FQL v4 will be decommissioned on June 30, 2025. Ensure that you complete your migration from FQL v4 to FQL v10 by that date.

Fauna accounts created after August 21, 2024 must use FQL v10. These accounts will not be able to run FQL v4 queries or access the v4 Dashboard.

For more details, see the v4 EOL announcement and migration guide. Contact support@fauna.com with any questions.

Intersection

This reference topic applies to FQL v4. Go to this page for the latest FQL v10 reference topics.

 
Intersection( group, ... )
intersection( group, ... )
Intersection( group, ... )
Intersection( group, ... )
Intersection( group, ... )
Intersection( group, ... )

Description

The Intersection function compares all of the items in each group, which can be an Array or Set Reference, and returns the elements that appear in every provided group.

The run time of Intersection is dependent on the size of the underlying set or page, and the exclusivity of the result. For large sets or pages with many non-exclusive items, executing Intersection might result in a query timeout error.

For query timeout errors, you may specify a larger query timeout via the driver that you are using.

Parameters

Parameter Type Definition and Requirements

group

Array or Set Reference

One or more arrays or Set References to be intersected. All provided group items must be of the same type.

Returns

When group is an Array, an array of the items that appear in every provided group.

When group is a Set Reference, a Set Reference of the items that appear in every provided group.

Examples

The following query intersects the Set Reference returned by locating the search term "fire" in the index named "spells_by_element" with the Set Reference returned by locating the search term "water" in the Index named "spells_by_element". The Paginate function executes the Set Reference and returns the results of the Intersect operation in a Page.

client.query(
  q.Paginate(
    q.Intersection(
      q.Match(q.Index('spells_by_element'), 'fire'),
      q.Match(q.Index('spells_by_element'), 'water'),
    )
  )
)
.then((ret) => console.log(ret))
.catch((err) => console.error(
  'Error: [%s] %s: %s',
  err.name,
  err.message,
  err.errors()[0].description,
))
{ data: [ Ref(Collection("spells"), "181388642071085568") ] }
result = client.query(
  q.paginate(
    q.intersection(
      q.match(q.index("spells_by_element"), "fire"),
      q.match(q.index("spells_by_element"), "water")
    )
  )
)
print(result)
{'data': [Ref(id=181388642071085568, collection=Ref(id=spells, collection=Ref(id=collections)))]}
result, err := client.Query(
	f.Paginate(
		f.Intersection(
			f.MatchTerm(f.Index("spells_by_element"), "fire"),
			f.MatchTerm(f.Index("spells_by_element"), "water"))))

if err != nil {
	fmt.Fprintln(os.Stderr, err)
} else {
	fmt.Println(result)
}
map[data:[{181388642071085568 0xc0001421e0 0xc0001421e0 <nil>}]]
try
{
    Value result = await client.Query(
        Paginate(
            Intersection(
                Match(Index("spells_by_element"), "fire"),
                Match(Index("spells_by_element"), "water")
            )
        )
    );
    Console.WriteLine(result);
}
catch (Exception e)
{
    Console.WriteLine($"ERROR: {e.Message}");
}
ObjectV(data: Arr(RefV(id = "181388642071085568", collection = RefV(id = "spells", collection = RefV(id = "collections")))))
System.out.println(
    client.query(
        Paginate(
            Intersection(
                Match(Index("spells_by_element"), Value("fire")),
                Match(Index("spells_by_element"), Value("water"))
            )
        )
    ).get());
{data: [ref(id = "181388642071085568", collection = ref(id = "spells", collection = ref(id = "collections")))]}
Paginate(
  Intersection(
    Match(Index('spells_by_element'), 'fire'),
    Match(Index('spells_by_element'), 'water'),
  )
)
{ data: [ Ref(Collection("spells"), "181388642071085568") ] }
Query metrics:

  •    bytesIn: 142

  •   bytesOut: 141

  • computeOps:   1

  •    readOps:   2

  •   writeOps:   0

  •  readBytes: 211

  • writeBytes:   0

  •  queryTime: 9ms

  •    retries:   0

The following query demonstrates how various arrays are evaluated:

client.query([
  q.Intersection(['A', 'B'], ['C', 'D']),
  q.Intersection(['A', 'B'], ['B', 'C']),
  q.Intersection(['A', 'B', 'C'], ['B', 'C'], ['B', 'C', 'D']),
  q.Intersection(['A', 'B', 'C'], ['B', 'B'], ['B']),
])
.then((ret) => console.log(ret))
.catch((err) => console.error(
  'Error: [%s] %s: %s',
  err.name,
  err.message,
  err.errors()[0].description,
))
[ [], [ 'B' ], [ 'B', 'C' ], [ 'B' ] ]
result = client.query(
  [
    q.intersection(["A", "B"], ["C", "D"]),
    q.intersection(["A", "B"], ["B", "C"]),
    q.intersection(["A", "B", "C"], ["B", "C"], ["B", "C", "D"]),
    q.intersection(["A", "B", "C"], ["B", "B"], ["B"]),
  ]
)
print(result)
[[], ['B'], ['B', 'C'], ['B']]
result, err := client.Query(
	f.Arr{
		f.Intersection(f.Arr{"A", "B"}, f.Arr{"C", "D"}),
		f.Intersection(f.Arr{"A", "B"}, f.Arr{"B", "C"}),
		f.Intersection(f.Arr{"A", "B", "C"}, f.Arr{"B", "C"}, f.Arr{"B", "C", "D"}),
		f.Intersection(f.Arr{"A", "B", "C"}, f.Arr{"B", "B"}, f.Arr{"B"}),
	})

if err != nil {
	fmt.Fprintln(os.Stderr, err)
} else {
	fmt.Println(result)
}
[[] [B] [B C] [B]]
try
{
    Value result = await client.Query(
        Arr(
            Intersection(Arr("A", "B"), Arr("C", "D")),
            Intersection(Arr("A", "B"), Arr("B", "C")),
            Intersection(Arr("A", "B", "C"), Arr("B", "C"), Arr("B", "C", "D")),
            Intersection(Arr("A", "B", "C"), Arr("B", "B"), Arr("B"))
        )
    );
    Console.WriteLine(result);
}
catch (Exception e)
{
    Console.WriteLine($"ERROR: {e.Message}");
}
Arr(Arr(), Arr(StringV(B)), Arr(StringV(B), StringV(C)), Arr(StringV(B)))
System.out.println(
    client.query(
        Arr(
            Intersection(
                Arr(Value("A"), Value("B")),
                Arr(Value("C"), Value("D"))
            ),
            Intersection(
                Arr(Value("A"), Value("B")),
                Arr(Value("B"), Value("C"))
            ),
            Intersection(
                Arr(Value("A"), Value("B"), Value("C")),
                Arr(Value("B"), Value("C")),
                Arr(Value("B"), Value("C"), Value("D"))
            ),
            Intersection(
                Arr(Value("A"), Value("B"), Value("C")),
                Arr(Value("B"), Value("B")),
                Arr(Value("B"))
            )
        )
    ).get());
[[], ["B"], ["B", "C"], ["B"]]
[
  Intersection(['A', 'B'], ['C', 'D']),
  Intersection(['A', 'B'], ['B', 'C']),
  Intersection(['A', 'B', 'C'], ['B', 'C'], ['B', 'C', 'D']),
  Intersection(['A', 'B', 'C'], ['B', 'B'], ['B'])
]
[ [], [ 'B' ], [ 'B', 'C' ], [ 'B' ] ]
Query metrics:

  •    bytesIn: 185

  •   bytesOut:  39

  • computeOps:   1

  •    readOps:   0

  •   writeOps:   0

  •  readBytes:   0

  • writeBytes:   0

  •  queryTime: 7ms

  •    retries:   0

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