[Pgpool-hackers] Partial replication

[Tatsuo Ishii]

> Le 18/02/2011 02:21, Tatsuo Ishii a écrit :
>> Hi hackes,
>> 
>> After my talk of pgpool-II V3 at FOSDEM 2011, I got a question about
>> the idea "partial replication", which allows to replicate part of
>> a database cluster in replication mode.
>> 
>> This has been on my personal TODO list for years, and I start to think
>> about the implementation design again.
>> 
>> - We could have "database level partial replication" and "table level
>>   partial replication".
>> 
>> - "Database level partial replication" is easy to do. Just having a
>>   list of databases to replicate (or not to replicate) and
>>   pool_where_to_send() will look it. However cross database tables
>>   such as pg_database must be always replicated.
>> 
>> - "Table level partial replication" is not so easy. In addition to
>>   having a list of tables to replicate (or not to replicate), we would
>>   want to have such a list for schemas.
>> 
>> - If we have such a schema list, we need to know which schema the
>>   table belogs to. This is not super easy if the table is not schema
>>   qualified but doable.
>> 
>> - Functions would be troublesome because we cannot know which table it
>>   is going to write.
>> 
>> Just my memorandum. Please feel free to add comments.
> 
> As you say, databases would be easy.
> 
> I don't see an easy way to configure table names. Using a text file
> would be a burden if the user has a big number of tables. If you want to
> have such a feature, we need to provide a way to easyly configure the
> replication feature. We already have a system DB available. We could
> probably use it to "register" the tables to replicate.

Year to store large configuration data, we could use PostgreSQL
itself. One thing I want to do is, getting ride of system DB. We could
use one of DB nodes for this purpose, no?

Another problem we have to resolve is, online recovery. Probably we
need to wait for the day when PostgreSQL can do the base backup
partialy.
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese: http://www.sraoss.co.jp