Обсуждение: Why use " != "

""ipig"" <ipig@ercist.iscas.ac.cn> wrote
>
>    in postgresql-8.1.3/src/backend/storage/lmgr/proc.c
>    there are 2 function InitProcess and InitDummyProcess, both use
> " if (MyProc != NULL)
>      elog(ERROR, "you already exist");  " (line 215 and 315)
>
>    why use " != " ?
>

I guess you misread "exist" to "exit"? Try to change "!=" to whatever you
think of, and see what will happen.

Regards,
Qingqing

    It done so, because InitProcess() is supposed to be called only
once per backend, because it allocates a PGPROC from a LIST OF free
PGPROCs.
   So with this test, and calling elog( ERROR, ... ) we are stopping
the caller from doing a second initialization for this backend.

On 5/16/06, ipig <ipig@ercist.iscas.ac.cn> wrote:
>
>
> Hi,
>
>    in postgresql-8.1.3/src/backend/storage/lmgr/proc.c
>    there are 2 function InitProcess and InitDummyProcess, both use
> " if (MyProc != NULL)
>      elog(ERROR, "you already exist");  " (line 215 and 315)
>
>    why use " != " ?
>
> Best regards.
>
>

As Qingqing Zhou said, i misread "exist". 
Thanks.

----- Original Message ----- 
From: "Gurjeet Singh" <singh.gurjeet@gmail.com>
To: "ipig" <ipig@ercist.iscas.ac.cn>
Cc: <pgsql-hackers@postgresql.org>
Sent: Tuesday, May 16, 2006 11:36 AM
Subject: Re: [HACKERS] Why use " != "

   It done so, because InitProcess() is supposed to be called only
once per backend, because it allocates a PGPROC from a LIST OF free
PGPROCs.
   So with this test, and calling elog( ERROR, ... ) we are stopping
the caller from doing a second initialization for this backend.

On 5/16/06, ipig <ipig@ercist.iscas.ac.cn> wrote:
>
>
> Hi,
>
>    in postgresql-8.1.3/src/backend/storage/lmgr/proc.c
>    there are 2 function InitProcess and InitDummyProcess, both use
> " if (MyProc != NULL)
>      elog(ERROR, "you already exist");  " (line 215 and 315)
>
>    why use " != " ?
>
> Best regards.
>
>

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