Re: HOT is applied - Mailing list pgsql-hackers

From Pavan Deolasee
Subject Re: HOT is applied
Date
Msg-id 2e78013d0709211046t1001ccdcx23374eeadcb81ccb@mail.gmail.com
Whole thread Raw
In response to Re: HOT is applied  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers


On 9/21/07, Tom Lane <tgl@sss.pgh.pa.us> wrote:


I'm also starting to come around to liking the page-header-xid field
a bit more.  I suggest that it could replace the "page is prunable"
flag bit altogether --- to mark the page prunable, you must store
some appropriate xid into the header field.  This would avoid a useless
prune attempt immediately after a page is marked prunable.


Agree. I was thinking of minimum of the following:

1 xmin of INSERT_IN_PROGRESS tuple
2 xmax of DELETE_IN_PROGRESS tuple
3 xmax of RECENTLY_DEAD_TUPLE

When we attempt a prune, we can set xid to the minimum of the above
three. If none of the above tuples exist in the page, xid can be set to FrozenXid
A page need not be pruned if its xid is set to FrozenXid or is greater
than OldtestXmin.

In addition, I guess we can even set the xid also when we insert,
delete or update from the page unless its already set to a lower value.

Thanks,
Pavan

--
Pavan Deolasee
EnterpriseDB     http://www.enterprisedb.com

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