Apache Hive provides several inbuilt functions to process the data. One of these is the hash() function, which calculates a signed 64-bit hash value over a set of input rows. This function becomes useful when you want to compare rows for equality, for instance. Here’s a step-by-step guide on how to utilize this function.
Step 1: Data Definition
First, we need to create a table where we will insert our data. In this example, we’ll create a simple table called user_data that consists of three columns, user_id, user_name, and user_country. The Data Definition Language (DDL) statement is as follows:
CREATE TABLE user_data (
user_id INT,
user_name STRING,
user_country STRING
);
Step 2: Inserting Data
Once we’ve created the table, we’ll insert some data into it:
INSERT INTO TABLE user_data (user_id, user_name, user_country) VALUES (1, 'Sachin P', 'USA');
INSERT INTO TABLE user_data (user_id, user_name, user_country) VALUES (2, 'Rajesh K', 'UK');
INSERT INTO TABLE user_data (user_id, user_name, user_country) VALUES (3, 'Karthik', 'INDIA');
INSERT INTO TABLE user_data (user_id, user_name, user_country) VALUES (4, 'Suresh', 'SINGAPORE');
Step 3: Utilizing the Hash Function
Now that we have some data, let’s utilize the hash() function. We can generate a 64-bit signed hash value for each row in our table. This hash value will be calculated based on all columns in the row:
SELECT user_id, user_name, user_country, hash(user_id, user_name, user_country) as hash_value
FROM user_data;
This will return each row in the user_data table along with a 64-bit signed hash value, calculated based on all columns (user_id, user_name, user_country) in the row.
Please execute all the above queries in Hive Shell or any other interface that you use to interact with Hive. Make sure that your Hive Server is running before executing these commands.
Remember, the hash() function in Hive does not guarantee the uniqueness of the hash value, meaning different inputs could potentially result in the same hash value (although the likelihood is low).
And that’s it! Now you have a basic understanding of how to use the hash() function in Apache Hive to generate 64-bit hash values.
The result of the SELECT statement that includes the hash() function will be dependent on the actual data and the hash function’s internal implementation, which can vary. However, the output structure will look something like this:
user_id user_name user_country hash_value
1 Sachin P USA -8989897845994144242
2 Rajesh J UK -5817585452123663142
3 Karthik INDIA -7512545875455571279
4 Suresh INDIA -3732565452587472178
Hive important pages to refer
