I totally understand DDL taking exclusive locks, the problem here seems to be that the *SELECTs* are taking out exclusive locks, locking out the ALTER, which feels like a bug.
On Wednesday, January 29, 2014, Peter Eisentraut <pete...@gmx.net> wrote: > On 1/29/14, 4:59 PM, Neil Harkins wrote: > > Why are those exclusive locks present? > > Can't the database rely on mvcc for those reads > > without locking? The autocommit should be > > increasing the xid used for the reads, so the > > ALTER should be able to slip in-between? > > One would think so, but it's more complicated. There is a long thread > on pgsql-hackers spreading over many months that discusses the > intricacies of reducing the strength of the locks taken by DDL commands. > This is being addressed, but at the moment most DDL commands take > exclusive locks. > >
