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📜 Impala-Shell

📅 最后修改于: 2020-11-30 04:59:00 🧑 作者: Mango

在前面的章节中，我们已经看到了使用cloudera及其架构来安装Impala。

Impala Shell(命令提示符)
色相(用户界面)
ODBC和JDBC(第三方库)

本章介绍如何启动Impala Shell以及Shell的各种选项。

Impala Shell命令参考

Impala shell的命令分为通用命令，查询特定选项以及表和数据库特定选项，如下所述。

通用命令

帮帮我
版
历史
壳(或)！
连接
退出退出

查询特定选项

设置/取消
个人资料
说明

表和数据库特定的选项

改变
描述
下降
插入
选择
显示
用

启动Impala Shell

打开cloudera终端，以超级用户身份登录，然后如下所示输入cloudera作为密码。

[cloudera@quickstart ~]$ su
Password: cloudera
[root@quickstart cloudera]#

通过键入以下命令来启动Impala shell-

[root@quickstart cloudera] # impala-shell 
Starting Impala Shell without Kerberos authentication 
Connected to quickstart.cloudera:21000 
Server version: impalad version 2.3.0-cdh5.5.0 RELEASE 
(build 0c891d79aa38f297d244855a32f1e17280e2129b)
********************************************************************* 

Welcome to the Impala shell. Copyright (c) 2015 Cloudera, Inc. All rights reserved.
(Impala Shell v2.3.0-cdh5.5.0 (0c891d7) built on Mon Nov 9 12:18:12 PST 2015)

Want to know what version of Impala you're connected to? Run the VERSION command to 
find out! 
********************************************************************* 
[quickstart.cloudera:21000] >

Impala –通用命令

下面解释了Impala的通用命令-

帮助命令

Impala shell的help命令为您提供了Impala中可用命令的列表-

[quickstart.cloudera:21000] > help;
 
Documented commands (type help ):
========================================================
compute  describe  insert  set     unset  with  version
connect  explain   quit    show    values use
exit     history   profile select  shell  tip 
  
Undocumented commands:
========================================= 
alter create desc drop help load summary

版本命令

version命令为您提供了Impala的当前版本，如下所示。

[quickstart.cloudera:21000] > version;
Shell version: Impala Shell v2.3.0-cdh5.5.0 (0c891d7) built on Mon Nov 9 
12:18:12 PST 2015

Server version: impalad version 2.3.0-cdh5.5.0 RELEASE (build 
0c891d79aa38f297d244855a32f1e17280e2129b)

历史命令

Impala的history命令显示在shell中执行的最后10条命令。以下是history命令的示例。在这里，我们执行了5个命令，分别是版本，帮助，显示，使用和历史。

[quickstart.cloudera:21000] > history;
[1]:version;
[2]:help;
[3]:show databases;
[4]:use my_db;
[5]:history;

退出/退出命令

您可以使用quit或exit命令退出Impala shell，如下所示。

[quickstart.cloudera:21000] > exit; 
Goodbye cloudera

连接命令

connect命令用于连接到Impala的给定实例。如果您未指定任何实例，则它将连接到默认端口21000 ，如下所示。

[quickstart.cloudera:21000] > connect; 
Connected to quickstart.cloudera:21000 
Server version: impalad version 2.3.0-cdh5.5.0 RELEASE (build 
0c891d79aa38f297d244855a32f1e17280e2129b)

Impala查询特定选项

Impala的查询特定命令接受查询。它们在下面解释-

说明

说明命令返回给定查询的执行计划。

[quickstart.cloudera:21000] > explain select * from sample;
Query: explain select * from sample
+------------------------------------------------------------------------------------+ 
| Explain String                                                                     | 
+------------------------------------------------------------------------------------+ 
| Estimated Per-Host Requirements: Memory = 48.00MB VCores = 1                       | 
| WARNING: The following tables are missing relevant table and/or column statistics. |
| my_db.customers                                                                    | 
| 01:EXCHANGE [UNPARTITIONED]                                                        | 
| 00:SCAN HDFS [my_db.customers]                                                     | 
| partitions = 1/1 files = 6 size = 148B                                             | 
+------------------------------------------------------------------------------------+ 
Fetched 7 row(s) in 0.17s

个人资料

profile命令显示有关最近查询的低级信息。此命令用于诊断查询和调整性能。以下是profile命令的示例。在这种情况下， profile命令返回说明查询的低级信息。

[quickstart.cloudera:21000] > profile;

Query Runtime Profile: 
Query (id=164b1294a1049189:a67598a6699e3ab6): 

   Summary: 
      Session ID: e74927207cd752b5:65ca61e630ad3ad
      Session Type: BEESWAX 
      Start Time: 2016-04-17 23:49:26.08148000 End Time: 2016-04-17 23:49:26.2404000 
      Query Type: EXPLAIN 
      Query State: FINISHED 
      Query Status: OK 
      Impala Version: impalad version 2.3.0-cdh5.5.0 RELEASE (build 0c891d77280e2129b) 
      User: cloudera 
      Connected User: cloudera 
      Delegated User: 
      Network Address:10.0.2.15:43870 
      Default Db: my_db 
      Sql Statement: explain select * from sample 
      Coordinator: quickstart.cloudera:22000 
      : 0ns 
      Query Timeline: 167.304ms 
         - Start execution: 41.292us (41.292us) - Planning finished: 56.42ms (56.386ms) 
         - Rows available: 58.247ms (1.819ms) 
         - First row fetched: 160.72ms (101.824ms) 
         - Unregister query: 166.325ms (6.253ms)
         
   ImpalaServer: 
      - ClientFetchWaitTimer: 107.969ms 
      - RowMaterializationTimer: 0ns

表和数据库特定的选项

下表列出了Impala中的表和特定于数据的选项。

Sr.No	Command & Explanation
1	Alter The alter command is used to change the structure and name of a table in Impala.
2	Describe The describe command of Impala gives the metadata of a table. It contains the information like columns and their data types. The describe command has desc as a short cut.
3	Drop The drop command is used to remove a construct from Impala, where a construct can be a table, a view, or a database function.
4	insert The insert command of Impala is used to, Append data (columns) into a table. Override the data of an existing table. Override the data of an existing table.
5	select The select statement is used to perform a desired operation on a particular dataset. It specifies the dataset on which to complete some action. You can print or store (in a file) the result of the select statement.
6	show The show statement of Impala is used to display the metastore of various constructs such as tables, databases, and tables.
7	use The use statement of Impala is used to change the current context to the desired database.