map.submap

Description

Creates a new map containing only the specified keys from the input map. This is the inverse of removeKeys.

Syntax 

flex.map.submap(map, keys)

Parameters

| Parameter | Type | Required | Description | |———–|——|———-|————-| | map | map | Yes | The source map to extract keys from | | keys | list | Yes | An array of key names to include in the result |

Returns

Type: map (object)

A new map containing only the specified keys and their values from the input map. Returns an empty map if input is not a valid object or keys is not an array.

Examples

Example 1: Basic Submap Extraction 

WITH {name: 'Alice', age: 30, email: 'alice@example.com', city: 'NYC'} AS user
RETURN flex.map.submap(user, ['name', 'email']) AS contact

Output:

contact
---------------------------------
{name: 'Alice', email: 'alice@example.com'}

Example 2: Selecting Specific Node Properties 

MATCH (p:Product)
RETURN flex.map.submap(properties(p), ['id', 'name', 'price']) AS summary

Example 3: Building API Response with Selected Fields 

MATCH (u:User {id: $userId})
WITH properties(u) AS allProps
RETURN flex.map.submap(allProps, ['id', 'name', 'email', 'role']) AS userInfo

Example 4: Handling Non-Existent Keys 

WITH {a: 1, b: 2} AS map
RETURN flex.map.submap(map, ['a', 'c', 'd']) AS result

Output:

result
------
{a: 1}

(Only existing keys are included)

Example 5: Dynamic Field Selection 

WITH ['name', 'price', 'category'] AS requestedFields
MATCH (p:Product {id: 123})
RETURN flex.map.submap(properties(p), requestedFields) AS response

Notes

  • Returns empty map if input is not a valid object or keys is not an array
  • null values in the keys array are ignored
  • Non-existent keys are silently skipped
  • Creates a new map; does not modify the original
  • Useful for selecting specific fields, building API responses, or data projection
  • More efficient than manually picking each field

See Also