How to Fix get_json_object() Issues in Hive SQL for JSON Extraction

Discover why `get_json_object()` may fail to extract values from JSON strings in Hive SQL. Learn effective solutions for proper JSON manipulation and extraction in this comprehensive guide.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Why doesn't get_json_object() work to extract a value from JSON stored in a Hive SQL table?

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding get_json_object() in Hive SQL

If you've ever tried using get_json_object() in Hive SQL to extract a value from a JSON string, you might have encountered some challenges. This function is designed to extract data from JSON formatted strings effectively, but it comes with its quirks. One common issue users face is when the JSON structure isn't quite what they expect. In this post, we'll explore why get_json_object() might not work as intended, particularly in the context of a JSON string stored in a Hive table.

The Problem

Consider the scenario where you have a Hive table with a field containing JSON formatted strings. For example, you might have a field A that includes the following JSON:

[[See Video to Reveal this Text or Code Snippet]]

In this situation, you might try to extract the value associated with c_e_i.e_c_f using the following command:

[[See Video to Reveal this Text or Code Snippet]]

Unfortunately, if you're not getting the desired result, do not worry! You’re not alone, and we’ll address the solution in the sections below.

Why Doesn't It Work?

The primary reason get_json_object() fails in this case centers around how the JSON is formatted. Here are some key points to understand:

The value for c_e_i in your JSON string is itself a string representing another JSON object, not a JSON map.

Therefore, your structure doesn't conform to what get_json_object() expects for deeper nested extraction. Instead of a proper nested map, you have a single-level map where the value is a string rather than an object.

To clarify, it should look like this to work correctly:

[[See Video to Reveal this Text or Code Snippet]]

In this structure, c_e_i directly contains another JSON object—making it possible to navigate deeper into the JSON structure.

Solutions to Extract JSON Values

Now that we understand the problem, let’s look at a few methods you can employ to successfully extract the value.

Method 1: Dual Extraction Approach

To handle the string value correctly, you can apply get_json_object() twice. First, extract c_e_i, then extract e_c_f from the resulting JSON. Here’s how:

[[See Video to Reveal this Text or Code Snippet]]

Result:

You can expect a result akin to:

[[See Video to Reveal this Text or Code Snippet]]

This approach successfully navigates through the nested strings to yield the desired value.

Method 2: Transforming the JSON Structure

If you prefer to manipulate and correct the JSON string structurally, you can use the regexp_replace function to sanitize the original string before extracting:

[[See Video to Reveal this Text or Code Snippet]]

Result:

Here’s what it would produce:

[[See Video to Reveal this Text or Code Snippet]]

This method reshapes the JSON, making it easier for get_json_object() to pull the required values without additional complexity.

Conclusion

Whether you choose to extract values step-by-step or transform your JSON format, understanding the intricacies of JSON in Hive SQL allows you to overcome common challenges effectively. Leveraging the get_json_object() function correctly can save you time and improve your data processing workflows.

By following the outlined methods, you'll be better prepared to tackle similar JSON extraction issues in your own projects. Happy querying!