#namespace("PgSql")
    #sql("getSinglePk")
    select pg_constraint.conname as pk_name,pg_attribute.attname as colname,pg_type.typname as typename from
    pg_constraint  inner join pg_class
    on pg_constraint.conrelid = pg_class.oid
    inner join pg_attribute on pg_attribute.attrelid = pg_class.oid
    and  pg_attribute.attnum = pg_constraint.conkey[1]
    inner join pg_type on pg_type.oid = pg_attribute.atttypid
    where pg_class.relname = #para(table_name)
    and pg_constraint.contype='p'
    #end
#end