+ def pk_and_sequence_for(table)
+ # First try looking for a sequence with a dependency on the
+ # given table's primary key.
+ result = query(<<-end_sql, 'PK and serial sequence')[0]
+ SELECT attr.attname, seq.relname
+ FROM pg_class seq,
+ pg_attribute attr,
+ pg_depend dep,
+ pg_namespace name,
+ pg_constraint cons
+ WHERE seq.oid = dep.objid
+ AND seq.relkind = 'S'
+ AND attr.attrelid = dep.refobjid
+ AND attr.attnum = dep.refobjsubid
+ AND attr.attrelid = cons.conrelid
+ AND attr.attnum = cons.conkey[1]
+ AND cons.contype = 'p'
+ AND dep.classid = '"pg_class"'::regclass
+ AND dep.refclassid = '"pg_class"'::regclass
+ AND dep.refobjid = '#{quote_table_name(table)}'::regclass
+ end_sql
+
+ if result.nil? or result.empty?
+ # If that fails, try parsing the primary key's default value.
+ # Support the 7.x and 8.0 nextval('foo'::text) as well as
+ # the 8.1+ nextval('foo'::regclass).
+ result = query(<<-end_sql, 'PK and custom sequence')[0]
+ SELECT attr.attname,
+ CASE
+ WHEN split_part(def.adsrc, '''', 2) ~ '.' THEN
+ substr(split_part(def.adsrc, '''', 2),
+ strpos(split_part(def.adsrc, '''', 2), '.')+1)
+ ELSE split_part(def.adsrc, '''', 2)
+ END
+ FROM pg_class t
+ JOIN pg_attribute attr ON (t.oid = attrelid)
+ JOIN pg_attrdef def ON (adrelid = attrelid AND adnum = attnum)
+ JOIN pg_constraint cons ON (conrelid = adrelid AND adnum = conkey[1])
+ WHERE t.oid = '#{quote_table_name(table)}'::regclass
+ AND cons.contype = 'p'
+ AND def.adsrc ~* 'nextval'
+ end_sql
+ end
+
+ # [primary_key, sequence]