Re: Reviewing freeze map code

Andres Freund wrote:

> I'm looking into three approaches right now:
> 
> 3) Use WAL logging for the already_marked = true case.


> 3) This approach so far seems the best. It's possible to reuse the
> xl_heap_lock record (in an afaics backwards compatible manner), and in
> most cases the overhead isn't that large.  It's of course annoying to
> emit more WAL, but it's not that big an overhead compared to extending a
> file, or to toasting.  It's also by far the simplest fix.

I suppose it's fine if we crash midway from emitting this wal record and
the actual heap_update one, since the xmax will appear to come from an
aborted xid, right?

I agree that the overhead is probably negligible, considering that this
only happens when toast is invoked.  It's probably not as great when the
new tuple goes to another page, though.

-- 
Álvaro Herrera                http://www.2ndQuadrant.com/
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