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Date: Thu, 11 Aug 2022 17:40:52 +0700
From: r.zharkov@postgrespro.ru
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Andrew Dunstan <andrew@dunslane.net>, Michael Paquier
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Subject: Re: Checking pgwin32_is_junction() errors
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On 2022-08-11 07:55, Thomas Munro wrote:
>> I checked a few variants:
>> 
>> 21.07.2022  15:11    <JUNCTION>     HOME [\??\Volume{GUID}\]
>> 09.08.2022  15:06    <JUNCTION>     Test1 [\\?\Volume{GUID}\]
>> 09.08.2022  15:06    <JUNCTION>     Test2 [\\.\Volume{GUID}\]
>> 09.08.2022  15:17    <JUNCTION>     Test3 [\??\Volume{GUID}\]
>> 09.08.2022  15:27    <JUNCTION>     Test4 [C:\temp\1]
>> 09.08.2022  15:28    <JUNCTION>     Test5 [C:\HOME\Temp\1]
> 
> One more thing I wondered about, now that we're following junctions
> outside PGDATA: can a junction point to another junction?  If so, I
> didn't allow for that: stat() gives up after one hop, because I
> figured that was enough for the stuff we expect inside PGDATA and I
> couldn't find any evidence in the man pages that referred to chains.
> But if you *are* allowed to create a junction "c:\huey" that points to
> junction "c:\dewey" that points to "c:\louie", and then you do initdb
> -D c:\huey\pgdata, then I guess it would fail.  Would you mind
> checking if that is a real possibility, and if so, testing this
> chain-following patch to see if it fixes it?

I made some junctions and rechecked both patches.

11.08.2022  16:11    <JUNCTION>     donald [C:\huey]
11.08.2022  13:23    <JUNCTION>     huey [C:\dewey]
11.08.2022  13:23    <JUNCTION>     dewey [C:\louie]
11.08.2022  16:57    <DIR>          louie

With the small attached patch initdb succeeded in any of these
"directories". If the junction chain is too long, initdb fails with
"could not create directory" as expected.

initdb -D huey/pgdata
...
Success.

initdb -N -D donald
...
Success.

11.08.2022  17:32    <DIR>          1
11.08.2022  17:32    <JUNCTION>     2 [C:\1]
11.08.2022  17:32    <JUNCTION>     3 [C:\2]
11.08.2022  17:32    <JUNCTION>     4 [C:\3]
11.08.2022  17:32    <JUNCTION>     5 [C:\4]
11.08.2022  17:32    <JUNCTION>     6 [C:\5]
11.08.2022  17:32    <JUNCTION>     7 [C:\6]
11.08.2022  17:32    <JUNCTION>     8 [C:\7]
11.08.2022  17:32    <JUNCTION>     9 [C:\8]
11.08.2022  17:32    <JUNCTION>     10 [C:\9]

initdb -D 10/pgdata
...
creating directory 10/pgdata ... initdb: error: could not create 
directory "10": File exists

initdb -D 9/pgdata
...
Success.

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