Map Type Variable in Hive
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...
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. :-(
Suppose, I have a table (users) with following columns:
Name Ph CategoryName
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);
I have 2 questions:
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"I am not sure how can I say something like,
select name, ph, ${nameToID[CategoryName]} from users
1 Answer
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}
Accessing the map column :
select ph, category["type"], category["color"] from test;
ph1 1000 200
ph2 2000 200
ph3 3000 700
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
This works on Hive 0.9.0
Maya is a hardware enthusiast who tests and reviews smart home devices, smartphones, wearables, and audio gear. She focuses on practical consumer value and build quality.
