hive 文件系統學習實例

Hive存儲是基于hadoop hdfs文件系統的，通過默認內嵌的Derby 數據庫或外部數據庫系統（如mysql)組織元數據訪問，下面就通過實際案例描述其存儲過程。

1， 在hive 中創建表，然后把外部csv文件導入其中（外部文件為Batting.csv, 內部表為temp_batting):

hive>create table temp_batting(col_value STRING);

hive> show tables;
OK
temp_batting
...

hive>LOAD DATAINPATH'hive/data/Batting.csv' OVERWRITE INTO TABLE temp_batting;

2, 查看外部mysql數據庫，可以看到新創建的temp_batting表：

mysql> use hive;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

mysql> select * from TBLS;
+--------+-------------+-------+------------------+-------+-----------+-------+--------------+----------------+--------------------+--------------------+
| TBL_ID | CREATE_TIME | DB_ID | LAST_ACCESS_TIME | OWNER | RETENTION | SD_ID |TBL_NAME     | TBL_TYPE       | VIEW_EXPANDED_TEXT |VIEW_ORIGINAL_TEXT |
+--------+-------------+-------+------------------+-------+-----------+-------+--------------+----------------+--------------------+----------
|     66 |  1432707070 |     1 |               0 | root  |        0 |    66 | temp_batting | MANAGED_TABLE  |NULL               | NULL              |
|               |
+--------+-------------+-------+------------------+-------+-----------+-------+--------------+----------------+--------------------+----------

...

查看其在hdfs上存儲路徑：

mysql> select * from SDS;
+-------+-------+--------------------------------------------------+---------------+---------------------------+--------------------------------------------------------+-------------+------------------------------------------------------------+----------+
| SD_ID | CD_ID | INPUT_FORMAT                                    |IS_COMPRESSED | IS_STOREDASSUBDIRECTORIES | LOCATION                                             | NUM_BUCKETS |OUTPUT_FORMAT                                            | SERDE_ID |
+-------+-------+--------------------------------------------------+---------------+---------------------------+--------------------------------
|    66 |    71 | org.apache.hadoop.mapred.TextInputFormat        |              |                          |hdfs://localhost:9000/user/hive/warehouse/temp_batting |         -1 |org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat |      66 |

可以看到是:
hdfs://localhost:9000/user/hive/warehouse/temp_batting

3，到hadoop 的hdfs文件系統中查看這個表路徑：

[root@lr rli]# hadoop dfs -ls /user/hive/warehouse
DEPRECATED: Use of this script to execute hdfs command is deprecated.
Instead use the hdfs command for it.
...

drwxr-xr-x   - root supergroup          02015-05-27 14:16 /user/hive/warehouse/temp_batting
...

[root@lr rli]# hadoop dfs -ls/user/hive/warehouse/temp_batting

DEPRECATED: Use of this script to execute hdfs command isdeprecated.
Instead use the hdfs command for it.


Found 1 items
-rwxr-xr-x   1 root supergroup    6398990 2015-05-2714:02 /user/hive/warehouse/temp_batting/Batting.csv

可以看到其文件大小及內容。

結論：

Hive通過關聯數據庫系統記錄文件的存儲路徑，屬性等，實際數據存在hdfs系統中，當通過select等操作生成相應的map/reduce進程進一步數據分析處理。