTECTED] writes: Just a stupid question about the various fsync settings. There is fsync=off, but is there fsync=fflush ? fflush would mean only an OS crash could cause data loss, I think.it could be useful for some applications where you need a speed

[PERFORM] nested query on last n rows of huge table

2006-02-28 Thread jcfischer
Hi list I'm fairly new to Postgres so bear with me. Googling and searching the list, I didn't find anything that resembled my problem. I have a large table with ca. 10 million inserts per day (fairly simple data: timestam, a couple of id's and a varchar message) I run a query every couple of

Re: [PERFORM] nested query on last n rows of huge table

2006-02-28 Thread jcfischer
sorry: Postgres 8.0.2 server. The EXPLAIN ANALYZE for the query looks like this: explain analyze select syslog.logs.eventtime,assets.hosts.name,syslog.processes.name as process from syslog.logs,assets.hosts,assets.ipaddrs,assets.macaddrs,syslog.processes where msg like '%session opened for user

[PERFORM] Large Table With Only a Few Rows

2006-02-28 Thread Nik
I have a table that has only a few records in it at the time, and they get deleted every few seconds and new records are inserted. Table never has more than 5-10 records in it. However, I noticed a deteriorating performance in deletes and inserts on it. So I performed vacuum analyze on it three

Re: [PERFORM] triggers, performance Was: Re: [GENERAL] rotate records

2006-02-28 Thread Jeevanandam, Kathirvel (IE10)
I am using triggers for all the events (insert,delete,update) please find the details below. trg_delpointtable BEFORE DELETE ON pointtable FOR EACH ROW EXECUTE PROCEDURE pp_delpointtable() trg_insdelpoints AFTER DELETE ON pointtable FOR EACH ROW EXECUTE PROCEDURE pp_insdelpoints()

Re: [PERFORM] Large Table With Only a Few Rows

2006-02-28 Thread Bruno Wolff III
On Mon, Feb 27, 2006 at 06:48:02 -0800, Nik [EMAIL PROTECTED] wrote: I have a table that has only a few records in it at the time, and they get deleted every few seconds and new records are inserted. Table never has more than 5-10 records in it. However, I noticed a deteriorating

Re: [PERFORM] nested query on last n rows of huge table

2006-02-28 Thread Michael Glaesemann
On Feb 24, 2006, at 23:13 , jcfischer wrote: Is there a way to limit the expensive query to only those last 1000 (or whatever) results? I have tried to nest SELECTS but my SQL-fu is to limited to get anything through the SQL processor :-) The basics of a subquery are: SELECT expensive