On 13.12.2010 15:04, Robert Haas wrote:
On Mon, Dec 13, 2010 at 7:09 AM, Heikki Linnakangas
<heikki.linnakan...@enterprisedb.com> wrote:
Attached is an updated patch, but that issue with limited number of backup
blocks needs to be resolved. The straightforward way would be to change the
WAL format to increase the limit.
Eh, is that going to bloat WAL?
Nah. The way split now works is that:
1. Split the page. Write a WAL record with the contents of the page halves.
2. Insert the downlink pointers in the parent, and set the NSN and clear
F_FOLLOW_RIGHT flags on the child pages. A 2nd WAL record is written for
this.
In this new patch version, at step 2, the 2nd WAL record updates the
LSNs and takes full-page-images of the child pages if necessary.
Previous patches overlooked that. Usually a full page image won't be
necessary, because we just wrote the page-split WAL record at step 1 for
those pages. It's only if a checkpoint started between in the small
window between steps 1 and 2.
So this should have no effect on performance, but it is necessary for
correctness.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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