Hcatalog 简明教程

HCatalog - CLI

HCatalog 命令行界面 (CLI) 可以从命令 $HIVE_HOME/HCatalog/bin/hcat 中调用，其中 $HIVE_HOME 是 Hive 的主目录。 hcat 是用于初始化 HCatalog 服务器的命令。

HCatalog Command Line Interface (CLI) can be invoked from the command $HIVE_HOME/HCatalog/bin/hcat where $HIVE_HOME is the home directory of Hive. hcat is a command used to initialize the HCatalog server.

使用以下命令初始化 HCatalog 命令行。

Use the following command to initialize HCatalog command line.

cd $HCAT_HOME/bin
./hcat

如果安装已正确完成，则您将获得以下输出 −

If the installation has been done correctly, then you will get the following output −

SLF4J: Actual binding is of type [org.slf4j.impl.Log4jLoggerFactory]
usage: hcat { -e "<query>" | -f "<filepath>" }
   [ -g "<group>" ] [ -p "<perms>" ]
   [ -D"<name> = <value>" ]

-D <property = value>    use hadoop value for given property
-e <exec>                hcat command given from command line
-f <file>                hcat commands in file
-g <group>               group for the db/table specified in CREATE statement
-h,--help                Print help information
-p <perms>               permissions for the db/table specified in CREATE statement

HCatalog CLI 支持这些命令行选项 −

The HCatalog CLI supports these command line options −

Sr.No

Option

Example & Description

1

-g

hcat -g mygroup …​ The table to be created must have the group "mygroup".

2

-p

hcat -p rwxr-xr-x …​ The table to be created must have read, write, and execute permissions.

3

-f

hcat -f myscript.HCatalog …​ myscript.HCatalog is a script file containing DDL commands to execute.

4

-e

hcat -e 'create table mytable(a int);' …​ Treat the following string as a DDL command and execute it.

5

-D

hcat -Dkey = value …​ Passes the key-value pair to HCatalog as a Java system property.

6

-

hcat Prints a usage message.

Note −

  1. The -g and -p options are not mandatory.

  2. At one time, either -e or -f option can be provided, not both.

  3. The order of options is immaterial; you can specify the options in any order.

Sr.No

DDL Command & Description

1

CREATE TABLE Create a table using HCatalog. If you create a table with a CLUSTERED BY clause, you will not be able to write to it with Pig or MapReduce.

2

ALTER TABLE Supported except for the REBUILD and CONCATENATE options. Its behavior remains same as in Hive.

3

DROP TABLE Supported. Behavior the same as Hive (Drop the complete table and structure).

4

CREATE/ALTER/DROP VIEW Supported. Behavior same as Hive. Note − Pig and MapReduce cannot read from or write to views.

5

SHOW TABLES Display a list of tables.

6

SHOW PARTITIONS Display a list of partitions.

7

Create/Drop Index CREATE and DROP FUNCTION operations are supported, but the created functions must still be registered in Pig and placed in CLASSPATH for MapReduce.

8

DESCRIBE Supported. Behavior same as Hive. Describe the structure.

上表中的一些命令在后续章节中进行了说明。

Some of the commands from the above table are explained in subsequent chapters.