coll.intersection

Description

Finds the common elements between two lists, returning a new list containing only the elements that appear in both input lists.

Syntax

flex.coll.intersection(list1, list2)

Parameters

Returns

Type: list

A new list containing only the elements that exist in both input lists. Preserves the order from the first list.

Examples

Example 1: Basic Intersection

WITH [1, 2, 3, 4] AS a, [3, 4, 5, 6] AS b
RETURN flex.coll.intersection(a, b) AS result

Output:

result
-------
[3, 4]

Example 2: Finding Common Tags

MATCH (d1:Document {id: 'doc1'})
MATCH (d2:Document {id: 'doc2'})
WITH flex.coll.intersection(d1.tags, d2.tags) AS commonTags
WHERE size(commonTags) > 0
RETURN commonTags

Example 3: Finding Users with Shared Interests

MATCH (u1:User {id: $userId1})
MATCH (u2:User {id: $userId2})
WITH flex.coll.intersection(u1.interests, u2.interests) AS sharedInterests
RETURN u1.name, u2.name, sharedInterests, size(sharedInterests) AS commonCount

Example 4: Filter by Allowed Values

WITH ['admin', 'read', 'write', 'delete'] AS allowed
MATCH (u:User)
WITH u, flex.coll.intersection(u.permissions, allowed) AS validPerms
RETURN u.name, validPerms

Notes

Returns elements that exist in both lists
Preserves the order from the first list
If an element appears multiple times in list1, each occurrence is checked against list2
Efficient implementation using Set for fast lookup
Equivalent to mathematical set intersection operation