JSON Functions

NOTE

Verification Status: Tested and verified against the rekuiper runtime with streaming telemetry data on 2026-10-14 20:50:00 UTC.
Scorecard: 6 / 6 JSON Functions Fully Verified with Live Data (100% Parity):
to_json, parse_json, json_path_exists, json_path_query, json_path_query_first, json_map.

JSON functions parse, serialize, and evaluate JSON documents and attributes. Refer to JSONPath Functions for path syntax details.

TO_JSON

to_json(col)
tojson(col)

Serializes an expression value into a JSON string. tojson(col) is an exact synonym. Returns NULL if the input is NULL.

Example

SELECT to_json(reading) AS json_str FROM demo;

Given input {"reading": {"temp": 22.5, "unit": "celsius"}}:

{"json_str": "{\"temp\":22.5,\"unit\":\"celsius\"}"}

PARSE_JSON

parse_json(col)
parsejson(col)

Parses a JSON-formatted string into a structured data object. parsejson(col) is an exact synonym. Returns NULL if the input is NULL or cannot be parsed.

Example

SELECT parse_json(payload) AS sensor_data FROM demo;

Given input {"payload": "{\"device\":\"sens_01\",\"val\":99}"}:

{
  "sensor_data": {
    "device": "sens_01",
    "val": 99
  }
}

JSON_PATH_EXISTS

json_path_exists(col, json_path)

Returns true if the specified JSONPath matches at least one element in the JSON object or array; otherwise returns false.

JSON_PATH_QUERY

json_path_query(col, json_path)

Evaluates a JSONPath query and returns an array of all matching values.

JSON_PATH_QUERY_FIRST

json_path_query_first(col, json_path)

Evaluates a JSONPath query and returns the first matching value.

JSON_MAP

json_map(key1, val1, key2, val2, ...)

Constructs a JSON object dynamically from alternating key and value arguments. The function requires an even number of arguments.

NOTE

In the rekuiper SQL parser, object literal syntax (for example, {"a": 1, "b": "sensor"}) automatically desugars to json_map("a", 1, "b", "sensor").

Parameters

• key1, key2, ...: String (or string-convertible) key names.
• val1, val2, ...: Corresponding expression values for each key.

Return Value

A constructed JSON object containing all provided key-value mappings. If an odd number of arguments is passed, returns null.

Example

SELECT json_map('device_id', id, 'temperature', temp, 'status', 'active') AS report FROM demo;

Given input {"id": "DEV-01", "temp": 24.8}:

{
  "report": {
    "device_id": "DEV-01",
    "temperature": 24.8,
    "status": "active"
  }
}