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