On Thu, Mar 10, 2022 at 7:13 PM Andres Freund <andres@anarazel.de> wrote:
> Large allocation can take a bit. Especially dead_item_alloc() sneakily
> initializes parallelism (which is darn ugly).
Attached v3 revision of the patch makes this a bit clearer.
The patch now moves the pg_class updates for indexes from the end of
lazy_scan_heap() to its heap_vacuum_rel() caller, at the point just
after lazy_scan_heap() returns. This seems logical to me because it
makes all pg_class updates take place inside heap_vacuum_rel(). It
also means that we pretty start parallel mode right at the beginning
of lazy_scan_heap(), and end it right at the end -- which also seems
like a small improvement.
And so we no longer end parallel mode in order to be able to safely
update pg_class for indexes. Rather, we end parallel mode because
processing by lazy_scan_heap() as a whole completed.
--
Peter Geoghegan
