On Thu, May 29, 2008 at 7:42 PM, Tom Lane <<a href="mailto:tgl@sss.pgh.pa.us">tgl@sss.pgh.pa.us</a>> wrote:<br
/><divclass="gmail_quote"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt
0pt0pt 0.8ex; padding-left: 1ex;"> The big problem<br /> is that long-running slave-side queries might still need
tuplesthat are<br /> vacuumable on the master, and so replication of vacuuming actions would<br /> cause the slave's
queriesto deliver wrong answers.</blockquote></div><br />Another issue with read-only slaves just popped up in my
head.<br/><br />How do we block the readers on the slave while it is replaying an ALTER TABLE or similar command that
requiresExclusive lock and potentially alters the table's structure. Or does the WAL replay already takes an x-lock on
sucha table?<br /><br clear="all" />Best regards,<br />-- <br />gurjeet[.singh]@EnterpriseDB.com<br />singh.gurjeet@{
gmail| hotmail | indiatimes | yahoo }.com<br /><br />EnterpriseDB <a
href="http://www.enterprisedb.com">http://www.enterprisedb.com</a><br/><br />Mail sent from my BlackLaptop device