Apache Tajo JSON Functions

Apache Tajo is a big data relational and distributed data warehouse system that runs on top of Hadoop. It provides various functions for processing large-scale data efficiently. One of the most useful functions is the JSON functions that allow developers to work with JSON data.

Supported JSON Functions in Tajo

• json_extract_path(json, path): This function extracts a value from a JSON object using a JSON path expression. For example, SELECT json_extract_path('{"name": "John", "age": 30}', 'name') returns John.

• json_extract_array_element(json, index): This function extracts an element from a JSON array at a specified index. For example, SELECT json_extract_array_element('["John", "Doe", "Mary"]', 2) returns Mary.

• json_type(json): This function returns the type of a JSON value. For example, SELECT json_type('{"name": "John", "age": 30}') returns object.

• json_array_length(json): This function returns the length of a JSON array. For example, SELECT json_array_length('["John", "Doe", "Mary"]') returns 3.

Examples

Here are some examples of using Apache Tajo JSON functions:

• Extracting values from a JSON object:

SELECT json_extract_path('{"name": "John", "age": 30}', 'name') as name, 
       json_extract_path('{"name": "John", "age": 30}', 'age') as age;

Output:

|name|age| |----|---| |John|30 |

• Extracting elements from a JSON array:

SELECT json_extract_array_element('["John", "Doe", "Mary"]', 2) as name;

Output:

|name| |----| |Mary|

• Getting the type of a JSON value:

SELECT json_type('{"name": "John", "age": 30}') as type;

Output:

|type| |----| |object|

• Getting the length of a JSON array:

SELECT json_array_length('["John", "Doe", "Mary"]') as length;

Output:

|length| |------| | 3 |

In conclusion, Apache Tajo JSON functions make it easy for programmers to work with JSON data in a distributed environment. The functions are efficient and support a wide range of use cases.