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Re: Core team statement on replication in PostgreSQL - Mailing list pgsql-hackers

From Gurjeet Singh
Subject Re: Core team statement on replication in PostgreSQL
Date
Msg-id 65937bea0805301321x668b8b1fxe15d86243ee8fcaf@mail.gmail.com
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In response to Core team statement on replication in PostgreSQL  (Tom Lane <tgl@sss.pgh.pa.us>)
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On Thu, May 29, 2008 at 7:42 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
The big problem
is that long-running slave-side queries might still need tuples that are
vacuumable on the master, and so replication of vacuuming actions would
cause the slave's queries to deliver wrong answers.

Another issue with read-only slaves just popped up in my head.

How do we block the readers on the slave while it is replaying an ALTER TABLE or similar command that requires Exclusive lock and potentially alters the table's structure. Or does the WAL replay already takes an x-lock on such a table?

Best regards,
--
gurjeet[.singh]@EnterpriseDB.com
singh.gurjeet@{ gmail | hotmail | indiatimes | yahoo }.com

EnterpriseDB http://www.enterprisedb.com

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