Tom Lane wrote:
> Gaetano Mendola <[EMAIL PROTECTED]> writes:
> > BTW, why not do an automatic vacuum instead of shutdown ? At least the
> > DB do not stop working untill someone study what the problem is and
> > how solve it.
>
> No, the entire point of this discussion is to whup the DBA upside t
Evgeny Rodichev <[EMAIL PROTECTED]> writes:
> No, it does. Let's try the simplest test:
>
> for (i = 0; i < LEN; i++) {
> write (fd, buf, 512);
> if (sync) fsync (fd);
> }
>
> with sync = 0 and 1, and you'll see the difference.
Uh, I'm sure you'll see a difference, one will be limited
""Magnus Hagander"" <[EMAIL PROTECTED]>
news:[EMAIL PROTECTED]
>
> This is what we have discovered. AFAIK, all other major databases or
> other similar apps (like exchange or AD) all open files with
> FILE_FLAG_WRITE_THROUGH and do *not* use fsync. It might give noticably
> better performance with
Greg Stark wrote:
> Gaetano Mendola <[EMAIL PROTECTED]> writes:
>
>
>>We do ~4000 txn/minute so in 6 month you are screewd up...
>
>
> Sure, but if you ran without vacuuming for 6 months, wouldn't you notice the
> huge slowdowns from all those dead tuples before that?
>
In my applications yes
On Fri, 17 Feb 2005, Greg Stark wrote:
Oliver Jowett <[EMAIL PROTECTED]> writes:
So Linux is indeed doing a cache flush on fsync
Actually I think the root of the problem was precisely that Linux does not
issue any sort of cache flush commands to drives on fsync.
No, it does. Let's try the simplest
On Fri, 18 Feb 2005, Oliver Jowett wrote:
Evgeny Rodichev wrote:
Write cache is enabled under Linux by default all the time I make deal
with it (since 1993).
It doesn't interfere with fsync(), as linux kernel uses cache flush for
fsync.
The problem is that most IDE drives lie (or perhaps you could
On Thu, 17 Feb 2005, Tom Lane wrote:
Evgeny Rodichev <[EMAIL PROTECTED]> writes:
Any claimed TPS rate exceeding your disk drive's rotation rate is a
red flag.
Write cache is enabled under Linux by default all the time I make deal
with it (since 1993).
You're playing with fire.
Yes. I'm lucky in th
Greg Stark wrote:
Oliver Jowett <[EMAIL PROTECTED]> writes:
So Linux is indeed doing a cache flush on fsync
Actually I think the root of the problem was precisely that Linux does not
issue any sort of cache flush commands to drives on fsync. There was some talk
on linux-kernel of what how they co
Oliver Jowett <[EMAIL PROTECTED]> writes:
> So Linux is indeed doing a cache flush on fsync
Actually I think the root of the problem was precisely that Linux does not
issue any sort of cache flush commands to drives on fsync. There was some talk
on linux-kernel of what how they could take advant
On Wed, 16 Feb 2005, Tom Lane wrote:
> Richard Huxton writes:
> > I seem to remember some subtle problems with dropped columns and plpgsql
> > functions - could be one of those still left.
>
> It looks like the code that handles returning a RECORD variable doesn't
> cope with dropped columns in
> "Magnus Hagander" <[EMAIL PROTECTED]> writes:
> > Is there actually a reason why we don't use O_DIRECT on Unix?
>
> Portability, or rather the complete lack of it. Stuff that isn't in
the
> Single Unix Spec is a hard sell.
Well, how about this (ok, maybe I'm way out in left field):
Change fsyn
Evgeny Rodichev wrote:
Write cache is enabled under Linux by default all the time I make deal
with it (since 1993).
It doesn't interfere with fsync(), as linux kernel uses cache flush for
fsync.
The problem is that most IDE drives lie (or perhaps you could say the
specification is ambiguous) about
"Magnus Hagander" <[EMAIL PROTECTED]> writes:
> Is there actually a reason why we don't use O_DIRECT on Unix?
Portability, or rather the complete lack of it. Stuff that isn't in the
Single Unix Spec is a hard sell.
regards, tom lane
---(end of bro
>After multiple runs on different blocksizes( a few anomalous results
>aside), I didn't see a whole lot of difference between
>FILE_FLAG_NO_BUFFERING being on or off for writing performance.
>However, with NO_BUFFERING set, the file is not *read* cached at all.
>While the performance is on not terr
Evgeny Rodichev <[EMAIL PROTECTED]> writes:
>> Any claimed TPS rate exceeding your disk drive's rotation rate is a
>> red flag.
> Write cache is enabled under Linux by default all the time I make deal
> with it (since 1993).
You're playing with fire.
> fsync() really works fine as I switch off m
> "Magnus Hagander" <[EMAIL PROTECTED]> writes:
> > Tom, if you look at all the requirements of FILE_FLAG_NO_BUFFERING
on
> >
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/fileio/
> > base/createfile.asp, can you say offhand if the WAL code fulfills
them?
>
> If I'm reading it r
On Thu, 17 Feb 2005, Tom Lane wrote:
Christopher Kings-Lynne <[EMAIL PROTECTED]> writes:
WinXP fsync = true 20-28 tps
WinXP fsync = false 600 tps
Linux fsync = true 800 tps
Linux fsync = false 980 tps
Wow, that's terrible on Windows. If there's a solution, it'd be nice to
"Magnus Hagander" <[EMAIL PROTECTED]> writes:
> Tom, if you look at all the requirements of FILE_FLAG_NO_BUFFERING on
> http://msdn.microsoft.com/library/default.asp?url=/library/en-us/fileio/
> base/createfile.asp, can you say offhand if the WAL code fulfills them?
If I'm reading it right, you ar
> One point that I no longer recall the reasoning behind is that xlog.c
> doesn't think O_SYNC is a preferable default over fsync. We'd
certainly
> want to hack xlog.c to change its mind about that, at least on
Windows;
> assuming that the FILE_FLAG way is indeed faster.
I also confirmed that the
>> > WinXP fsync = true 20-28 tps
>> > WinXP fsync = false 600 tps
>> > Linux fsync = true 800 tps
>> > Linux fsync = false 980 tps
>>
>> Wow, that's terrible on Windows. If there's a solution, it'd be nice
>to
>> backport it...
>>
>
>there is. I just rigged up a test be
Evgeny Rodichev wrote:
There are two different concerns here.
1. transactions loss because of unexpected power loss and/or system failure
2. inconsistent database state
For many application (1) is fairly acceptable, and (2) is not.
So I'd like to formulate my questions by another way.
- if PostgeSQ
Christopher Kings-Lynne <[EMAIL PROTECTED]> writes:
>> WinXP fsync = true 20-28 tps
>> WinXP fsync = false 600 tps
>> Linux fsync = true 800 tps
>> Linux fsync = false 980 tps
> Wow, that's terrible on Windows. If there's a solution, it'd be nice to
> backport it...
Actu
> > WinXP fsync = true 20-28 tps
> > WinXP fsync = false 600 tps
> > Linux fsync = true 800 tps
> > Linux fsync = false 980 tps
>
> Wow, that's terrible on Windows. If there's a solution, it'd be nice
to
> backport it...
>
there is. I just rigged up a test benchmark com
There are two different concerns here.
1. transactions loss because of unexpected power loss and/or system failure
2. inconsistent database state
For many application (1) is fairly acceptable, and (2) is not.
So I'd like to formulate my questions by another way.
- if PostgeSQL is running without fs
Some addition:
WinXP fsync = true 20-28 tps
WinXP fsync = false 600 tps
Linux fsync = true 800 tps
Linux fsync = false 980 tps
Wow, that's terrible on Windows. If there's a solution, it'd be nice to
backport it...
Chris
---(end of broadcast)---
"Magnus Hagander" <[EMAIL PROTECTED]> writes:
> Oh, and finally. The win32 commands have the following options:
> FILE_FLAG_NO_BUFFERING. This disables the cache completely. It also has
> lots of limits, like every read and write has to be on a sector boundary
> etc. It gives great performance with
> >Doesn't Windows support O_SYNC (or even better O_DSYNC) flag to
open()?
> >That should be the Posixy spelling of FILE_FLAG_WRITE_THROUGH, if the
> >latter means what I suppose it does.
>
> They should, but someone said it didn't work. I haven't followed up on
> it, though, so it is quite possib
>>Doesn't Windows support O_SYNC (or even better O_DSYNC) flag
>to open()?
>>That should be the Posixy spelling of FILE_FLAG_WRITE_THROUGH, if the
>>latter means what I suppose it does.
>
>They should, but someone said it didn't work. I haven't
>followed up on it, though, so it is quite possible
On Thu, 17 Feb 2005, Andrew Dunstan wrote:
(the results are interesting, though - with fsync off Windows and Linux are
in the same performance ballpark.)
Some addition:
WinXP fsync = true 20-28 tps
WinXP fsync = false 600 tps
Linux fsync = true 800 tps
Linux fsync = false 9
>> Things worth experimenting with (these are all untested, so please
>> report any successes):
>> 1) Try reformatting with a cluster size of 8Kb (the pg page size), if
>> you can.
>> 2) Disable the last access time (like noatime on linux). "fsutil
>> behavior set disablelastaccess 1"
>> 3) Disable
"Magnus Hagander" <[EMAIL PROTECTED]> writes:
> This is what we have discovered. AFAIK, all other major databases or
> other similar apps (like exchange or AD) all open files with
> FILE_FLAG_WRITE_THROUGH and do *not* use fsync. It might give noticably
> better performance with an O_DIRECT style W
>> This is what we have discovered. AFAIK, all other major databases or
>> other similar apps (like exchange or AD) all open files with
>> FILE_FLAG_WRITE_THROUGH and do *not* use fsync. It might
>give noticably
>> better performance with an O_DIRECT style WAL logging at
>least. But I'm
>> unsure
>>So by all means turn off fsync if you want the performance gain *and*
>>you accept the risk. But if you do, don't come crying later that your
>>data has been lost or corrupted.
>
>>(the results are interesting, though - with fsync off Windows
>and Linux
>>are in the same performance ballpark.
Tom Lane wrote:
Thomas Hallgren <[EMAIL PROTECTED]> writes:
My question is, what happens when the evaluator doesn't need more rows?
Will it:
a) call the function with call_cntr >= max_calls?
b) continue calling until the set is exhausted anyway?
c) simply stop calling?
(c)
a) seems unli
Thomas Hallgren <[EMAIL PROTECTED]> writes:
> My question is, what happens when the evaluator doesn't need more rows?
> Will it:
> a) call the function with call_cntr >= max_calls?
> b) continue calling until the set is exhausted anyway?
> c) simply stop calling?
(c)
> a) seems unlikely since ma
In <[EMAIL PROTECTED]>, on 02/17/05
at 10:21 AM, Andrew Dunstan <[EMAIL PROTECTED]> said:
>E.Rodichev wrote:
>>
>> This problem is addressed by file system (fsck, journalling etc.).
>> Is it reasonable to handle it directly within application?
>>
>>
>In the words of the Duke of Wellington,
E.Rodichev wrote:
This problem is addressed by file system (fsck, journalling etc.).
Is it reasonable to handle it directly within application?
In the words of the Duke of Wellington, "If you believe that you'll
believe anything."
Please review past discussions on the mailing lists on this poin
"E.Rodichev" <[EMAIL PROTECTED]> writes:
> On Thu, 17 Feb 2005, Christopher Kings-Lynne wrote:
>
>> Fsync is so that when your computer loses power without warning, you
>> will have no data loss.
>>
>> If you turn it off, you run the risk of losing data if you lose power.
>>
>> Chris
>
> This prob
On Thu, 17 Feb 2005 17:54:38 +0300 (MSK)
"E.Rodichev" <[EMAIL PROTECTED]> wrote:
> On Thu, 17 Feb 2005, Christopher Kings-Lynne wrote:
>
> >> The general question is - does PostgreSQL really need fsync? I
> >suppose it> is a question for design, not platform-specific one. It
> >sounds like only> o
On Thu, 17 Feb 2005, Christopher Kings-Lynne wrote:
The general question is - does PostgreSQL really need fsync? I suppose it
is a question for design, not platform-specific one. It sounds like only
one scenario, when fsync is useful, is to interprocess communication via
open file. But PostgreSQL u
On Thu, 17 Feb 2005, Magnus Hagander wrote:
Hi,
looking for the way how to increase performance at Windows XP
box, I found the parameters
#fsync = true # turns forced
synchronization on or off
#wal_sync_method = fsync# the default varies across platforms:
The general question is - does PostgreSQL really need fsync? I suppose it
is a question for design, not platform-specific one. It sounds like only
one scenario, when fsync is useful, is to interprocess communication via
open file. But PostgreSQL utilize IPC for this, so does fsync is really
require
> Things worth experimenting with (these are all untested, so please
> report any successes):
> 1) Try reformatting with a cluster size of 8Kb (the pg page size), if
> you can.
What about recompiling pg with a 4k block size. Win32 file cluster
sizes and memory allocation units are both on 4k boun
> Gaetano Mendola <[EMAIL PROTECTED]> writes:
>
>> We do ~4000 txn/minute so in 6 month you are screewd up...
>
> Sure, but if you ran without vacuuming for 6 months, wouldn't you notice
> the
> huge slowdowns from all those dead tuples before that?
>
>
I would think that only applies to databases
> Would there be any value in incrementing by 2 for index accesses and 1
> for seq-scans/vacuums? Actually, it should probably be a ratio based on
> random_page_cost shouldn't it?
What happens with very small hot tables that are only a few pages and thus have
no index defined.
I think it woul
John,
You are supposed to free resources used to produce the rows before srf_return_next();
I can (and must) free up the resources used to produce one single row at
that time yes, but I might have resources that is common to all rows.
Let's assume that I have a file open for instance. I read one
> Hi,
>
> looking for the way how to increase performance at Windows XP
> box, I found the parameters
>
> #fsync = true # turns forced
> synchronization on or off
> #wal_sync_method = fsync# the default varies across platforms:
> # fsyn
> ... c) would be very bad since it
> doesn't give me any chance to release the resources that
> where used in order to produce the rows.
You are supposed to free resources used to produce the rows before
srf_return_next();
The actual rows are pfree()'d by pg. (an dso are any other palloc()'d
It looks like the code that handles returning a RECORD variable doesn't
cope with dropped columns in the function result rowtype.
(If you instead declare rec as usno%rowtype, you get a different set
of misbehaviors after adding/dropping columns, so that code path isn't
perfect either :-()
Isn't it
Some SQL constructs will be satisfied before all rows of a set has been
examined. I'm thinking of for instance:
EXISTS(SELECT * FROM y WHERE y.a > 0)
If the first row of collection y fulfills the WHERE predicate, there's
no reason to continue perusing the rest of the rows. Now, what if 'y' is
a
And most databases get a mix of updates and selects. I would expect it would
be pretty hard to go that long with any significant level of update activity
and no vacuums and not notice the performance problems from the dead tuples.
I think the people who've managed to shoot themselves in the foot t
When I try to input a unicode caracter which code is greater than
U+2, phpPgAdmin returns the following error message :
ERROR: Unicode characters greater than or equal to 0x1 are not
supported
Could someone fix this problem ?
If yes, would you please tell me where can i download the ne
Tom Lane wrote:
"Jim C. Nasby" <[EMAIL PROTECTED]> writes:
The advantage of using a counter instead of a simple active
bit is that buffers that are (or have been) used heavily will be able to
go through several sweeps of the clock before being freed. Infrequently
used buffers (such as those from a
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