From: | "David E(dot) Wheeler" <david(at)justatheory(dot)com> |
---|---|
To: | Pg Hackers <pgsql-hackers(at)postgreSQL(dot)org> |
Subject: | Advisory Lock BIGINT Values |
Date: | 2012-03-10 00:36:08 |
Message-ID: | 69AC7BDF-4AA8-46FF-A6D9-8BD6FDB5A859@justatheory.com |
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Lists: | pgsql-hackers |
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) << 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,
Best,
DAvid
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