mysql和pgsql夸库查询插入

       当mysql中用到pgsql表的垮库操作时，首先可以使用ETL是可以解决的，今天学习了一种代码处理方式解决方案。

insert_sql = <<-sql
          insert into #{audience_attributes_table}
          select opxpid, "c", array_to_string(jx_array_sort(madlib.array_agg(pretargeting_id)), ',')
          from (
            select mt.opxpid as opxpid, ap.pretargeting_id as pretargeting_id
            from #{master_table} mt
            inner join
            #{map_audiences_pretargetings}
            on mt.hash_value = ap.audience_id
            where mt.hash_key = 'aids'
            and mt.hash_value in (#{aids.uniq.join(",")})
            group by 1,2
          ) m
          group by 1, 2;
        sql

#拼装查询结果。

def map_audiences_pretargetings
        pids = Pretargeting.find(:all, :select => :id, :conditions => ["start_date <= ? AND end_date >= ? AND approval_status = ?", Date.today + 3.days, Date.today - 3.days, true])
        adjustments = AudiencesPretargeting.find_all_by_pretargeting_id(pids.collect(&:id)).collect{|ad_pg| [ad_pg.pretargeting_id,ad_pg.audience_id]}

        adjustments_flattened = adjustments.map{ |adj| ",(#{adj[0]}, #{adj[1]})" }
        "(
             VALUES
             (0, 0)
             #{adjustments_flattened.join}
         ) AS ap (pretargeting_id, audience_id)"
end