OK, I'm getting the above error on one of my fairly new 8.3 production databases. It happens when I run a query to see the size of my tables. SELECT pg_relation_size(c.relfilenode), n.nspname AS schemaname, c.relname AS tablename, pg_get_userbyid(c.relowner) AS tableowner, t.spcname AS tablespace, c.relhasindex AS hasindexes, c.relhasrules AS hasrules, c.reltriggers > 0 AS hastriggers FROM pg_class c LEFT JOIN pg_namespace n ON n.oid = c.relnamespace LEFT JOIN pg_tablespace t ON t.oid = c.reltablespace WHERE n.nspname = 'public'; ERROR: could not open relation with OID 49152 If I run this query: SELECT c.relfilenode, n.nspna... same as the above after this... I get this: relfilenode | schemaname | tablename | tableowner | tablespace | hasindexes | hasrules | hastriggers -------------+------------+----------------------------+------------+------------+------------+----------+------------- 49956 | public | paid_idx_pkey | dgish | | f | f | f 49958 | public | page_access_timestamp | dgish | | f | f | f 49152 | public | page_access | dgish | | t | f | f and a few other lines editted out for brevity. Any ideas what the cause of this is? What part of my catalogs is borked? Now, I can backup this db, and restore it with no errors, and the error will go away. Same query on the same dataset returns the right number of rows and their size.