some intelligence (serial # style), so our node IDs were around
20000000.
Looks like a unique ID collision avoidance technique. Presumably you
can't really put lot of restraints on Slony tables themselves and
guarantee synchronicity (did i really just say that?)
# select * from _cores_minnesota_2.sl_rowid_seq ;
sequence_name | last_value | increment_by | max_value |
min_value | cache_value | log_cnt | is_cycled | is_called
---------------+------------------+--------------+---------------------+---
sl_rowid_seq | 2000000000000000 | 1 | 9223372036854775807 |
1 | 1 | 0 | f | t
(1 row)
Well, an 8 digit number going by your scheme at max: 99999999 *
1000000000000000 is well > max(int8) which is 9223372036854775808
$ echo 1000000000000000 | wc -c
17
Where I work, that value seems completely arbitrary (Chris?) so feel free
to change it. Also, where I'm at, I use a similar scheme for mapping
POSIX UIDs into Windows NT UUIDs in Samba/LDAP.
The assumption here is very small Node IDs, which is bollocks if you're
running more than one slon(8) instance on a machine your logs will fill
with many unreadable messages from different slon(8) PIDs that do not have
unique node IDs.
~BAS
---------
$ more src/backend/slony1_funcs.sql
[...snip[
create or replace function @[EMAIL PROTECTED] (int4, text)
returns int4
as '
declare
p_local_node_id alias for $1;
p_comment alias for $2;
v_old_node_id int4;
v_first_log_no int4;
v_event_seq int8;
begin
-- ----
-- Grab the central configuration lock
-- ----
lock table @[EMAIL PROTECTED];
-- ----
-- Make sure this node is uninitialized or got reset
-- ----
select last_value::int4 into v_old_node_id from
@[EMAIL PROTECTED];
if v_old_node_id != -1 then
raise exception ''Slony-I: This node is already
initialized'';
end if;
-- ----
-- Set sl_local_node_id to the requested value and add our
-- own system to sl_node.
-- ----
perform setval(''@[EMAIL PROTECTED]'', p_local_node_id);
perform setval(''@[EMAIL PROTECTED]'',
p_local_node_id::int8 *
''1000000000000000''::int8);
perform @[EMAIL PROTECTED] (p_local_node_id, p_comment,
false);
return p_local_node_id;
end;
' language plpgsql;
comment on function @[EMAIL PROTECTED] (int4, text) is
'no_id - Node ID #
no_comment - Human-oriented comment
I didn't expect that to be a problem, since it's certainly small enough
to fit in an int, but slonik gave a rather cryptic error:
<stdin>:974: PGRES_FATAL_ERROR select "_clustername".initializeLocalNode(20000000, 'Local
Slave node'); select "_clustername".enableNode_int(20000000); - ERROR: bigint out of range
CONTEXT: SQL statement "SELECT setval('"_clustername".sl_rowid_seq', $1 ::int8 *
'1000000000000000'::int8)"
PL/pgSQL function "initializelocalnode" line 26 at perform
Which makes it appear as if the node ID is being multiplied by one
quadrillion before attempting to stuff it into a BIGINT. when I set
the node ID down to single-digits, the error stopped.
--
Bill Moran
Collaborative Fusion Inc.
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l8*
-lava (Brian A. Seklecki - Pittsburgh, PA, USA)
http://www.spiritual-machines.org/
"...from back in the heady days when "helpdesk" meant nothing, "diskquota"
meant everything, and lives could be bought and sold for a couple of pages
of laser printout - and frequently were."
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