配置单元中的映射类型变量 [英] Map type variable in hive

问题描述

我试图在配置单元中定义地图类型时遇到问题。根据 Hive手册，肯定有地图类型，不幸的是没有任何关于如何使用它的例子。 :-(

I am having trouble trying to define map type in hive. According to Hive Manual there definitely is a map type, unfortunately there aren't any examples on how to use it. :-(

假设，我有一个包含以下列的表（用户）：

Suppose, I have a table (users) with following columns:

Name     Ph    CategoryName

这个CategoryName列有一组特定的值。希望创建一个将CategoryName映射到CategoryID的散列表，我尝试过：

This "CategoryName" column has specific set of values. Now I want to create a hashtable that maps CategoryName to CategoryID. I tried doing:

set hivevar:nameToID=map('A',1,'B',2); 

我有两个问题：

I have 2 questions:

1. 当我做设置hivevar：$ {nameToID ['A']} 我认为它将打印出价值为1.但我得到
   $ {hivevar：nameToID ['A']}未定义

1. When I do set hivevar:${nameToID['A']} I thought that it would print out value as 1. But I get "${hivevar:nameToID['A']} is undefined"

我不是确定我怎么能说，像 select name，ph，$ {nameToID [CategoryName]}这样的用户

I am not sure how can I say something like, select name, ph, ${nameToID[CategoryName]} from users

请让我知道这些
Thanks！

Please let me know about these. Thanks!

推荐答案

假设您有以下表格：

Let's assume you have the following table:

describe test;
name      string    
ph        string    
category  map<string,int>

select * from test;
name    ph  category
Name1   ph1 {"type":1000,"color":200,"shape":610}
Name2   ph2 {"type":2000,"color":200,"shape":150}
Name3   ph3 {"type":3000,"color":700,"shape":167}

访问地图列：

Accessing the map column :

select ph, category["type"], category["color"] from test;
ph1    1000    200
ph2    2000    200
ph3    3000    700

使用Hive变量的等价物：

An equivalent using a Hive variable:

set hivevar:nameToID=
   map("t", category["type"], "c", category["color"], "s", category["shape"]);

select ph, ${nameToID}["t"], ${nameToID}["c"] from test;
ph1    1000    200
ph2    2000    200
ph3    3000    700

这适用于Hive 0.9.0

This works on Hive 0.9.0

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