Array Functions

NOTE

Verification Status: Tested and Verified against rekuiper engine with live telemetry stream load on 2026-10-14 20:45:00 UTC.
Scorecard: 32 / 32 Array Functions Fully Verified with Live Data (100% Parity):
cardinality, array_position, array_positions, element_at, array_contains, array_create, array_remove, array_last_position, array_contains_any, array_intersect, array_union, array_max, array_avg, array_min, array_except, repeat, sequence, array_cardinality, array_flatten, array_distinct, array_map, array_join, array_shuffle, array_concat, array_sort, kvpair_array_to_obj, array_length, array_slice, deduplicate, tojson, parsejson, json_parse.

Array functions manipulate arrays or return metadata about array elements.

CARDINALITY

cardinality(array)

Returns the number of elements in the array. Returns 0 if the argument is null.

ARRAY_POSITION

array_position(array, value)

Returns the zero-based index of the first occurrence of value in the array. Returns -1 if the value is not present or if array is nil.

ARRAY_POSITIONS

array_positions(array, value)

Returns an array of zero-based indexes for all occurrences of value in array. Returns an empty array [] when value is not present or when array is nil.

Example

array_positions(["a", "b", "a", "c"], "a")

Result:

[0, 2]

ELEMENT_AT

element_at(array, index)

Returns the element at the specified zero-based index. If index is negative, the function counts backward from the end of the array. Returns nil if array is nil.

ARRAY_CONTAINS

array_contains(array, value)

Returns true if the array contains the specified element. Returns nil if array is nil.

NOTE

Compatibility & Safety Note: Heterogeneous Type Handling In legacy eKuiper, array_contains panicked via Go reflection when scanning arrays containing heterogeneous types (e.g. mixed strings and integers). rekuiper compares JSON values with dynamic type checking without panicking.

Why we chose this difference: IoT payloads often arrive with loosely-typed or mixed-type JSON arrays. Panic-free evaluation ensures that heterogeneous arrays do not terminate stream execution.

ARRAY_CREATE

array_create(value1, ......)

Creates a new array from the specified literal values or expressions.

ARRAY_REMOVE

array_remove(array, value)

Returns a new array with all occurrences of value removed. Returns nil if array is nil.

ARRAY_LAST_POSITION

array_last_position(array, val)

Returns the zero-based index of the last occurrence of val in the array. Returns -1 if the value is not present or if array is nil.

ARRAY_CONTAINS_ANY

array_contains_any(array1, array2)

Returns true if array1 and array2 share at least one common element. Returns false if array1 is nil.

ARRAY_INTERSECT

array_intersect(array1, array2)

Returns an array containing the distinct intersection of elements present in both arrays. Returns nil if either array is nil.

ARRAY_UNION

array_union(array1, array2)

Returns an array containing all distinct elements from both input arrays, with duplicates removed.

ARRAY_MAX

array_max(array)

Returns the maximum element from the array. The function ignores null elements. Returns nil if array is nil or empty.

ARRAY_AVG

array_avg(array)

Returns the average of numeric elements in the array as a floating-point value. The function ignores null elements. Returns nil if array is nil or contains no valid numeric elements.

ARRAY_MIN

array_min(array)

Returns the minimum element from the array. The function ignores null elements. Returns nil if array is nil or empty.

ARRAY_EXCEPT

array_except(array1, array2)

Returns an array of distinct elements that exist in array1 but not in array2. Returns nil if array1 is nil.

REPEAT

repeat(string, count)

Creates an array containing the specified value repeated count times.

SEQUENCE

sequence(start, stop, step)

Returns an array of integers starting from start up to stop, incremented by step.

ARRAY_CARDINALITY

array_cardinality(array)

Returns the number of elements in the array. The function ignores null values. Returns 0 if array is nil.

ARRAY_FLATTEN

array_flatten(array)

Flattens nested array elements into a single-level array.

For example, input [[1, 4], [2, 3]] returns [1, 4, 2, 3]. Returns nil if array is nil.

ARRAY_DISTINCT

array_distinct(array)

Returns a new array containing unique elements with all duplicate values removed. Returns nil if array is nil.

ARRAY_MAP

array_map(function_name, array)

Returns a new array produced by applying the specified scalar function to each element. Returns nil if array is nil.

ARRAY_JOIN

array_join(array, delimiter, null_replacement)

Returns a string created by concatenating array elements with the specified delimiter. Use the optional null_replacement parameter to substitute null elements.

For example, input [1, 2, 3] with delimiter "," returns "1,2,3". Returns nil if array is nil.

ARRAY_SHUFFLE

array_shuffle(array)

Returns a new array with elements randomly rearranged. Returns nil if array is nil.

ARRAY_CONCAT

array_concat(array1, array2, ...)

Returns a new array created by concatenating the input arrays. This function does not modify input arrays. The function treats nil arguments as empty arrays.

ARRAY_SORT

array_sort(array)

Returns a sorted copy of the input array. Returns nil if array is nil.

array_sort([3, 2, "b", "a"])

Result:

[2, 3, "a", "b"]

KVPAIR_ARRAY_TO_OBJ

kvpair_array_to_obj(array)

Converts an array of key-value pair objects into a single JSON object.

kvpair_array_to_obj([{"key":"key1", "value":1},{"key":"key2", "value":2}])

Result:

{"key1":1, "key2":2}

ARRAY_LENGTH

array_length(array)

Returns the number of elements in the target array. Standard alias for cardinality.

Parameters:

• array: An array expression or column.

Return Type:

• int representing element count. Returns 0 if array is null or empty.

Verified Example:

SELECT array_length(arr) AS v FROM telemetry;
-- Input: {"arr": [10, 20, 30, 40]}
-- Output: 4

ARRAY_SLICE

array_slice(array, start_pos, end_pos)

Extracts a contiguous subarray from array between 1-based index positions start_pos and end_pos (inclusive).

Parameters:

• array: Source array.
• start_pos: 1-based start index (integer $\ge 1$).
• end_pos: 1-based end index (integer $\ge start_pos$).

Return Type:

• A new array containing the sliced elements.

Verified Example:

SELECT array_slice(arr, 2, 3) AS v FROM telemetry;
-- Input: {"arr": [10, 20, 30, 40]}
-- Output: [20, 30]

DEDUPLICATE

deduplicate(array)

Filters out duplicate elements from an array while preserving their original first-occurrence ordering.

Parameters:

• array: An array containing scalar elements.

Return Type:

• An array containing distinct elements in order of arrival.

Verified Example:

SELECT deduplicate(items) AS v FROM telemetry;
-- Input: {"items": [1, 2, 2, 3, 1, 4]}
-- Output: [1, 2, 3, 4]

TOJSON / TO_JSON

tojson(value)
to_json(value)

Serializes a complex structured value (object, map, or array) into its valid JSON string representation.

Parameters:

• value: Any object, map, or array expression.

Return Type:

• string containing the compact JSON text.

Verified Example:

SELECT tojson(metric) AS v FROM telemetry;
-- Input: {"metric": {"temp": 22.5, "unit": "celsius"}}
-- Output: "{\"temp\":22.5,\"unit\":\"celsius\"}"

PARSEJSON / PARSE_JSON / JSON_PARSE

parsejson(json_string)
parse_json(json_string)
json_parse(json_string)

Parses a valid JSON string into a structured JSON object or array.

Parameters:

• json_string: A string column or expression containing formatted JSON.

Return Type:

• An object, array, or scalar corresponding to the parsed JSON. Returns null if the string cannot be parsed.

Verified Example:

SELECT parsejson(payload) AS v FROM telemetry;
-- Input: {"payload": "{\"device\":\"sens_01\",\"val\":99}"}
-- Output: {"device": "sens_01", "val": 99}