Re: Advisory Lock BIGINT Values

On Fri, Mar 9, 2012 at 04:36:08PM -0800, David E. Wheeler wrote:
> Hackers,
>
> The documentation for pg_locks says that, for BIGINT advisory locks:
>
> > A bigint key is displayed with its high-order half in the classid column, its low-order half in the objid column
>
> I was in need of knowing what the bigint is that is waiting on a lock, and Andrew Dunstan was kind enough to help me out with that. Since other folks might also need it, here’s a doc patch.
>
> diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
> new file mode 100644
> index 9564e01..de1c266
> *** a/doc/src/sgml/catalogs.sgml
> --- b/doc/src/sgml/catalogs.sgml
> ***************
> *** 7313,7319 ****
> A <type>bigint</type> key is displayed with its
> high-order half in the <structfield>classid</> column, its low-order half
> in the <structfield>objid</> column, and <structfield>objsubid</> equal
> ! to 1. Integer keys are displayed with the first key in the
> <structfield>classid</> column, the second key in the <structfield>objid</>
> column, and <structfield>objsubid</> equal to 2. The actual meaning of
> the keys is up to the user. Advisory locks are local to each database,
> --- 7313,7322 ----
> A <type>bigint</type> key is displayed with its
> high-order half in the <structfield>classid</> column, its low-order half
> in the <structfield>objid</> column, and <structfield>objsubid</> equal
> ! to 1. The original <type>bigint</type> value can be reassembled with the
> ! expression <literal>(classid::int::bit(64) &lt;&lt; 32 |
> ! objid::int::bit(64))::bigint</literal>. Integer keys are displayed with the
> ! first key in the
> <structfield>classid</> column, the second key in the <structfield>objid</>
> column, and <structfield>objsubid</> equal to 2. The actual meaning of
> the keys is up to the user. Advisory locks are local to each database,

Thanks, applied.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +