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Hot standby and b-tree killed items

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Hot standby and b-tree killed items
Date: 2008-12-19 08:49:02
Message-ID: 494B5FFE.4090909@enterprisedb.com (view raw or flat)
Thread:
Lists: pgsql-hackers
Whenever a B-tree index scan fetches a heap tuple that turns out to be 
dead, the B-tree item is marked as killed by calling _bt_killitems. When 
the page gets full, all the killed items are removed by calling 
_bt_vacuum_one_page.

That's a problem for hot standby. If any of the killed b-tree items 
point to a tuple that is still visible to a running read-only 
transaction, we have the same situation as with vacuum, and have to 
either wait for the read-only transaction to finish before applying the 
WAL record or kill the transaction.

It looks like there's some cosmetic changes related to that in the 
patch, the signature of _bt_delitems is modified, but there's no actual 
changes that would handle that situation. I didn't see it on the TODO on 
the hot standby wiki either. Am I missing something, or the patch?

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com

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