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Commit 27330595 authored by Bruce Momjian's avatar Bruce Momjian
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Place statement_timeout in proper order in docs, from Bruno Wolff III.

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I wrote:
> scott.marlowe wrote:
......@@ -7447,7 +7447,7 @@ References: <Pine.LNX.4.33.0209120945260.10924-100000@css120.ihs.com>
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scott.marlowe wrote:
> On Fri, 13 Sep 2002, Justin Clift wrote:
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Curt Sampson <cjs@cynic.net> writes:
> On Thu, 12 Sep 2002, Justin Clift wrote:
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On Wed, Sep 18, 2002 at 08:01:42PM -0400, Bruce Momjian wrote:
......@@ -7626,91 +7626,6 @@ Ross
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From mascarm@mascari.com Thu Sep 19 01:24:42 2002
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Date: Thu, 19 Sep 2002 01:23:45 -0400
From: Mike Mascari <mascarm@mascari.com>
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To: Bruce Momjian <pgman@candle.pha.pa.us>
cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] Win32 rename()/unlink() questions
References: <200209190001.g8J01gG13849@candle.pha.pa.us>
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Bruce Momjian wrote:
> I am working with several groups getting the Win32 port ready for 7.4
> and I have a few questions:
>
> What is the standard workaround for the fact that rename() isn't atomic
> on Win32? Do we need to create our own locking around the
> reading/writing of files that are normally updated in place using
> rename()?
Visual C++ comes with the source to Microsoft's C library:
rename() calls MoveFile() which will error if:
1. The target file exists
2. The source file is in use
MoveFileEx() (not available on 95/98) can overwrite the target
file if it exists. The Apache APR portability library uses
MoveFileEx() to rename files if under NT/XP/2K vs. a sequence of :
1. CreateFile() to test for target file existence
2. DeleteFile() to remove the target file
3. MoveFile() to rename the old file to new
under Windows 95/98. Of course, some other process could create
the target file between 2 and 3, so their rename() would just
error out in that situation. I haven't tested it, but I recall
reading somewhere that MoveFileEx() has the ability to rename an
opened file. I'm 99% sure MoveFile() will fail if the source
file is open.
>
> Second, when you unlink() a file on Win32, do applications continue
> accessing the old file contents if they had the file open before the
> unlink?
>
unlink() just calls DeleteFile() which will error if:
1. The target file is in use
CreateFile() has the option:
FILE_FLAG_DELETE_ON_CLOSE
which might be able to be used to simulate traditional unlink()
behavior.
Hope that helps,
Mike Mascari
mascarm@mascari.com
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Bruce Momjian wrote:
> I am working with several groups getting the Win32 port ready for 7.4
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> On Wed, Sep 18, 2002 at 08:01:42PM -0400, Bruce Momjian wrote:
>
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Christopher Kings-Lynne wrote:
>>On Wed, Sep 18, 2002 at 08:01:42PM -0400, Bruce Momjian wrote:
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Mike Mascari wrote:
> Bruce Momjian wrote:
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Bruce Momjian wrote:
> > > Second, when you unlink() a file on Win32, do applications continue
> > > accessing the old file contents if they had the file open before the
> > > unlink?
> > >
> >
> > unlink() just calls DeleteFile() which will error if:
> >
> > 1. The target file is in use
> >
> > CreateFile() has the option:
> >
> > FILE_FLAG_DELETE_ON_CLOSE
> >
> > which might be able to be used to simulate traditional unlink()
> > behavior.
>
> No, that flag isn't going to help us. I wonder what MoveFileEx does if
> the target file exists _and_ is open by another user? I don't see any
> loop in that Win32 rename() routine, and I looked at the Unix version of
> apr_file_rename and its just a straight rename() call.
This says that if the target is in use, it is overwritten:
http://support.microsoft.com/default.aspx?scid=KB;EN-US;q140570&
While I think that is good news, does it open the problem of other
readers reading partial updates to the file and therefore seeing
garbage. Not sure how to handle that, nor am I even sure how I would
test it.
--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073
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From: Bruce Momjian <pgman@candle.pha.pa.us>
Message-ID: <200209200250.g8K2ofr29042@candle.pha.pa.us>
Subject: Re: [HACKERS] Win32 rename()/unlink() questions
In-Reply-To: <200209192024.g8JKO1g10337@candle.pha.pa.us>
To: Bruce Momjian <pgman@candle.pha.pa.us>
Date: Thu, 19 Sep 2002 22:50:41 -0400 (EDT)
cc: Mike Mascari <mascarm@mascari.com>,
PostgreSQL-development <pgsql-hackers@postgresql.org>
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Bruce Momjian wrote:
> > > Second, when you unlink() a file on Win32, do applications continue
......@@ -8208,9 +8048,6 @@ test it.
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073
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From mascarm@mascari.com Fri Sep 20 00:02:33 2002
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Bruce Momjian wrote:
> Bruce Momjian wrote:
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Mike Mascari wrote:
> I read the article and did not come away with that conclusion.
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> Mike Mascari wrote:
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From mascarm@mascari.com Fri Sep 20 01:01:37 2002
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To: Mike Mascari <mascarm@mascari.com>
cc: Bruce Momjian <pgman@candle.pha.pa.us>,
PostgreSQL-development
<pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] Win32 rename()/unlink() questions
References: <200209200405.g8K45RV12655@candle.pha.pa.us> <3D8AA4B2.8090507@mascari.com>
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Mike Mascari wrote:
> Bruce Momjian wrote:
>
>> Mike Mascari wrote:
>>
>>> I will do some testing with concurrency and let you know. But don't
>>> get your hopes up. This is one of the many advantages that
>>> TABLESPACEs have when more than one relation is stored in a single
>>> DATAFILE. There was Oracle for MS-DOS, after all..
>>
>>
>>
>> I was focusing on handling of pg_pwd and other config file that are
>> written by various backend while other backends are reading them. The
>> actual data files should be OK because we have an exclusive lock when we
>> are adding/removing them.
>>
>
> OK. So you want to test:
>
> 1. Process 1 opens "foo"
> 2. Process 2 opens "foo"
> 3. Process 1 renames "foo" to "bar"
> 4. Process 2 can safely read from its open file handle
Actually, looking at the pg_pwd code, you want to determine a
way for:
1. Process 1 opens "foo"
2. Process 2 opens "foo"
3. Process 1 creates "bar"
4. Process 1 renames "bar" to "foo"
5. Process 2 can continue to read data from the open file handle
and get the original "foo" data.
Is that correct?
Mike Mascari
mascarm@mascari.com
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Mike Mascari wrote:
> Bruce Momjian wrote:
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Mike Mascari wrote:
> Actually, looking at the pg_pwd code, you want to determine a
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> Mike Mascari wrote:
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On Fri, 20 Sep 2002, Mike Mascari wrote:
> Bruce Momjian wrote:
> > Mike Mascari wrote:
> >
> >>Actually, looking at the pg_pwd code, you want to determine a
> >>way for:
> >>
> >>1. Process 1 opens "foo"
> >>2. Process 2 opens "foo"
> >>3. Process 1 creates "bar"
> >>4. Process 1 renames "bar" to "foo"
> >>5. Process 2 can continue to read data from the open file handle
> >>and get the original "foo" data.
> >
> >
> > Yep, that's it.
> >
>
> So far, MoveFileEx("foo", "bar", MOVEFILE_REPLACE_EXISTING)
> returns "Access Denied" when Process 1 attempts the rename. But
> I'm continuing to investigate the possibilities...
Does a sequence like
Process 1 opens "foo"
Process 2 opens "foo"
Process 1 creates "bar"
Process 1 renames "foo" to <something>
- where something is generated to not overlap an existing file
Process 1 renames "bar" to "foo"
Process 2 continues reading
let you do the replace and keep reading (at the penalty that
you've now got to have a way to know when to remove the
various <something>s)
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To: Mike Mascari <mascarm@mascari.com>
cc: Bruce Momjian <pgman@candle.pha.pa.us>,
PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] Win32 rename()/unlink() questions
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On Fri, 20 Sep 2002, Mike Mascari wrote:
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Date: Fri, 20 Sep 2002 02:03:43 -0400
From: Mike Mascari <mascarm@mascari.com>
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To: Stephan Szabo <sszabo@megazone23.bigpanda.com>
cc: Bruce Momjian <pgman@candle.pha.pa.us>,
PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] Win32 rename()/unlink() questions
References: <20020919224718.H36366-100000@megazone23.bigpanda.com>
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Stephan Szabo wrote:
> On Fri, 20 Sep 2002, Mike Mascari wrote:
>>Bruce Momjian wrote:
>>>Mike Mascari wrote:
>>>>Actually, looking at the pg_pwd code, you want to determine a
>>>>way for:
>>>>
>>>>1. Process 1 opens "foo"
>>>>2. Process 2 opens "foo"
>>>>3. Process 1 creates "bar"
>>>>4. Process 1 renames "bar" to "foo"
>>>>5. Process 2 can continue to read data from the open file handle
>>>>and get the original "foo" data.
>>>
>>>
>>>Yep, that's it.
>>>
>>
>>So far, MoveFileEx("foo", "bar", MOVEFILE_REPLACE_EXISTING)
>>returns "Access Denied" when Process 1 attempts the rename. But
>>I'm continuing to investigate the possibilities...
>
>
> Does a sequence like
> Process 1 opens "foo"
> Process 2 opens "foo"
> Process 1 creates "bar"
> Process 1 renames "foo" to <something>
> - where something is generated to not overlap an existing file
> Process 1 renames "bar" to "foo"
> Process 2 continues reading
> let you do the replace and keep reading (at the penalty that
> you've now got to have a way to know when to remove the
> various <something>s)
Yes! Indeed that does work.
Mike Mascari
mascarm@mascari.com
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From mascarm@mascari.com Fri Sep 20 02:04:41 2002
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Stephan Szabo wrote:
> On Fri, 20 Sep 2002, Mike Mascari wrote:
......@@ -8991,57 +8618,6 @@ Mike Mascari
mascarm@mascari.com
From sszabo@megazone23.bigpanda.com Fri Sep 20 02:14:23 2002
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Date: Thu, 19 Sep 2002 23:14:14 -0700 (PDT)
From: Stephan Szabo <sszabo@megazone23.bigpanda.com>
To: Mike Mascari <mascarm@mascari.com>
cc: Bruce Momjian <pgman@candle.pha.pa.us>,
PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] Win32 rename()/unlink() questions
In-Reply-To: <3D8ABA3F.6030002@mascari.com>
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On Fri, 20 Sep 2002, Mike Mascari wrote:
> Stephan Szabo wrote:
> > On Fri, 20 Sep 2002, Mike Mascari wrote:
> >>So far, MoveFileEx("foo", "bar", MOVEFILE_REPLACE_EXISTING)
> >>returns "Access Denied" when Process 1 attempts the rename. But
> >>I'm continuing to investigate the possibilities...
> >
> >
> > Does a sequence like
> > Process 1 opens "foo"
> > Process 2 opens "foo"
> > Process 1 creates "bar"
> > Process 1 renames "foo" to <something>
> > - where something is generated to not overlap an existing file
> > Process 1 renames "bar" to "foo"
> > Process 2 continues reading
> > let you do the replace and keep reading (at the penalty that
> > you've now got to have a way to know when to remove the
> > various <something>s)
>
> Yes! Indeed that does work.
Thinking back, I think that may still fail on Win95 (using MoveFile).
Once in the past I had to work on (un)installers for Win* and I
vaguely remember Win95 being more strict than Win98 but that may just
have been with moving the executable you're currently running.
From pgsql-hackers-owner+M29185@postgresql.org Fri Sep 20 02:14:29 2002
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On Fri, 20 Sep 2002, Mike Mascari wrote:
......@@ -9109,98 +8685,6 @@ vaguely remember Win95 being more strict than Win98 but that may just
have been with moving the executable you're currently running.
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From pgsql-hackers-owner+M29189@postgresql.org Fri Sep 20 03:22:41 2002
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Date: Fri, 20 Sep 2002 03:13:26 -0400
From: Mike Mascari <mascarm@mascari.com>
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To: Stephan Szabo <sszabo@megazone23.bigpanda.com>
cc: Bruce Momjian <pgman@candle.pha.pa.us>,
PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] Win32 rename()/unlink() questions
References: <20020919230827.A36505-100000@megazone23.bigpanda.com>
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Stephan Szabo wrote:
> On Fri, 20 Sep 2002, Mike Mascari wrote:
>>
>>Yes! Indeed that does work.
>
>
> Thinking back, I think that may still fail on Win95 (using MoveFile).
> Once in the past I had to work on (un)installers for Win* and I
> vaguely remember Win95 being more strict than Win98 but that may just
> have been with moving the executable you're currently running.
Well, here's the test:
foo.txt contains "This is FOO!"
bar.txt contains "This is BAR!"
Process 1 opens foo.txt
Process 2 opens foo.txt
Process 1 sleeps 7.5 seconds
Process 2 sleeps 15 seconds
Process 1 uses MoveFile() to rename "foo.txt" to "foo2.txt"
Process 1 uses MoveFile() to rename "bar.txt" to "foo.txt"
Process 1 uses DeleteFile() to remove "foo2.txt"
Process 2 awakens and displays "This is FOO!"
On the filesystem, we then have:
foo.txt containing "This is BAR!"
The good news is that this works fine under NT 4 using just
MoveFile(). The bad news is that it requires the files be opened
using CreateFile() with the FILE_SHARE_DELETE flag set. The C
library which ships with Visual C++ 6 ultimately calls
CreateFile() via fopen() but with no opportunity through the
standard C library routines to use the FILE_SHARE_DELETE flag.
And the FILE_SHARE_DELETE flag cannot be used under Windows
95/98 (Bad Parameter). Which means, on those platforms, there
still doesn't appear to be a solution. Under NT/XP/2K,
AllocateFile() will have to modified to call CreateFile()
instead of fopen(). I'm not sure about ME, but I suspect it
behaves similarly to 95/98.
Mike Mascari
mascarm@mascari.com
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Stephan Szabo wrote:
> On Fri, 20 Sep 2002, Mike Mascari wrote:
......@@ -9278,42 +8762,6 @@ mascarm@mascari.com
From tgl@sss.pgh.pa.us Fri Sep 20 10:28:40 2002
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To: Stephan Szabo <sszabo@megazone23.bigpanda.com>
cc: Mike Mascari <mascarm@mascari.com>, Bruce Momjian <pgman@candle.pha.pa.us>,
PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] Win32 rename()/unlink() questions
In-Reply-To: <20020919224718.H36366-100000@megazone23.bigpanda.com>
References: <20020919224718.H36366-100000@megazone23.bigpanda.com>
Comments: In-reply-to Stephan Szabo <sszabo@megazone23.bigpanda.com>
message dated "Thu, 19 Sep 2002 22:50:36 -0700"
Date: Fri, 20 Sep 2002 10:27:52 -0400
Message-ID: <16067.1032532072@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
Status: OR
Stephan Szabo <sszabo@megazone23.bigpanda.com> writes:
> ... let you do the replace and keep reading (at the penalty that
> you've now got to have a way to know when to remove the
> various <something>s)
That is the hard part. Mike's description omitted one crucial step:
6. The old "foo" goes away when the last open file handle for it is
closed.
I doubt there is any practical way for Postgres to cause that to happen
if the OS itself does not have any support for it.
regards, tom lane
From pgsql-hackers-owner+M29205@postgresql.org Fri Sep 20 10:36:48 2002
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Stephan Szabo <sszabo@megazone23.bigpanda.com> writes:
> ... let you do the replace and keep reading (at the penalty that
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I don't think we are not going to be supporting Win9X so there isn't an
......@@ -9459,84 +8907,33 @@ Mike Mascari wrote:
> CreateFile() via fopen() but with no opportunity through the
> standard C library routines to use the FILE_SHARE_DELETE flag.
> And the FILE_SHARE_DELETE flag cannot be used under Windows
> 95/98 (Bad Parameter). Which means, on those platforms, there
> still doesn't appear to be a solution. Under NT/XP/2K,
> AllocateFile() will have to modified to call CreateFile()
> instead of fopen(). I'm not sure about ME, but I suspect it
> behaves similarly to 95/98.
>
> Mike Mascari
> mascarm@mascari.com
>
>
>
>
>
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--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073
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From mascarm@mascari.com Fri Sep 20 10:57:31 2002
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Date: Fri, 20 Sep 2002 10:57:00 -0400
From: Mike Mascari <mascarm@mascari.com>
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To: Bruce Momjian <pgman@candle.pha.pa.us>
cc: Stephan Szabo <sszabo@megazone23.bigpanda.com>,
PostgreSQL-development
<pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] Win32 rename()/unlink() questions
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Bruce Momjian wrote:
> I don't think we are not going to be supporting Win9X so there isn't an
> issue there. We will be supporting Win2000/NT/XP.
> 95/98 (Bad Parameter). Which means, on those platforms, there
> still doesn't appear to be a solution. Under NT/XP/2K,
> AllocateFile() will have to modified to call CreateFile()
> instead of fopen(). I'm not sure about ME, but I suspect it
> behaves similarly to 95/98.
>
> I don't understand FILE_SHARE_DELETE. I read the description at:
> Mike Mascari
> mascarm@mascari.com
>
> http://msdn.microsoft.com/library/default.asp?url=/library/en-us/fileio/base/createfile.asp
>
> but I don't understand it:
>
> FILE_SHARE_DELETE - Windows NT/2000/XP: Subsequent open operations on
> the object will succeed only if delete access is requested.
I think that's a rather poor description. I think it just means
that if the file is opened once via CreateFile() with
FILE_SHARE_DELETE, then any subsequent CreateFile() calls will
fail unless they too have FILE_SHARE_DELETE. In other words, if
one of us can delete this file while its open, any of us can.
Mike Mascari
mascarm@mascari.com
>
>
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--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073
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From pgsql-hackers-owner+M29208@postgresql.org Fri Sep 20 11:30:26 2002
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Bruce Momjian wrote:
> I don't think we are not going to be supporting Win9X so there isn't an
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Mike Mascari wrote:
> Bruce Momjian wrote:
......@@ -9676,73 +9073,6 @@ I don't understand what that gets us.
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073
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Date: Fri, 20 Sep 2002 08:10:19 -0700 (PDT)
From: Stephan Szabo <sszabo@megazone23.bigpanda.com>
To: Mike Mascari <mascarm@mascari.com>
cc: Bruce Momjian <pgman@candle.pha.pa.us>,
PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] Win32 rename()/unlink() questions
In-Reply-To: <3D8B373C.7060102@mascari.com>
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On Fri, 20 Sep 2002, Mike Mascari wrote:
> Bruce Momjian wrote:
> > I don't think we are not going to be supporting Win9X so there isn't an
> > issue there. We will be supporting Win2000/NT/XP.
> >
> > I don't understand FILE_SHARE_DELETE. I read the description at:
> >
> > http://msdn.microsoft.com/library/default.asp?url=/library/en-us/fileio/base/createfile.asp
> >
> > but I don't understand it:
> >
> > FILE_SHARE_DELETE - Windows NT/2000/XP: Subsequent open operations on
> > the object will succeed only if delete access is requested.
>
> I think that's a rather poor description. I think it just means
> that if the file is opened once via CreateFile() with
> FILE_SHARE_DELETE, then any subsequent CreateFile() calls will
> fail unless they too have FILE_SHARE_DELETE. In other words, if
> one of us can delete this file while its open, any of us can.
The question is, what happens if two people have the file open
and one goes and tries to delete it? Can the other still read
from it?
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On Fri, 20 Sep 2002, Mike Mascari wrote:
......@@ -9797,49 +9127,6 @@ and one goes and tries to delete it? Can the other still read
from it?
From JanWieck@Yahoo.com Fri Sep 20 11:36:53 2002
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Bruce Momjian <pgman@candle.pha.pa.us>,
PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] Win32 rename()/unlink() questions
References: <20020919230827.A36505-100000@megazone23.bigpanda.com> <3D8ACA96.80504@mascari.com>
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Mike Mascari wrote:
> instead of fopen(). I'm not sure about ME, but I suspect it
> behaves similarly to 95/98.
I just checked with Katie and the good news (tm) is that the Win32 port
we did here at PeerDirect doesn't support 95/98 and ME anyway. It does
support NT4, 2000 and XP. So don't bother.
Jan
--
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From pgsql-hackers-owner+M29216@postgresql.org Fri Sep 20 11:45:47 2002
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Mike Mascari wrote:
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Stephan Szabo wrote:
> On Fri, 20 Sep 2002, Mike Mascari wrote:
......@@ -9986,132 +9273,6 @@ mascarm@mascari.com
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From mascarm@mascari.com Fri Sep 20 11:55:47 2002
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Date: Fri, 20 Sep 2002 11:54:52 -0400
From: Mike Mascari <mascarm@mascari.com>
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To: Stephan Szabo <sszabo@megazone23.bigpanda.com>
cc: Bruce Momjian <pgman@candle.pha.pa.us>,
PostgreSQL-development
<pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] Win32 rename()/unlink() questions
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Stephan Szabo wrote:
> On Fri, 20 Sep 2002, Mike Mascari wrote:
>
>
>>I think that's a rather poor description. I think it just means
>>that if the file is opened once via CreateFile() with
>>FILE_SHARE_DELETE, then any subsequent CreateFile() calls will
>>fail unless they too have FILE_SHARE_DELETE. In other words, if
>>one of us can delete this file while its open, any of us can.
>
>
> The question is, what happens if two people have the file open
> and one goes and tries to delete it? Can the other still read
> from it?
Yes. I just tested it and it worked. I'll test Bruce's scenario
as well:
foo contains: "FOO"
bar contains: "BAR"
1. Process 1 opens "foo"
2. Process 2 opens "foo"
3. Process 1 calls MoveFile("foo", "foo2");
4. Process 3 opens "foo" <- Successful?
5. Process 1 calls MoveFile("bar", "foo");
6. Process 4 opens "foo" <- Successful?
7. Process 1 calls DeleteFile("foo2");
8. Process 1, 2, 3, 4 all read from their respective handles.
I think the thing to worry about is a race condition between the
two MoveFile() attempts. A very ugly hack would be to loop in a
CreateFile() in an attempt to open "foo", giving up if the error
is not a NOT EXISTS error code.
Mike Mascari
mascarm@mascari.com
From mascarm@mascari.com Fri Sep 20 12:29:18 2002
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Date: Fri, 20 Sep 2002 12:27:32 -0400
From: Mike Mascari <mascarm@mascari.com>
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To: PostgreSQL-development <pgsql-hackers@postgresql.org>
cc: Stephan Szabo <sszabo@megazone23.bigpanda.com>,
Bruce Momjian
<pgman@candle.pha.pa.us>
Subject: Re: [HACKERS] Win32 rename()/unlink() questions
References: <20020920080949.H40440-100000@megazone23.bigpanda.com> <3D8B44CC.6070802@mascari.com>
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I wrote:
> Stephan Szabo wrote:
>>
>> The question is, what happens if two people have the file open
>> and one goes and tries to delete it? Can the other still read
>> from it?
>
> Yes. I just tested it and it worked. I'll test Bruce's scenario as well:
>
> foo contains: "FOO"
> bar contains: "BAR"
>
> 1. Process 1 opens "foo"
> 2. Process 2 opens "foo"
> 3. Process 1 calls MoveFile("foo", "foo2");
> 4. Process 3 opens "foo" <- Successful?
> 5. Process 1 calls MoveFile("bar", "foo");
> 6. Process 4 opens "foo" <- Successful?
> 7. Process 1 calls DeleteFile("foo2");
> 8. Process 1, 2, 3, 4 all read from their respective handles.
Process 1: "FOO"
Process 2: "FOO"
Process 3: Error - File does not exist
Process 4: "BAR"
Its interesting in that it allows for Unix-style rename() and
unlink() behavior, but with a race condition. Without Stephan's
two MoveFile() trick and the FILE_SHARE_DELETE flag, however,
the result would be Access Denied. Are the places in the backend
that use rename() and unlink() renaming and unlinking files that
are only opened for a brief moment by other backends?
Mike Mascari
mascarm@mascari.com
From pgsql-hackers-owner+M29230@postgresql.org Fri Sep 20 13:12:45 2002
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I wrote:
> Stephan Szabo wrote:
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Mike Mascari wrote:
> Its interesting in that it allows for Unix-style rename() and
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Mike Mascari wrote:
> > foo contains: "FOO"
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It is good that moving the file out of the way works, but it doesn't
......@@ -10475,7 +9636,7 @@ Comments: In-reply-to Bruce Momjian <pgman@candle.pha.pa.us>
Date: Fri, 20 Sep 2002 11:50:17 -0400
Message-ID: <16739.1032537017@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
Status: ORr
Status: ROr
Bruce Momjian <pgman@candle.pha.pa.us> writes:
> I think we may be best just looping on MoveFileEx() until is succeeds.
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Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.us> writes:
......
doc/src/sgml/runtime.sgml
View file @ 27330595
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.180 2003/05/15 15:50:18 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.181 2003/05/23 16:34:36 momjian Exp $
-->
<Chapter Id="runtime">
......@@ -1858,16 +1858,6 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
</listitem>
</varlistentry>
<varlistentry>
<term><varname>STATEMENT_TIMEOUT</varname> (<type>integer</type>)</term>
<listitem>
<para>
Aborts any statement that takes over the specified number of
milliseconds. A value of zero turns off the timer.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>SHARED_BUFFERS</varname> (<type>integer</type>)</term>
<listitem>
......@@ -1958,6 +1948,16 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
</listitem>
</varlistentry>
<varlistentry>
<term><varname>STATEMENT_TIMEOUT</varname> (<type>integer</type>)</term>
<listitem>
<para>
Aborts any statement that takes over the specified number of
milliseconds. A value of zero turns off the timer.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>SUPERUSER_RESERVED_CONNECTIONS</varname>
(<type>integer</type>)</term>
......
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