数据仓库最常碰到的扩展是给一个已经存在的维度表和事实表添加列。本节说明如何在客户维度表和销售订单事实表上添加列，并在新列上应用SCD2，以及对定时装载脚本所做的修改。假设需要在客户维度中增加送货地址属性，并在销售订单事实表中增加数量度量值。
先看一下增加列时模式发生的变化。
修改后源数据库模式如下图所示。
修改后DW数据库模式如下图所示。
1. 修改数据库模式
使用下面的SQL脚本修改源数据库模式。
USE source;使用下面的HiveQL脚本修改RDS数据库模式。
ALTER TABLE customer
ADD shipping_address VARCHAR(50) AFTER customer_state
, ADD shipping_zip_code INT AFTER shipping_address
, ADD shipping_city VARCHAR(30) AFTER shipping_zip_code
, ADD shipping_state VARCHAR(2) AFTER shipping_city ;
ALTER TABLE sales_order
ADD order_quantity INT AFTER order_amount ;
USE rds;ALTER TABLE customer ADD COLUMNS (shipping_address VARCHAR(50) COMMENT 'shipping_address', shipping_zip_code INT COMMENT 'shipping_zip_code', shipping_city VARCHAR(30) COMMENT 'shipping_city', shipping_state VARCHAR(2) COMMENT 'shipping_state') ;ALTER TABLE sales_order ADD COLUMNS (order_quantity INT COMMENT 'order_quantity') ;使用下面的HiveQL脚本修改DW数据库模式。
USE dw;-- 修改客户维度表ALTER TABLE customer_dim RENAME TO customer_dim_old;CREATE TABLE customer_dim ( customer_sk INT comment 'surrogate key', customer_number INT comment 'number', customer_name VARCHAR(50) comment 'name', customer_street_address VARCHAR(50) comment 'address', customer_zip_code INT comment 'zipcode', customer_city VARCHAR(30) comment 'city', customer_state VARCHAR(2) comment 'state', shipping_address VARCHAR(50) COMMENT 'shipping_address', shipping_zip_code INT COMMENT 'shipping_zip_code', shipping_city VARCHAR(30) COMMENT 'shipping_city', shipping_state VARCHAR(2) COMMENT 'shipping_state', version INT comment 'version', effective_date DATE comment 'effective date', expiry_date DATE comment 'expiry date') CLUSTERED BY (customer_sk) INTO 8 BUCKETS STORED AS ORC TBLPROPERTIES ('transactional'='true');INSERT INTO customer_dim SELECT customer_sk, customer_number, customer_name, customer_street_address, customer_zip_code, customer_city, customer_state, NULL, NULL, NULL, NULL, version, effective_date, expiry_date FROM customer_dim_old;DROP TABLE customer_dim_old;-- 修改销售订单事实表ALTER TABLE sales_order_fact RENAME TO sales_order_fact_old;CREATE TABLE sales_order_fact ( order_sk INT comment 'order surrogate key', customer_sk INT comment 'customer surrogate key', product_sk INT comment 'product surrogate key', order_date_sk INT comment 'date surrogate key', order_amount DECIMAL(10 , 2 ) comment 'order amount', order_quantity INT COMMENT 'order_quantity')CLUSTERED BY (order_sk) INTO 8 BUCKETSSTORED AS ORC TBLPROPERTIES ('transactional'='true');INSERT INTO sales_order_fact SELECT *,NULL FROM sales_order_fact_old;DROP TABLE sales_order_fact_old;
上面这段代码中修改DW数据库模式这部分很奇怪：明明可以直接在表上添加列，为何要新建一个表，再把数据装载到新表中去呢？原因是老版本的Hive对ORC格式表的模式修改尤其是增加列的支持有很多问题，只有通过新建表并重新组织数据的方式才能正常执行。看一下面的简单例子就会一目了然。
use test; drop table if exists t1;create table t1(c1 int, c2 string) clustered by (c1) into 8 buckets stored as orc TBLPROPERTIES ('transactional'='true'); insert into t1 values (1,'aaa'); alter table t1 add columns (c3 string) ;update t1 set c2='ccc' where c1=1;select * from t1; 上面的代码建了一个ORC表，插入一行数据，添加一列，修改数据，最后再查询数据。这些在关系数据库中很普通的操作，最后一步查询居然出错，如下图所示。
这个例子是在Hive1.1.0上执行的，jira上说2.0.0修复了ORC表模式修改的问题，可以参考以下链接的说明：
https://issues.apache.org/jira/browse/HIVE-11981
注意，在低版本的Hive上修改ORC表的模式，特别是增加列时一定要慎重。当数据量很大时，这会是一个相当费时并会占用大量空间的操作。
2. 重建Sqoop作业
使用下面的脚本重建Sqoop作业，增加order_quantity列。
last_value=`sqoop job --show myjob_incremental_import --meta-connect jdbc:hsqldb:hsql://cdh2:16000/sqoop | grep incremental.last.value | awk '{print $3}'`sqoop job --delete myjob_incremental_import --meta-connect jdbc:hsqldb:hsql://cdh2:16000/sqoopsqoop job \--meta-connect jdbc:hsqldb:hsql://cdh2:16000/sqoop \--create myjob_incremental_import \-- \import \--connect "jdbc:mysql://cdh1:3306/source?useSSL=false&user=root&password=mypassword" \--table sales_order \--columns "order_number, customer_number, product_code, order_date, entry_date, order_amount, order_quantity" \--hive-import \--hive-table rds.sales_order \--incremental append \--check-column order_number \--last-value $last_value
其中$last_value是上次ETL执行后，被检查列的最大值。
3. 修改定期装载regular_etl.sql文件
修改数据库模式后，还要修改已经使用的定期装载HiveQL脚本。修改后的脚本如下所示。
-- 设置变量以支持事务set hive.support.concurrency=true;set hive.exec.dynamic.partition.mode=nonstrict;set hive.txn.manager=org.apache.hadoop.hive.ql.lockmgr.DbTxnManager;set hive.compactor.initiator.on=true;set hive.compactor.worker.threads=1;USE dw; -- 设置SCD的生效时间和过期时间SET hivevar:cur_date = CURRENT_DATE();SET hivevar:pre_date = DATE_ADD(${hivevar:cur_date},-1);SET hivevar:max_date = CAST('2200-01-01' AS DATE); -- 设置CDC的上限时间INSERT OVERWRITE TABLE rds.cdc_time SELECT last_load, ${hivevar:cur_date} FROM rds.cdc_time;-- 装载customer维度-- 设置已删除记录和地址相关列上SCD2的过期，用<=>运算符处理NULL值。UPDATE customer_dim SET expiry_date = ${hivevar:pre_date} WHERE customer_dim.customer_sk IN (SELECT a.customer_sk FROM (SELECT customer_sk, customer_number, customer_street_address, customer_zip_code, customer_city, customer_state, shipping_address, shipping_zip_code, shipping_city, shipping_state FROM customer_dim WHERE expiry_date = ${hivevar:max_date}) a LEFT JOIN rds.customer b ON a.customer_number = b.customer_number WHERE b.customer_number IS NULL OR ( !(a.customer_street_address <=> b.customer_street_address) OR !(a.customer_zip_code <=> b.customer_zip_code) OR !(a.customer_city <=> b.customer_city) OR !(a.customer_state <=> b.customer_state) OR !(a.shipping_address <=> b.shipping_address) OR !(a.shipping_zip_code <=> b.shipping_zip_code) OR !(a.shipping_city <=> b.shipping_city) OR !(a.shipping_state <=> b.shipping_state) )); -- 处理customer_street_addresses列上SCD2的新增行 INSERT INTO customer_dimSELECT ROW_NUMBER() OVER (ORDER BY t1.customer_number) + t2.sk_max, t1.customer_number, t1.customer_name, t1.customer_street_address, t1.customer_zip_code, t1.customer_city, t1.customer_state, t1.shipping_address, t1.shipping_zip_code, t1.shipping_city, t1.shipping_state, t1.version, t1.effective_date, t1.expiry_dateFROM ( SELECT t2.customer_number customer_number, t2.customer_name customer_name, t2.customer_street_address customer_street_address, t2.customer_zip_code customer_zip_code, t2.customer_city customer_city, t2.customer_state customer_state, t2.shipping_address shipping_address, t2.shipping_zip_code shipping_zip_code, t2.shipping_city shipping_city, t2.shipping_state shipping_state, t1.version + 1 version, ${hivevar:pre_date} effective_date, ${hivevar:max_date} expiry_date FROM customer_dim t1 INNER JOIN rds.customer t2 ON t1.customer_number = t2.customer_number AND t1.expiry_date = ${hivevar:pre_date} LEFT JOIN customer_dim t3 ON t1.customer_number = t3.customer_number AND t3.expiry_date = ${hivevar:max_date} WHERE (!(t1.customer_street_address <=> t2.customer_street_address) OR !(t1.customer_zip_code <=> t2.customer_zip_code) OR !(t1.customer_city <=> t2.customer_city) OR !(t1.customer_state <=> t2.customer_state) OR !(t1.shipping_address <=> t2.shipping_address) OR !(t1.shipping_zip_code <=> t2.shipping_zip_code) OR !(t1.shipping_city <=> t2.shipping_city) OR !(t1.shipping_state <=> t2.shipping_state) ) AND t3.customer_sk IS NULL) t1 CROSS JOIN (SELECT COALESCE(MAX(customer_sk),0) sk_max FROM customer_dim) t2;-- 处理customer_name列上的SCD1-- 因为hive的update的set子句还不支持子查询，所以这里使用了一个临时表存储需要更新的记录，用先delete再insert代替update-- 因为SCD1本身就不保存历史数据，所以这里更新维度表里的所有customer_name改变的记录，而不是仅仅更新当前版本的记录DROP TABLE IF EXISTS tmp;CREATE TABLE tmp ASSELECT a.customer_sk, a.customer_number, b.customer_name, a.customer_street_address, a.customer_zip_code, a.customer_city, a.customer_state, a.shipping_address, a.shipping_zip_code, a.shipping_city, a.shipping_state, a.version, a.effective_date, a.expiry_date FROM customer_dim a, rds.customer b WHERE a.customer_number = b.customer_number AND !(a.customer_name <=> b.customer_name); DELETE FROM customer_dim WHERE customer_dim.customer_sk IN (SELECT customer_sk FROM tmp); INSERT INTO customer_dim SELECT * FROM tmp;-- 处理新增的customer记录 INSERT INTO customer_dimSELECT ROW_NUMBER() OVER (ORDER BY t1.customer_number) + t2.sk_max, t1.customer_number, t1.customer_name, t1.customer_street_address, t1.customer_zip_code, t1.customer_city, t1.customer_state, t1.shipping_address, t1.shipping_zip_code, t1.shipping_city, t1.shipping_state, 1, ${hivevar:pre_date}, ${hivevar:max_date}FROM ( SELECT t1.* FROM rds.customer t1 LEFT JOIN customer_dim t2 ON t1.customer_number = t2.customer_number WHERE t2.customer_sk IS NULL) t1 CROSS JOIN (SELECT COALESCE(MAX(customer_sk),0) sk_max FROM customer_dim) t2;-- 装载product维度-- 设置已删除记录和product_name、product_category列上SCD2的过期UPDATE product_dim SET expiry_date = ${hivevar:pre_date} WHERE product_dim.product_sk IN (SELECT a.product_sk FROM (SELECT product_sk,product_code,product_name,product_category FROM product_dim WHERE expiry_date = ${hivevar:max_date}) a LEFT JOIN rds.product b ON a.product_code = b.product_code WHERE b.product_code IS NULL OR (a.product_name <> b.product_name OR a.product_category <> b.product_category));-- 处理product_name、product_category列上SCD2的新增行 INSERT INTO product_dimSELECT ROW_NUMBER() OVER (ORDER BY t1.product_code) + t2.sk_max, t1.product_code, t1.product_name, t1.product_category, t1.version, t1.effective_date, t1.expiry_dateFROM ( SELECT t2.product_code product_code, t2.product_name product_name, t2.product_category product_category, t1.version + 1 version, ${hivevar:pre_date} effective_date, ${hivevar:max_date} expiry_date FROM product_dim t1 INNER JOIN rds.product t2 ON t1.product_code = t2.product_code AND t1.expiry_date = ${hivevar:pre_date} LEFT JOIN product_dim t3 ON t1.product_code = t3.product_code AND t3.expiry_date = ${hivevar:max_date} WHERE (t1.product_name <> t2.product_name OR t1.product_category <> t2.product_category) AND t3.product_sk IS NULL) t1 CROSS JOIN (SELECT COALESCE(MAX(product_sk),0) sk_max FROM product_dim) t2;-- 处理新增的product记录INSERT INTO product_dimSELECT ROW_NUMBER() OVER (ORDER BY t1.product_code) + t2.sk_max, t1.product_code, t1.product_name, t1.product_category, 1, ${hivevar:pre_date}, ${hivevar:max_date}FROM ( SELECT t1.* FROM rds.product t1 LEFT JOIN product_dim t2 ON t1.product_code = t2.product_code WHERE t2.product_sk IS NULL) t1 CROSS JOIN (SELECT COALESCE(MAX(product_sk),0) sk_max FROM product_dim) t2;-- 装载order维度INSERT INTO order_dimSELECT ROW_NUMBER() OVER (ORDER BY t1.order_number) + t2.sk_max, t1.order_number, t1.version, t1.effective_date, t1.expiry_date FROM(SELECT order_number order_number, 1 version, order_date effective_date, '2200-01-01' expiry_date FROM rds.sales_order, rds.cdc_time WHERE entry_date >= last_load AND entry_date < current_load ) t1CROSS JOIN (SELECT COALESCE(MAX(order_sk),0) sk_max FROM order_dim) t2;-- 装载销售订单事实表INSERT INTO sales_order_factSELECT order_sk, customer_sk, product_sk, date_sk, order_amount, order_quantity FROM rds.sales_order a, order_dim b, customer_dim c, product_dim d, date_dim e, rds.cdc_time f WHERE a.order_number = b.order_numberAND a.customer_number = c.customer_numberAND a.order_date >= c.effective_dateAND a.order_date < c.expiry_dateAND a.product_code = d.product_codeAND a.order_date >= d.effective_dateAND a.order_date < d.expiry_dateAND to_date(a.order_date) = e.dateAND a.entry_date >= f.last_load AND a.entry_date < f.current_load ;-- 更新时间戳表的last_load字段INSERT OVERWRITE TABLE rds.cdc_time SELECT current_load, current_load FROM rds.cdc_time;
4. 测试
（1）执行下面的SQL脚本准备客户和销售订单测试数据。
USE source; /*** 客户数据的改变如下： 更新已有八个客户的送货地址 新增客户9 ***/ UPDATE customer SET shipping_address = customer_street_address , shipping_zip_code = customer_zip_code , shipping_city = customer_city , shipping_state = customer_state ; INSERT INTO customer (customer_name , customer_street_address , customer_zip_code , customer_city , customer_state , shipping_address , shipping_zip_code , shipping_city , shipping_state) VALUES ('Online Distributors' , '2323 Louise Dr.' , 17055 , 'Pittsburgh' , 'PA' , '2323 Louise Dr.' , 17055 , 'Pittsburgh' , 'PA') ; /*** 新增订单日期为2016年7月12日的9条订单。***/ SET @start_date := unix_timestamp('2016-07-12'); SET @end_date := unix_timestamp('2016-07-13'); DROP TABLE IF EXISTS temp_sales_order_data; CREATE TABLE temp_sales_order_data AS SELECT * FROM sales_order WHERE 1=0; SET @order_date := from_unixtime(@start_date + rand() * (@end_date - @start_date)); SET @amount := floor(1000 + rand() * 9000);SET @quantity := floor(10 + rand() * 90);INSERT INTO temp_sales_order_data VALUES (117, 1, 1, @order_date, @order_date, @amount, @quantity); SET @order_date := from_unixtime(@start_date + rand() * (@end_date - @start_date)); SET @amount := floor(1000 + rand() * 9000); SET @quantity := floor(10 + rand() * 90);INSERT INTO temp_sales_order_data VALUES (118, 2, 2, @order_date, @order_date, @amount, @quantity); SET @order_date := from_unixtime(@start_date + rand() * (@end_date - @start_date)); SET @amount := floor(1000 + rand() * 9000);SET @quantity := floor(10 + rand() * 90); INSERT INTO temp_sales_order_data VALUES (119, 3, 3, @order_date, @order_date, @amount, @quantity); SET @order_date := from_unixtime(@start_date + rand() * (@end_date - @start_date)); SET @amount := floor(1000 + rand() * 9000);SET @quantity := floor(10 + rand() * 90); INSERT INTO temp_sales_order_data VALUES (120, 4, 4, @order_date, @order_date, @amount, @quantity); SET @order_date := from_unixtime(@start_date + rand() * (@end_date - @start_date)); SET @amount := floor(1000 + rand() * 9000);SET @quantity := floor(10 + rand() * 90); INSERT INTO temp_sales_order_data VALUES (121, 5, 1, @order_date, @order_date, @amount, @quantity); SET @order_date := from_unixtime(@start_date + rand() * (@end_date - @start_date)); SET @amount := floor(1000 + rand() * 9000);SET @quantity := floor(10 + rand() * 90); INSERT INTO temp_sales_order_data VALUES (122, 6, 2, @order_date, @order_date, @amount, @quantity); SET @order_date := from_unixtime(@start_date + rand() * (@end_date - @start_date)); SET @amount := floor(1000 + rand() * 9000);SET @quantity := floor(10 + rand() * 90); INSERT INTO temp_sales_order_data VALUES (123, 7, 3, @order_date, @order_date, @amount, @quantity); SET @order_date := from_unixtime(@start_date + rand() * (@end_date - @start_date)); SET @amount := floor(1000 + rand() * 9000);SET @quantity := floor(10 + rand() * 90); INSERT INTO temp_sales_order_data VALUES (124, 8, 4, @order_date, @order_date, @amount, @quantity); SET @order_date := from_unixtime(@start_date + rand() * (@end_date - @start_date)); SET @amount := floor(1000 + rand() * 9000);SET @quantity := floor(10 + rand() * 90); INSERT INTO temp_sales_order_data VALUES (125, 9, 1, @order_date, @order_date, @amount, @quantity); INSERT INTO sales_order SELECT NULL,customer_number,product_code,order_date,entry_date,order_amount,order_quantity FROM temp_sales_order_data ORDER BY order_date; COMMIT ;
修改后的客户源数据如下图所示。
修改后的销售订单源数据如下图所示。
（2）执行定期装载并查看结果。
使用下面的命令执行定期装载。
./regular_etl.sh使用下面的查询验证结果。
use dw;select customer_number no, customer_name name, shipping_city, shipping_zip_code zip, shipping_state st, version ver, effective_date eff, expiry_date exp from customer_dim;已存在客户的新记录有了送货地址。老的（过期）记录没有。9号客户是新加的，具有送货地址。如下图所示。
select order_sk o_sk, customer_sk c_sk, product_sk p_sk, order_date_sk od_sk, order_amount amt, order_quantity qty from sales_order_factcluster by o_sk;只有9个订单有数量，老的销售数据没有。如下图所示。
select * from rds.cdc_time;时间戳表的最后装载日期已经更新。如下图所示。
至此，增加列所需的修改已完成。