Re: BUG #5487: dblink failed with 63 bytes connection names

From: Takahiro Itagaki <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>
To: pgsql-hackers(at)postgresql(dot)org
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #5487: dblink failed with 63 bytes connection names
Date: 2010-06-01 02:55:11
Message-ID: 20100601115511.95D2.52131E4D@oss.ntt.co.jp
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"Takahiro Itagaki" <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp> wrote:

> Bug reference: 5487
> Logged by: Takahiro Itagaki
> Email address: itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp
> Description: dblink failed with 63 bytes connection names
> Details:
>
> Contib/dblink module seems to have a bug in handling
> connection names in NAMEDATALEN-1 bytes.

Here is a patch to fix the bug. I think it comes from wrong usage
of snprintf(NAMEDATALEN - 1). It just copies 62 bytes + \0.

In addition, it should be safe to use pg_mbcliplen() to truncate
extra bytes in connection names because we might return invalid
text when a multibyte character is at 62 or 63 bytes.

Note that the fix should be ported to previous versions, too.

> It cannot use exiting connections with 63 bytes name
> in some cases. For example, we cannot disconnect
> such connections. Also, we can reconnect with the
> same name and will have two connections with the name.
>
> =# SELECT dblink_connect(repeat('1234567890', 6) || 'ABC',
> 'host=localhost');
> dblink_connect
> ----------------
> OK
> (1 row)
>
> =# SELECT dblink_get_connections();
> dblink_get_connections
> -------------------------------------------------------------------
> {123456789012345678901234567890123456789012345678901234567890ABC}
> (1 row)
>
> =# SELECT dblink_disconnect(repeat('1234567890', 6) || 'ABC');
> ERROR: connection
> "123456789012345678901234567890123456789012345678901234567890ABC" not
> available

Regards,
---
Takahiro Itagaki
NTT Open Source Software Center

Attachment Content-Type Size
dblink_63bytes.patch application/octet-stream 2.5 KB

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