Re: Allow cancelling VACUUM of nbtrees with corrupted right links

On Wed, Jun 27, 2018 at 12:18 PM, Andres Freund <andres@anarazel.de> wrote:
> It's possibly wrong that it's unreachable - I've just not managed to get
> there. If somebody has an idea how to build a reproducible case to reach
> it...

Set a breakpoint in _bt_unlink_halfdead_page() after the initial
"LockBuffer(leafbuf, BUFFER_LOCK_UNLOCK);", and then provoke a page
split in the left sibling by carefully inserting values that belong
within its part of the key space? I would probably attempt this with
an index on text, so that I could contrive as many key values that
belong on the left sibling as needed.

You're probably looking at a test-case that doesn't involve a
multi-level deletion, where the leaf and target page are the same. Not
sure if you want to reproduce the multi-level deletion case
independently.


-- 
Peter Geoghegan