Hive : How to update the access time of a file or directory in the Hive data warehouse [Touch]

Among the many functions Hive provides, one essential operation is “TOUCH.” In this article, we will explore the purpose of the “TOUCH” command in Hive, its main use cases, and provide a real-world example to demonstrate its practical application.

What is the “TOUCH” command in Hive?

The “TOUCH” command in Hive is used to update the access time of a file or directory in the Hive data warehouse. Hive, by default, tracks access times for tables and partitions, which means each time a table or partition is accessed, the access timestamp is updated. However, when dealing with external tables, this automatic update of access times may not occur. This is where the “TOUCH” command comes into play.

Main Use of “TOUCH” in Hive:

1. Updating Access Time: The primary use of the “TOUCH” command is to update the access time of external tables or partitions manually. By doing so, you can ensure that the access times are correctly recorded for these external data sources, which can be crucial for various data management and analysis tasks.

When to use the “TOUCH” command in Hive?

The “TOUCH” command should be used in scenarios where you have external tables or partitions in Hive and you want to update their access times manually. It is especially useful in situations where the default automatic access time update is disabled or not functioning correctly. Additionally, when you want to maintain better control over the access timestamps for specific datasets, using “TOUCH” becomes essential.

Real-World Example:

Let’s consider a real-world example where the “TOUCH” command in Hive can be utilized.

Suppose you have an external table named “website_logs” in Hive, which contains web server logs from various websites. The logs are stored in an external directory named “/user/hive/external_logs“.

Initially, the access time for the “website_logs” table is not getting updated automatically, and you want to ensure that the access time is recorded correctly for auditing purposes. To achieve this, you can use the “TOUCH” command as follows:

-- Update the access time of the entire table
TOUCH TABLE website_logs;

-- Update the access time for a specific partition (if the table is partitioned)
TOUCH TABLE freshers_in_logs PARTITION(dt='2023-08-01');