RE: reloption to prevent VACUUM from truncating empty pages at theend of relation

From: Julien Rouhaud [mailto:rjuju123@gmail.com]
> FWIW, I prefer shrink over truncate, though I'd rather go with
> vacuum_shink_enabled as suggested previously.

Thanks.  I'd like to leave a committer to choose the name.  FWIW, I chose shrink_enabled rather than
vacuum_shrink_enabledbecause this property may be used in other shrink situations in the future.  What I imagined was
thatwith the zheap, DELETE or some maintenance operation, not vacuum, may try to shrink the table.  I meant this
propertyto indicate "whether this table shrinks or not" regardless of the specific operation that can shrink the
table.



> I'm not sure that I get this comment.  Since both require a
> ShareUpdateExclusiveLock, you can't change the parameter while a
> VACUUM is active on that table.  Did you wanted to use another lock
> mode?

No, changing the parameter acquires ShareUpdaeExclusive lock.  I just imitated the description for n_distinct in the
samecomment block.  The meaning is that the setting cannot be changed during VACUUM, so in-flight VACUUM is not
affected.


Regards
Takayuki Tsunakawa