On Mon, Aug 27, 2018 at 10:12 PM, Andres Freund <and...@anarazel.de> wrote: > Huh? Oids between, say, 1 and FirstNormalObjectId, are vastly more > common than the rest. And even after that, individual tables get large > clusters of sequential values to the global oid counter.
Sure, but if you get a large cluster of sequential values, a straight mod-N bucket mapping works just fine. I think the bigger problem is that you might get a large cluster of values separated by exactly a power of 2. For instance, say you have one serial column and one index: rhaas=# create table a (x serial primary key); CREATE TABLE rhaas=# create table b (x serial primary key); CREATE TABLE rhaas=# select 'a'::regclass::oid, 'b'::regclass::oid; oid | oid -------+------- 16422 | 16430 (1 row) If you have a lot of tables like that, bad things are going to happen to your hash table. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
