在前面的章节中,我们已经看到使用cloudera
安装Impala及其架构.
Impala shell (命令提示符)
Hue(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的命令分为常规命令,查询特定选项和表和数据库特定选项,如下所述.
help
version
history
shell (or) !
connect
exit | quit
Set/unset
Profile
Explain
Alter
describe
drop
insert
select
show
use
打开cloudera终端,以超级用户身份登录,然后输入 cloudera 作为密码,如图所示下面.
[cloudera@quickstart ~]$ su Password: cloudera [root@quickstart cloudera]#
输入以下命令启动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的通用命令解释如下 :
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 <topic>): ======================================================== 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
version 命令为您提供当前版本的Impala,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)
Impala的 history 命令显示shell中执行的最后10个命令.以下是 history 命令的示例.这里我们执行了5个命令,即版本,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;
您可以使用退出或退出命令,如下所示.
[quickstart.cloudera:21000] > exit; Goodbye cloudera
connect command用于连接给定的Impala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的查询特定命令接受查询.它们在下面和下面解释;
explain 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
配置文件命令显示有关的低级信息最近的查询.此命令用于查询的诊断和性能调整.以下是 profile 命令的示例.在这种情况下, profile 命令返回 explain 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
下表列出了Impala中的表和数据特定选项.
Sr.No | 指挥&解释 |
---|---|
1 | alter alter 命令用于更改Impala中表格的结构和名称. |
2 | Describe Impala的 describe 命令提供表的元数据.它包含列和它们的数据类型之类的信息. describe 命令将 desc 作为捷径. |
3 | Drop drop 命令用于从Impala中删除构造,其中构造可以是表,视图或数据库函数. |
4 | insert Impala的插入命令用于,
|
5 | select select语句用于对特定数据集执行所需操作.它指定要在其上完成某些操作的数据集.您可以打印或存储(在文件中)select语句的结果. |
6 | show show 声明Impala用于显示各种结构(例如表,数据库和表)的Metastore. |
7 | use useImpala语句用于将当前上下文更改为所需数据库. |