def pk_and_sequence_for(table)
execute("SELECT attr.attname, (name.nspname || '.' || seq.relname)\nFROM pg_class seq,\npg_attribute attr,\npg_depend dep,\npg_namespace name,\npg_constraint cons\nWHERE seq.oid = dep.objid\nAND seq.relnamespace = name.oid\nAND seq.relkind = 'S'\nAND attr.attrelid = dep.refobjid\nAND attr.attnum = dep.refobjsubid\nAND attr.attrelid = cons.conrelid\nAND attr.attnum = cons.conkey[1]\nAND cons.contype = 'p'\nAND dep.refobjid = '\#{table}'::regclass\n", 'Find pk sequence')[0]
rescue
nil
end