Hi Josh,
Thanks for replying. Few questions.
a) If I change the sequence in postgres just like that, will that normally
affect the overall database design from the open source system? I mean will it
crash the system?
b) And when you do this?
CREATE SEQUENCE some_id_seq INCREMENT BY 2;
Will that sequence reflects to all tables automatically? Or just specific table?
I hope it's all tables. After all, the project table is dependent to many other
tables too.
c) If I follow your approach on updating the sequences, do I still run this
command?
bucardo add all sequences herd=therd
d) Lastly, for this command
SELECT setval('some_id_seq'::regclass, 104);
I assume I run this only once right?
However for new database from fresh, I can just ignore this. Correct?
e) Can bucardo do streaming replication? I mean always sync when there's data
changes?
Looking forward to hear from you soon.
Thank you.
> Date: Fri, 23 Aug 2013 10:16:07 -0600
> From: [email protected]
> To: [email protected]
> CC: [email protected]
> Subject: Re: [Bucardo-general] Replication problems? data overwritten?
>
> On Fri, Aug 23, 2013 at 02:30:55PM +0000, eric machine wrote:
> > ------------------------------
> > ID | UserID | Project
> > ---------------------------
> > 1 | John | A
> > 1 | Susan | X
> > 2 | John | B
> > 2 | Susan | Y
> > 3 | John | C
>
> The above can't happen, because ID is a primary key, so all values in that
> column must be unique, and not null. So you can't have two rows with the same
> ID value.
>
> > or at least this
> > HQ - project table
> > ------------------------------
> > ID | UserID | Project
> > ---------------------------
> > 1 | John | A
> > 2 | John | B
> > 3 | John | C
> > 4 | Susan | X
> > 5 | Susan | Y
>
> This won't work either, because Bucardo would have to change the ID values for
> you. It won't do that; a replication system that changes your data wouldn't be
> very useful.
>
> > Note: RubyReps doesn't have this problem. Why? When you enable
> > streaming replication, for dbleft the primary key will be
> > auto-increment based on odd number. For dbright, it will auto increment
> > on even number. Just I can't figure out how-to solve this on bucardo 5.
>
> Bucardo won't set that up for you, but that's exactly what you need to do
> here. When you're creating the sequences at first, you'd do something like
> this:
>
> CREATE SEQUENCE some_id_seq INCREMENT BY 2;
> ...and on the second database...
> CREATE SEQUENCE some_id_seq INCREMENT BY 2 START WITH 2;
>
> Since your sequences are already created, you'll need to change both of them
> like this:
>
> ALTER SEQUENCE whatever_id_seq INCREMENT BY 2;
>
> You'll also need to check the current values of the sequence in both
> databases, make sure one is even, one is odd, and both are larger than the
> maximum ID value already in the database. You can check the current value in
> each database with SELECT * FROM some_id_seq, which gives you something like
> this:
>
> josh=# select last_value from b_id_seq ;
> last_value
> ------------
> 13
> (1 row)
>
> Do that on both databases, and take the bigger one. Let's say it's 103. Then
> on HQ you'll do this:
>
> SELECT setval('some_id_seq'::regclass, 104);
>
> ... and on Branch, you'll do this:
>
> SELECT setval('some_id_seq'::regclass, 105);
>
> That way one sequence will generate odd values, and the other will generate
> odd values.
>
> --
> Josh Tolley [email protected] 801-987-0252
> End Point Corporation http://www.endpoint.com
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