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Re: 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: Re: Hot standby and b-tree killed items
Date: 2008-12-19 10:24:52
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
Simon Riggs wrote:
> We have infrastructure in place to make this work correctly, just need
> to add latestRemovedXid field to xl_btree_vacuum. So that part is easily
> solved.

That's tricky because there's no xmin/xmax on index tuples. You could 
conservatively use OldestXmin as latestRemovedXid, but that could stall 
the WAL redo a lot more than necessary. Or you could store 
latestRemovedXid in the page header, but that would need to be 
WAL-logged to ensure that it's valid after crash. Or you could look at 
the heap to fetch the xmin/xmax, but that would be expensive.

   Heikki Linnakangas

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