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$switch

Definition

Selects the first branch with a true boolean condition.

Expression operator · Conditional · Studio Visual: not exposed. Studio validates the complete expression separately.

Syntax

{
  "$switch": {
    "branches": <branches>,
    "default": <default>
  }
}

Replace angle-bracket placeholders with expressions or values.

Optional parameters may be omitted.

Parameters

Parameter Required Description
branches Yes Array of objects containing case and then expressions, evaluated in order.
default No Result expression used when no branch matches. The current engine returns null when this is omitted.

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 branches argument:

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

Argument handling

Invocation Result
{"$switch":[]} Error — $switch requires a document with 'branches' and optional 'default'
{"$switch":{"unexpected":1}} Error — $switch 'branches' must be a list

Examples

Expression: 

{
  "$switch": {
    "branches": [
      {
        "case": true,
        "then": "yes"
      }
    ],
    "default": "no"
  }
}

Input document: 

{}

Observed SrotaX result: "yes".

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: branches

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

Argument: default

Input case Supplied value SrotaX result
null null "yes"
missing Field absent "yes"
zero 0 "yes"
negative -2 "yes"
decimal 2.5 "yes"
numeric string "12" "yes"
text "hello" "yes"
empty string "" "yes"
boolean true "yes"
false false "yes"
typed date {"$date":"2026-01-15T15:00:00Z"} "yes"
decimal128 {"$numberDecimal":"1.25"} "yes"
empty array [] "yes"
numeric array [1,2,3] "yes"
mixed array [1,null,"x",3] "yes"
nested array [[1,2],[3]] "yes"
empty object {} "yes"
object {"x":1} "yes"
ISO date string "2026-01-15T15:00:00Z" "yes"
omitted named argument Argument removed "yes"

Verification

This page records 43 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: 21 exact BSON matches, 22 both rejected, 0 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.

No differences were observed in the compared cases.

Download full comparison evidence.