May 26, 2021 impala
In the previous sections, we've seen installing Impala using cloudera and its architecture.
This chapter describes how to launch the various options for Impala Shell and Shell.
Impala shell's commands are divided into general commands that query specific options, as well as table and database-specific options, as described below.
Open the cloudera terminal, log in as a super user, and type cloudera as your password, as shown below.
[cloudera@quickstart ~]$ su Password: cloudera [root@quickstart cloudera]#
Start Impala shell by typing the following command -
[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's general command is explained below -
Impala shell's help command provides a list of commands available in Impala -
[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
The version command gives you the current version of Impala, as shown below.
[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's highstory command shows the last 10 commands executed in the shell. T he following is an example of a historical command. H ere we execute 5 commands, namely version, help, display, usage, and history.
[quickstart.cloudera:21000] > history; [1]:version; [2]:help; [3]:show databases; [4]:use my_db; [5]:history;
You can use the quit or exit command to eject from the Impala shell, as shown below.
[quickstart.cloudera:21000] > exit; Goodbye cloudera
The connect command is used to connect to a given instance of Impala. If no instance is specified, it will connect to the default port 21000, as shown below.
[quickstart.cloudera:21000] > connect; Connected to quickstart.cloudera:21000 Server version: impalad version 2.3.0-cdh5.5.0 RELEASE (build 0c891d79aa38f297d244855a32f1e17280e2129b)
Impala's query-specific command accepts queries. T hey explain below -
The explain command returns the execution plan for a given query.
[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
The profile command displays low-level information about the most recent query. T his command is used to query diagnostics and performance adjustments. T he following is an example of a profile command. In this case, the profile command returns low-level information that describes the query.
[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
The following table lists table and data-specific options in Impala.
| Sr.No | commanding explanation |
|---|---|
| 1 |
Alter The alter command is used to change the structure and name of the table in Impala. |
| 2 |
Describe Impala's describe command provides the table's metadata. I t contains information such as columns and their data types. T he describe command has desc as a shortcut. |
| 3 |
Drop Drop commands are used to remove constructs from Impala, where the constructs can be tables, views, or database functions. |
| 4 |
insert Impala's insert command is used
|
| 5 |
select Select statements are used to perform the required actions on a particular dataset. I t specifies the dataset on which to complete certain operations. Y ou can print or store the results of select statements (in a file). |
| 6 |
show Impala's show statements are used to display relays for various constructs, such as tables, databases, and tables. |
| 7 |
use Impala's use statement is used to change the current context to the desired database. |