From: Bruce Momjian <bruce@momjian.us>
Message-Id: <200803061850.m26Ioaw26516@momjian.us>
Subject: Re: [GENERAL] advisory locks: documentation hint and feature request
In-Reply-To: 
 <CA896D7906BF224F8A6D74A1B7E54AB301750D0E@JENMAIL01.ad.intershop.net>
To: Marc Mamin <M.Mamin@intershop.de>
Date: Thu, 6 Mar 2008 13:50:36 -0500 (EST)
CC: PostgreSQL-documentation <pgsql-docs@postgresql.org>
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Marc Mamin wrote:
> doing this, I missed an information in the documentation that would be
> useful to add:
>  
>  
> pg_locks columns definition
> ---------------------------
>  
> current definition:
>  
> objid : OID of the object within its system catalog, 
>         or NULL if the object is not a general database object
>         
> to add: "For advisory locks it is used to distinguish  the two key
> spaces (one int8 or two int4 keys)
> 
> 
> Table 9-56. Advisory Lock Functions (8.3 Beta)
> -----------------------------------
>  current: (note that these two key spaces do not overlap)
>  
>  to add: "; The two key spaces are separated on the column objid in the
> pg_locks view"
>  

I have added your suggested changes to the docs with the attached patch.
Thanks.

>  Moreover I missed some function that would allow a cleaner
> implementation of my features 
>  (reducing the need to query the pg_locks view)
>  
>  For example:
>   
>  --current shared lock count (owned / all)
>  pg_advisory_lock_shared_count_my(key bigint)
>  pg_advisory_lock_shared_count_all(key bigint)
>  
>  
>  --enforce exclusive locks so that they cannot be stacked
>  pg_try_advisory_lock_single(key bigint)

Sorry, I am afraid they would not have general-enough usefulness.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://postgres.enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +

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Index: doc/src/sgml/catalogs.sgml
===================================================================
RCS file: /cvsroot/pgsql/doc/src/sgml/catalogs.sgml,v
retrieving revision 2.161
diff -c -c -r2.161 catalogs.sgml
*** doc/src/sgml/catalogs.sgml	31 Jan 2008 18:40:02 -0000	2.161
--- doc/src/sgml/catalogs.sgml	6 Mar 2008 18:48:54 -0000
***************
*** 5691,5697 ****
        <entry>any OID column</entry>
        <entry>
         OID of the object within its system catalog, or NULL if the
!        object is not a general database object
        </entry>
       </row>
       <row>
--- 5691,5700 ----
        <entry>any OID column</entry>
        <entry>
         OID of the object within its system catalog, or NULL if the
!        object is not a general database object.
!        For advisory locks it is used to distinguish the two key
!        spaces (<literal>1</> for an int8 key, <literal>2</> for two
!        int4 keys).
        </entry>
       </row>
       <row>
Index: doc/src/sgml/func.sgml
===================================================================
RCS file: /cvsroot/pgsql/doc/src/sgml/func.sgml,v
retrieving revision 1.422
diff -c -c -r1.422 func.sgml
*** doc/src/sgml/func.sgml	3 Mar 2008 18:09:02 -0000	1.422
--- doc/src/sgml/func.sgml	6 Mar 2008 18:48:58 -0000
***************
*** 12378,12384 ****
     <para>
      <function>pg_advisory_lock</> locks an application-defined resource,
      which can be identified either by a single 64-bit key value or two
!     32-bit key values (note that these two key spaces do not overlap).  If
      another session already holds a lock on the same resource, the
      function will wait until the resource becomes available.  The lock
      is exclusive.  Multiple lock requests stack, so that if the same resource
--- 12378,12385 ----
     <para>
      <function>pg_advisory_lock</> locks an application-defined resource,
      which can be identified either by a single 64-bit key value or two
!     32-bit key values (note that these two key spaces do not overlap). 
!     The key type is specified in <literal>pg_locks.objid</>.  If
      another session already holds a lock on the same resource, the
      function will wait until the resource becomes available.  The lock
      is exclusive.  Multiple lock requests stack, so that if the same resource

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