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使用UDW创建历史拉链表。

介绍

• 历史拉链表

  • 历史拉链表是一种数据模型，主要针对数据仓库设计中表存储数据的方式而定义的。**它记录一个事物从开始到当前状态的所有变化的信息。**拉链表可以避免按每一天存储所有记录造成的海量存储问题，同时也是处理缓慢变化数据的一种常见方式。
  • 也就是说，对于表中的任何数据，不进行真正的删除，只记录操作和有效日期。

• 流程

  • 
  • 其中，tmp0表有两个分区，表示历史数据和当前数据，使用tmp1对tmp0和事实表进行更新和交换。

  ​

操作

创建表

• 首先需要创建delta表，事实表，以及两个tmp表

• -- 事实表
  create table public.member_fatdt0
  (
      member_id varchar(64),         -- 会员ID
      phoneno varchar(20),           -- 电话号码
      dw_beg_date date,              -- 生效日期
      dw_end_date date,              -- 失效日期
      dtype char(1),                 -- 类型（历史数据，当前数据）
      dw_status char(1),             -- 数据操作类型（I，D，U）
      dw_ins_date date               -- 数据仓库插入日期
  )with(appendonly=true,compresslevel=5)   -- 压缩级别
  distributed by (member_id)
  PARTITION BY RANGE (dw_end_date)
  (
      PARTITION p20111201 START (date '2011-12-01') INCLUSIVE,
      PARTITION p20111202 START (date '2011-12-02') INCLUSIVE,
      PARTITION p20111203 START (date '2011-12-03') INCLUSIVE,
      PARTITION p20111204 START (date '2011-12-04') INCLUSIVE,
      PARTITION p20111205 START (date '2011-12-05') INCLUSIVE,
      PARTITION p20111206 START (date '2011-12-06') INCLUSIVE,
      PARTITION p20111207 START (date '2011-12-07') INCLUSIVE,
      PARTITION p20111231 START (date '2011-12-31') INCLUSIVE
      END (date '3001-01-01') EXCLUSIVE
  );
  
  -- 增量表
  create table public.member_delta
  (
      member_id varchar(64),
      phoneno varchar(20),
      action char(1),                      -- 数据操作类型（I，D，U）
      dw_ins_date date                     -- 类型（新增，删除，更新）
  )with(appendonly=true,compresslevel=5)   -- 压缩级别
  distributed by (member_id)
  
  -- 临时表
  create table public.member_tmp0
  (
      member_id varchar(64),
      phoneno varchar(20),
      dw_beg_date date,
      dw_end_date date,
      dtype char(1),
      dw_status char(1),
      dw_ins_date date
  )with(appendonly=true,compresslevel=5)   -- 压缩级别
  distributed by (member_id)
  PARTITION BY LIST (dtype)
  (
      PARTITION PHIS VALUES ('H'),      -- 表示历史信息
      PARTITION PCUR VALUES ('C'),      -- 表示当前信息
      DEFAULT PARTITION other
  );
  

  – 临时表1
  create table public.member_tmp1
  (
  member_id varchar(64),
  phoneno varchar(20),
  dw_beg_date date,
  dw_end_date date,
  dtype char(1),
  dw_status char(1),
  dw_ins_date date
  )with(appendonly=true,compresslevel=5) – 压缩级别
  distributed by (member_id)

• 

插入数据

• 插入delta表

  • Insert into member_delta values('mem006','1310000006','I','2011-12-03');
    Insert into member_delta values('mem002','1310000002','D','2011-12-03');
    Insert into member_delta values('mem003','1310000003','U','2011-12-03');
    

  
  - ![55252708610](http://wx4.sinaimg.cn/mw690/0060lm7Tly1g124h8xtgtj30al02w0sk.jpg)
  
  

• 插入事实表

  • Insert into member_fatdt0 values('mem001','1310000001','2011-12-01','3000-12-31','C','I','2011-12-02');
    Insert into member_fatdt0 values('mem002','1310000002','2011-12-01','3000-12-31','C','I','2011-12-02');
    Insert into member_fatdt0 values('mem003','1310000003','2011-12-01','3000-12-31','C','I','2011-12-02');
    Insert into member_fatdt0 values('mem004','1310000004','2011-12-01','3000-12-31','C','I','2011-12-02');
    Insert into member_fatdt0 values('mem004','1310000004','2011-12-01','3000-12-31','C','I','2011-12-02');
    Insert into member_fatdt0 values('mem005','1310000005','2011-12-01','3000-12-31','C','I','2011-12-02');
    

  • 

数据刷新

1. 将member_fatdt0表与member_delta左外连接，相关联的历史数据插入到member_tmp0历史分区，反之插入到member_tmp0的当前分区

   • 这里主要处理update和delete操作，若能进行左连接，说明数据有更新，插入历史分区

   • truncate table public.member_tmp0;
     -- 清理临时表
     insert into public.member_tmp0
     (
         member_id,
         phoneno,
         dw_beg_date,
         dw_end_date,
         dtype,
         dw_status,
         dw_ins_date
     )
     select a.member_id,a.phoneno,a.dw_beg_date,
             case when b.member_id is null then a.dw_end_date
             else date '2011-12-02'
             end as dw_end_date,
             case when b.member_id is null then 'C'
             else 'H'
             end as dtype,
             case when b.member_id is null then a.dw_status
             else b.action
             end as dw_status,
             date '2011-12-03'
     from public.member_fatdt0 a
     left join public.member_delta b 
     on a.member_id = b.member_id
     and b.action in('D','U')
     where a.dw_beg_date <= cast('2011-12-02' as date) -1
     and a.dw_end_date > cast('2011-12-02' as date)-1;
     

   • 

2. 将member_delta当前数据（更新，插入的新数据）插入到member_tmp0当前分区，end时间为无穷。

   • insert into public.member_tmp0
     (
         member_id,
         phoneno,
         dw_beg_date,
         dw_end_date,
         dtype,
         dw_status,
         dw_ins_date
     )
     select member_id,phoneno,
         cast('2011-12-02' as date),
         cast('3000-12-31' as date),
         'C',
         action,
         cast('2011-12-03' as date)
     from public.member_delta
     where action in ('I','U');
     
     

   • 

3. 将member_tmp0历史数据与member_fatdt0相应分区交换（通过member_tmp1表进行交换）。

   • alter table  member_tmp1 drop constraint member_tmp0_1_prt_phis_check;
     truncate table public.member_tmp1;
     alter table public.member_tmp0 exchange partition for ('H') with table public.member_tmp1;
     alter table public.member_fatdt0 exchange partition for('2011-12-02') with table public.member_tmp1;
     

     • 

4. 将member_tmp0当前数据与member_fatdt0相应分区交换（通过member_tmp1表进行交换）。

   • alter table  member_tmp1 drop constraint member_fatdt0_1_prt_p20111202_check
     alter table  member_tmp1 drop constraint member_tmp0_1_prt_pcur_check
     alter table public.member_tmp0 exchange partition for('C') with table public.member_tmp1;
     alter table public.member_fatdt0 exchange partition for('3000-12-31') with table public.member_tmp1;
     

   •