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$split

Definition

Splits text using a Java regular-expression delimiter.

Expression operator · Text · Studio Visual: available. Studio validates the complete expression separately.

Syntax

{ "$split": [ <input>, <delimiter> ] }

Replace angle-bracket placeholders with expressions or values.

Optional parameters may be omitted.

Parameters

Parameter Required Description
input Yes Expression supplying the value to process. A field reference such as "$price" reads from the current document.
delimiter Yes String separating the output parts.

Arguments are positional: keep the order shown. The authoring signature accepts 2–2 arguments.

Behavior

The following observations use the example expression below. Each row substitutes one argument while retaining the other example arguments. A missing field differs from an explicit null; the result shown is what Core actually returned.

For the input argument:

Input case Supplied value Result
null null Error — $split arguments must be strings.
missing Field absent Error — $split arguments must be strings.
decimal 2.5 Error — $split arguments must be strings.
numeric string "12" ["12"]
text "hello" ["hello"]
boolean true Error — $split arguments must be strings.
typed date {"$date":"2026-01-15T15:00:00Z"} Error — $split arguments must be strings.
empty array [] Error — $split arguments must be strings.
numeric array [1,2,3] Error — $split arguments must be strings.
object {"x":1} Error — $split arguments must be strings.

Argument handling

Invocation Result
{"$split":[]} Error — $split requires [string, delimiter]
{"$split":{"unexpected":1}} Error — $split requires [string, delimiter]

Examples

Expression: 

{
  "$split": [
    "a,b",
    ","
  ]
}

Input document: 

{}

Observed SrotaX result: ["a","b"].

Detailed input cases

Expand the complete argument-by-argument test matrix

Each table changes only the indicated argument from the example above. Other arguments retain their baseline values. Values normally come from the input field probe; literal configuration arguments are replaced directly. “Missing” means the field is absent, not explicitly null. Numeric strings are strings, not numbers.

Argument: input[0]

Input case Supplied value SrotaX result
null null Error — $split arguments must be strings.
missing Field absent Error — $split arguments must be strings.
zero 0 Error — $split arguments must be strings.
negative -2 Error — $split arguments must be strings.
decimal 2.5 Error — $split arguments must be strings.
numeric string "12" ["12"]
text "hello" ["hello"]
empty string "" [""]
boolean true Error — $split arguments must be strings.
false false Error — $split arguments must be strings.
typed date {"$date":"2026-01-15T15:00:00Z"} Error — $split arguments must be strings.
decimal128 {"$numberDecimal":"1.25"} Error — $split arguments must be strings.
empty array [] Error — $split arguments must be strings.
numeric array [1,2,3] Error — $split arguments must be strings.
mixed array [1,null,"x",3] Error — $split arguments must be strings.
nested array [[1,2],[3]] Error — $split arguments must be strings.
empty object {} Error — $split arguments must be strings.
object {"x":1} Error — $split arguments must be strings.
ISO date string "2026-01-15T15:00:00Z" ["2026-01-15T15:00:00Z"]

Argument: delimiter[1]

Input case Supplied value SrotaX result
null null Error — $split arguments must be strings.
missing Field absent Error — $split arguments must be strings.
zero 0 Error — $split arguments must be strings.
negative -2 Error — $split arguments must be strings.
decimal 2.5 Error — $split arguments must be strings.
numeric string "12" ["a,b"]
text "hello" ["a,b"]
empty string "" Error — $split delimiter must not be empty
boolean true Error — $split arguments must be strings.
false false Error — $split arguments must be strings.
typed date {"$date":"2026-01-15T15:00:00Z"} Error — $split arguments must be strings.
decimal128 {"$numberDecimal":"1.25"} Error — $split arguments must be strings.
empty array [] Error — $split arguments must be strings.
numeric array [1,2,3] Error — $split arguments must be strings.
mixed array [1,null,"x",3] Error — $split arguments must be strings.
nested array [[1,2],[3]] Error — $split arguments must be strings.
empty object {} Error — $split arguments must be strings.
object {"x":1} Error — $split arguments must be strings.
ISO date string "2026-01-15T15:00:00Z" ["a,b"]

Verification

This page records 41 executed cases. It covers individual argument substitutions, not every cross-product of arguments, locale, daylight-saving transitions, numeric overflow, collation or resource limits. No untested behavior is guaranteed.

Download exact expressions, inputs and SrotaX results. Errors are observed messages, not stable public error codes. The reference generator reads the checked-in execution report; do not edit generated observations by hand.

MongoDB differences

Compared with MongoDB 9.0.4: 8 exact BSON matches, 29 both rejected, 4 value/type/acceptance differences, 0 object-field-order differences.

“Exact” includes numeric BSON types and object key order. A value of 3 as int32 differs from 3.0 as double. Object-field-order differences are reported separately; object key ordering is not enforced by the engine regression baseline. Both rejected does not mean the error codes or messages match. This is finite-case evidence, not full compatibility certification.

Show observed differences
Tested case SrotaX MongoDB
input[0] / null Error — $split arguments must be strings. null
input[0] / missing Error — $split arguments must be strings. null
delimiter[1] / null Error — $split arguments must be strings. null
delimiter[1] / missing Error — $split arguments must be strings. null

Download full comparison evidence.