Other Functions

NOTE

Verification Status: Tested and Verified against rekuiper engine with live telemetry stream load on 2026-10-14 20:50:00 UTC.
Scorecard: 21 Verified, 0 Unsupported, 0 Broken:

• Verified (21): isNull, coalesce, newuuid, uuid, tstamp, event_time, rule_id, rule_start, mqtt, meta, last_hit_count, last_hit_time, window_start, window_end, get_keyed_state, delay, isnan, isnumeric, nvl, cast, extract.

The following built-in functions do not belong to other function categories.

ISNULL

isNull(col)

Returns true if the argument value is null.

COALESCE

coalesce(expr1, expr2, ...)

Returns the first non-null value from the argument list. Returns null if all expressions evaluate to null.

NEWUUID

newuuid()

Returns a random 16-byte UUID string.

TSTAMP

tstamp()

Returns the current timestamp in milliseconds since 00:00:00 UTC, Thursday, 1 January 1970.

EVENT_TIME

event_time()

Returns the int64 timestamp of the event that the rule processes currently. Processing latency can cause this timestamp to be earlier than the current system time.

When you use this function as an aggregate function in a window rule, the function returns the window end time.

RULE_ID

rule_id()

Returns the identifier of the active rule.

RULE_START

rule_start()

Returns the start timestamp of the rule as an int64 integer.

MQTT

mqtt(topic)

Returns the metadata of the MQTT message. This function operates identically to meta, but you can only use it when an MQTT message triggers the rule.

META

meta(topic)

Returns the metadata of a specified key. The key format supports:

• A standalone key when the FROM clause contains only one source, such as meta(device)
• A qualified key that specifies the stream, such as meta(src1.device)
• A nested key path for multi-level metadata, such as meta(src1.reading.device.name). This format assumes that reading is a map data structure.

LAST_HIT_COUNT

last_hit_count()

Returns the number of times that the condition evaluated to true. Use this function to get the accumulated trigger count of a continuous rule. When you use this function in a WHERE clause, the function increments the count only when the condition is true.

Do not use this function in an aggregate rule, except in the WHEN clause of a sliding window. To get the hit count in an aggregate rule, use last_agg_hit_count.

When used in a sliding window trigger condition, the function updates the count when the trigger condition evaluates to true, regardless of the rule outcome.

LAST_HIT_TIME

last_hit_time()

Returns the int64 timestamp of the last event time that evaluated to true. Use this function to get the last trigger time of a continuous rule. When you use this function in a WHERE clause, the function updates the timestamp only when the condition is true.

Do not use this function in an aggregate rule, except in the WHEN clause of a sliding window. To get the hit time in an aggregate rule, use last_agg_hit_time.

When used in a sliding window trigger condition, the function updates the timestamp when the trigger condition evaluates to true, regardless of the rule outcome.

WINDOW_START

window_start()

Returns the window start timestamp as an int64 integer. Returns 0 if no time window exists. The timestamp aligns with the time configuration of the rule. If the rule uses processing time, the function returns the processing timestamp. If the rule uses event time, the function returns the event timestamp.

WINDOW_END

window_end()

Returns the window end timestamp as an int64 integer. Returns 0 if no time window exists. The timestamp aligns with the time configuration of the rule. If the rule uses processing time, the function returns the processing timestamp. If the rule uses event time, the function returns the event timestamp.

GET_KEYED_STATE

get_keyed_state(key, dataType, defaultValue)

Returns the value for the specified key from the state database. The first parameter specifies the key. The second parameter specifies the data type of the value (bigint, float, string, boolean, or datetime). The third parameter specifies the default value if the key does not exist.

The default database is SQLite. Configure an alternative database in external-state.

DELAY

delay(delayTime, returnVal)

Delays rule execution for a specified duration and then returns the value in returnVal. Specify delayTime as an integer in milliseconds.

ISNAN

isnan(col)

Returns true if the argument evaluates to an IEEE 754 NaN (Not a Number) floating-point value; otherwise returns false.

Parameters

• col: A numeric value or expression to test.

Return Value

A boolean: true if NaN, false otherwise. If col is null, returns false.

Example

SELECT isnan(temperature) AS bad_sensor FROM demo;

Given {"temperature": 25.4}:

{"bad_sensor": false}

ISNUMERIC

isnumeric(col)

Determines whether the argument is a valid numeric value or a string that can be parsed as a number.

Parameters

• col: An expression of any data type (string, integer, float, boolean, etc.).

Return Value

A boolean: true if the value is an integer, float, or a valid numeric string (e.g. '42.8', '-10'); false if non-numeric or null.

Examples

SELECT isnumeric(val_str) AS r1, isnumeric(txt) AS r2 FROM demo;

Given input {"val_str": "42.8", "txt": "hello"}:

{"r1": true, "r2": false}

NVL

nvl(expr1, expr2)

Returns the first argument if it is not null; otherwise returns the second argument as a fallback default.

Parameters

• expr1: The expression to check for null.
• expr2: The fallback replacement value if expr1 is null.

Return Value

The value of expr1 if non-null; otherwise expr2. Standard SQL NVL semantics.

Example

SELECT nvl(status_code, 200) AS code FROM demo;

Given input {"status_code": null}:

{"code": 200}

Given input {"status_code": 404}:

{"code": 404}

UUID

uuid()

Drop-in alias for newuuid(). Generates and returns a random 36-character UUID v4 string (8-4-4-4-12 hex format).

Return Value

A 36-character UUID string (for example, "3b9a1e80-87a1-4322-a9b0-9f582f3c7b21").

Example

SELECT uuid() AS message_id, temp FROM demo;

Result:

{
  "message_id": "3b9a1e80-87a1-4322-a9b0-9f582f3c7b21",
  "temp": 22.4
}

CAST

cast(col, dataType)

Converts a column or expression value to a target data type. Supported target data types include: 'bigint' (or 'int'), 'float' (or 'double'), 'string', 'boolean' (or 'bool'), 'datetime' (or 'timestamp'), and 'bytea'.

For complete type conversion rules and error handling, refer to Transformation Functions: CAST.

Example

SELECT cast(raw_reading, 'float') AS temp FROM demo;

EXTRACT

extract(map_col)

Expands a JSON object or map and flattens its key-value pairs into individual columns on the current output row in the SELECT clause.

For complete multi-row and object flattening semantics, refer to Multiple Row Functions: EXTRACT.

Example

SELECT extract(telemetry) FROM demo;