pk_and_sequence_for

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 345
        def pk_and_sequence_for(table) #:nodoc:
          # First try looking for a sequence with a dependency on the
          # given table's primary key.
          result = query(            SELECT attr.attname, nsp.nspname, seq.relname            FROM pg_class      seq,                 pg_attribute  attr,                 pg_depend     dep,                 pg_constraint cons,                 pg_namespace  nsp            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 seq.relnamespace  = nsp.oid              AND cons.contype      = 'p'              AND dep.classid       = 'pg_class'::regclass              AND dep.refobjid      = '#{quote_table_name(table)}'::regclass, 'SCHEMA')[0]

          if result.nil? or result.empty?
            result = query(              SELECT attr.attname, nsp.nspname,                CASE                  WHEN pg_get_expr(def.adbin, def.adrelid) !~* 'nextval' THEN NULL                  WHEN split_part(pg_get_expr(def.adbin, def.adrelid), '''', 2) ~ '.' THEN                    substr(split_part(pg_get_expr(def.adbin, def.adrelid), '''', 2),                           strpos(split_part(pg_get_expr(def.adbin, def.adrelid), '''', 2), '.')+1)                  ELSE split_part(pg_get_expr(def.adbin, def.adrelid), '''', 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])              JOIN pg_namespace   nsp  ON (t.relnamespace = nsp.oid)              WHERE t.oid = '#{quote_table_name(table)}'::regclass                AND cons.contype = 'p'                AND pg_get_expr(def.adbin, def.adrelid) ~* 'nextval|uuid_generate', 'SCHEMA')[0]
          end

          pk = result.shift
          if result.last
            [pk, PostgreSQL::Name.new(*result)]
          else
            [pk, nil]
          end
        rescue
          nil
        end