sqoop 增量导入追加模式，带时间戳列

有人可以帮助我了解 sqoop 增量中追加模式和最后修改模式之间的确切区别吗？

当可以使用附加模式（使用 --check-column 作为时间戳）完成相同的操作时，lastmodified 的需要是什么。它的工作原理相同，并且也会导入更新和插入的记录。

1. 模式：追加可用于您知道最后一个值的列。
2. 模式：lastmodified 模式可用于时间戳列。可能很难记住上次修改的时间戳。如果您知道上次修改的时间戳，则可以使用第一种方法。

模式：追加

mysql> describe emp;
+--------+--------------+------+-----+---------+-------+
| Field  | Type         | Null | Key | Default | Extra |
+--------+--------------+------+-----+---------+-------+
| id     | int(11)      | YES  |     | NULL    |       |
| name   | varchar(100) | YES  |     | NULL    |       |
| deg    | varchar(100) | YES  |     | NULL    |       |
| salary | int(11)      | YES  |     | NULL    |       |
| dep    | varchar(10)  | YES  |     | NULL    |       |
+--------+--------------+------+-----+---------+-------+
5 rows in set (0.00 sec)

使用 sqoop 命令导入数据。

sqoop import \
--connect jdbc:mysql://quickstart:3306/retail_db \
--username retail_dba \
--password cloudera \
-m 3 \
--table emp \
--split-by id \
--columns id,name,deg \
--warehouse-dir /user/sqoop/ \
--delete-target-dir \
--as-textfile

HDFS输出

[cloudera@quickstart lib]$ hadoop fs -ls -R /user/sqoop/
drwxr-xr-x   - cloudera supergroup          0 2017-12-02 13:14 /user/sqoop/emp
-rw-r--r--   1 cloudera supergroup          0 2017-12-02 13:14 /user/sqoop/emp/_SUCCESS
-rw-r--r--   1 cloudera supergroup         70 2017-12-02 13:14 /user/sqoop/emp/part-m-00000
-rw-r--r--   1 cloudera supergroup         64 2017-12-02 13:14 /user/sqoop/emp/part-m-00001
-rw-r--r--   1 cloudera supergroup         86 2017-12-02 13:14 /user/sqoop/emp/part-m-00002


mysql> select * from emp;
+------+---------+--------------+--------+------+
| id   | name    | deg          | salary | dep  |
+------+---------+--------------+--------+------+
| 1201 | gopal   | manager      |  50000 | tp   |
| 1202 | manisha | Proof reader |  50000 | TP   |
| 1203 | php dev | TECH WRITER  |  50000 | AC   |
| 1204 | Nilesh  | Domino dev   |  70000 | AF   |
| 1205 | Vinayak | Java dev     |  50000 | IT   |
| 1206 | Amish   | Cog dev      |  60000 | IT   |
| 1207 | Jatin   | Oracel dev   |  40001 | IT   |
| 1208 | Viren   | Java dev     |  70004 | IT   |
| 1209 | Ashish  | Oracel dev   |  40001 | IT   |
| 1210 | Satish  | Java dev     |  70004 | IT   |
+------+---------+--------------+--------+------+
10 rows in set (0.00 sec)

将新记录插入表中。

mysql> insert into emp values(1211,'Jag', 'be', 20000, 'IT');
Query OK, 1 row affected (0.03 sec)

mysql> select * from emp;
+------+---------+--------------+--------+------+
| id   | name    | deg          | salary | dep  |
+------+---------+--------------+--------+------+
| 1201 | gopal   | manager      |  50000 | tp   |
| 1202 | manisha | Proof reader |  50000 | TP   |
| 1203 | php dev | TECH WRITER  |  50000 | AC   |
| 1204 | Nilesh  | Domino dev   |  70000 | AF   |
| 1205 | Vinayak | Java dev     |  50000 | IT   |
| 1206 | Amish   | Cog dev      |  60000 | IT   |
| 1207 | Jatin   | Oracel dev   |  40001 | IT   |
| 1208 | Viren   | Java dev     |  70004 | IT   |
| 1209 | Ashish  | Oracel dev   |  40001 | IT   |
| 1210 | Satish  | Java dev     |  70004 | IT   |
| 1211 | Jag     | be           |  20000 | IT   |
+------+---------+--------------+--------+------+
11 rows in set (0.00 sec)

增量导入命令

sqoop import \
--connect jdbc:mysql://quickstart:3306/retail_db \
--username retail_dba \
--password cloudera \
--table emp \
--split-by id \
--check-column id \
--incremental append \
--last-value 1210 \
--warehouse-dir /user/sqoop/ \
--as-textfile

导入后

[cloudera@quickstart lib]$ hadoop fs -ls -R /user/sqoop/emp
-rw-r--r--   1 cloudera supergroup          0 2017-12-02 13:14 /user/sqoop/emp/_SUCCESS
-rw-r--r--   1 cloudera supergroup         70 2017-12-02 13:14 /user/sqoop/emp/part-m-00000
-rw-r--r--   1 cloudera supergroup         64 2017-12-02 13:14 /user/sqoop/emp/part-m-00001
-rw-r--r--   1 cloudera supergroup         86 2017-12-02 13:14 /user/sqoop/emp/part-m-00002
-rw-r--r--   1 cloudera cloudera           21 2017-12-02 13:48 /user/sqoop/emp/part-m-00003
[cloudera@quickstart lib]$ hadoop fs -cat /user/sqoop/emp/part-m-00003
1211,Jag,be,20000,IT

模式：最后修改

mysql> describe orders;

+-------------------+-------------+------+-----+---------+----------------+

| Field             | Type        | Null | Key | Default | Extra          |

+-------------------+-------------+------+-----+---------+----------------+

| order_id          | int(11)     | NO   | PRI | NULL    | auto_increment |

| order_date        | datetime    | NO   |     | NULL    |                |

| order_customer_id | int(11)     | NO   |     | NULL    |                |

| order_status      | varchar(45) | NO   |     | NULL    |                |

+-------------------+-------------+------+-----+---------+----------------+

4 rows in set (0.00 sec)    

将订单导入hdfs

sqoop import \
--connect jdbc:mysql://quickstart:3306/retail_db \
--username retail_dba \
--password cloudera \
--table orders \
--split-by order_id  \
--target-dir /user/sqoop/orders \
--as-textfile

导入后

[cloudera@quickstart lib]$ hadoop fs -ls -R /user/sqoop/orders
-rw-r--r--   1 cloudera supergroup          0 2017-12-02 16:01 /user/sqoop/orders/_SUCCESS
-rw-r--r--   1 cloudera supergroup     741597 2017-12-02 16:01 /user/sqoop/orders/part-m-00000
-rw-r--r--   1 cloudera supergroup     753022 2017-12-02 16:01 /user/sqoop/orders/part-m-00001
-rw-r--r--   1 cloudera supergroup     752368 2017-12-02 16:01 /user/sqoop/orders/part-m-00002
-rw-r--r--   1 cloudera supergroup     752940 2017-12-02 16:01 /user/sqoop/orders/part-m-00003

更新订单数据

mysql> select * from orders where order_id=10;
+----------+---------------------+-------------------+-----------------+
| order_id | order_date          | order_customer_id | order_status    |
+----------+---------------------+-------------------+-----------------+
|       10 | 2013-07-25 00:00:00 |              5648 | PENDING_PAYMENT |
+----------+---------------------+-------------------+-----------------+
1 row in set (0.00 sec)

mysql> update orders set order_status='CLOSED', order_date=now() where order_id=10;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from orders where order_id=10;
+----------+---------------------+-------------------+--------------+
| order_id | order_date          | order_customer_id | order_status |
+----------+---------------------+-------------------+--------------+
|       10 | 2017-12-02 16:19:23 |              5648 | CLOSED       |
+----------+---------------------+-------------------+--------------+
1 row in set (0.00 sec)

导入附加数据

sqoop import \
--connect jdbc:mysql://quickstart:3306/retail_db \
--username retail_dba \
--password cloudera \
--table orders \
--split-by order_id  \
--check-column order_date \
--merge-key order_id \
--incremental lastmodified \
--target-dir /user/sqoop/orders1 \
--as-textfile

Output

[cloudera@quickstart lib]$ hadoop fs -ls -R /user/sqoop/orders1
-rw-r--r--   1 cloudera cloudera          0 2017-12-02 16:07 /user/sqoop/orders1/_SUCCESS
-rw-r--r--   1 cloudera cloudera    2999918 2017-12-02 16:07 /user/sqoop/orders1/part-r-00000

Note:如果我们使用与之前相同的目录（订单），则会删除旧文件并创建新部分。