Arroyo provides two set of JSON functions, the first based on PostgreSQL’s SQL functions and syntax, and the second based on the JSONPath standard.

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SQL functions

The SQL functions provide basic JSON parsing functions similar to those found in PostgreSQL.

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json_contains

Returns true if the JSON string contains the specified key(s). 
SELECT json_contains('{"a": 1, "b": 2, "c": 3}', 'a') FROM source;
true
Also available via the ? operator: 
SELECT '{"a": 1, "b": 2, "c": 3}' ? 'a' FROM source;
true

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json_get

Retrieves the value from a JSON string by the specified path (keys). Returns the value as its native type (string, int, etc.). 
SELECT json_get('{"a": {"b": 2}}', 'a', 'b') FROM source;
2
Also available via the -> operator: 
SELECT '{"a": {"b": 2}}'->'a'->'b' FROM source;
2
Various permutations of json_get functions are available for retrieving values as a specific type, or you can use SQL type annotations: 
SELECT json_get('{"a": {"b": 2}}', 'a', 'b')::int FROM source;
2

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json_get_str

Retrieves a string value from a JSON string by the specified path. Returns an empty string if the value does not exist or is not a string. 
SELECT json_get_str('{"a": {"b": "hello"}}', 'a', 'b') FROM source;
"hello"

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json_get_int

Retrieves an integer value from a JSON string by the specified path. Returns 0 if the value does not exist or is not an integer. 
SELECT json_get_int('{"a": {"b": 42}}', 'a', 'b') FROM source;
42

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json_get_float

Retrieves a float value from a JSON string by the specified path. Returns 0.0 if the value does not exist or is not a float. 
SELECT json_get_float('{"a": {"b": 3.14}}', 'a', 'b') FROM source;
3.14

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json_get_bool

Retrieves a boolean value from a JSON string by the specified path. Returns false if the value does not exist or is not a boolean. 
SELECT json_get_bool('{"a": {"b": true}}', 'a', 'b') FROM source;
true

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json_get_json

Retrieves a nested JSON string from a JSON string by the specified path. The value is returned as raw JSON. 
SELECT json_get_json('{"a": {"b": {"c": 1}}}', 'a', 'b') FROM source;
'{"c": 1}'

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json_as_text

Retrieves any value from a JSON string by the specified path and returns it as a string, regardless of the original type. 
SELECT json_as_text('{"a": {"b": 42}}', 'a', 'b') FROM source;
"42"
Also available via the ->> operator: 
SELECT '{"a": {"b": 42}}'->>'a'->>'b' FROM source;
"42"

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json_length

Returns the length of a JSON object or array at the specified path. Returns 0 if the path does not exist or is not an object/array. 
SELECT json_length('{"a": [1, 2, 3]}', 'a') FROM source;
3

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Json path functions

JSON functions provide basic json parsing functions using JsonPath, an evolving standard for querying JSON objects.

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extract_json

Returns the JSON elements in the first argument that match the JsonPath in the second argument. The returned value is an array of json strings. 
SELECT extract_json('{"a": 1, "b": 2, "c": 3}', '$.a') FROM source;
['1']

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extract_json_string

Returns an unescaped String for the first item matching the JsonPath, if it is a string. 
SELECT extract_json_string('{"a": "a", "b": 2, "c": 3}', '$.a') FROM source;
'a'