[Pgpool-hackers] Partial replication

[Tatsuo Ishii]

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.
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese: http://www.sraoss.co.jp