Re: Inadequate thought about buffer locking during hot standby replay

On 12.11.2012 22:53, Tom Lane wrote:
> Here's an updated patch that fixes the GIST replay functions as well as
> the other minor issues that were mentioned.  Barring objections, I'll
> set about back-patching this as far as 9.0.

Ok. It won't help all that much on 9.0, though.

> One thing that could use verification is my fix for
> gistRedoPageSplitRecord.  AFAICS, the first page listed in the WAL
> record is always the "original" page, and the ones following it are
> pages that were split off from it, and can (as yet) only be reached by
> following right-links from the "original" page.  As such, it should be
> okay to release locks on the non-first pages as soon as we've written
> them.  We have to hold lock on the original page though to avoid letting
> readers follow dangling right-links.  Also, the update of
> NSN/FOLLOW_RIGHT on the child page (if any) has to be done atomically
> with all this, so that has to be done before releasing the original-page
> lock as well.  Does that sound right?

Yep.

- Heikki