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.

`IsSet`

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

IsSet( value )

is_set( value )

IsSet( value )

IsSet( value )

IsSet( value )

IsSet( value )

Description

The IsSet function returns true only if value is a Set, otherwise it returns false.

Parameters

Parameter Type Definition and Requirements

Parameter	Type	Definition and Requirements
`value`	Any	Any value, which is to be tested to determine whether it is a Set or not.

value

Any

Any value, which is to be tested to determine whether it is a Set or not.

Returns

Returns a boolean, indicating whether value was a set or not.

Examples

The following query uses Map to iterate over an array of all of the types of values that can be tested by a type-check function, passing each item into a Lambda function that returns an object, which contains the value and the result of calling IsSet with that value:

client.query(
  q.Map(
    [
      ['array'],
      true,
      false,
      new Uint8Array([1, 2, 3, 4]),
      [0x1, 0x2, 0x3, 0x4],
      q.Collection('Letters'),
      q.Ref('credentials/self'),
      q.Database('child_db'),
      q.Date('2019-11-12'),
      q.Ref(q.Collection('Letters'), 123),
      10.1,
      q.Function('double'),
      q.Index('letters'),
      10,
      q.Ref(q.Keys(), '1'),
      q.Query(q.Lambda('x', q.Var('x'))),
      null,
      { x: 10 },
      q.Role('employees'),
      q.Match(q.Index('letters')),
      'ten',
      '10',
      q.Time('2020-07-06T12:34:56.789Z'),
      q.Ref(q.Tokens(), '1'),
    ],
    q.Lambda('x', {
      value: q.Var('x'),
      IsSet: q.IsSet(q.Var('x')),
    })
  )
)
.then((ret) => console.log(ret))
.catch((err) => console.error(
  'Error: [%s] %s: %s',
  err.name,
  err.message,
  err.errors()[0].description,
))

[
  { value: [ 'array' ], IsSet: false },
  { value: true, IsSet: false },
  { value: false, IsSet: false },
  { value: Bytes("AQIDBA=="), IsSet: false },
  { value: [ 1, 2, 3, 4 ], IsSet: false },
  { value: Collection("Letters"), IsSet: false },
  { value: Ref(Credentials(), "268435422873387520"), IsSet: false },
  { value: Database("child_db"), IsSet: false },
  { value: Date("2019-11-12"), IsSet: false },
  { value: Ref(Collection("Letters"), "123"), IsSet: false },
  { value: 10.1, IsSet: false },
  { value: Function("double"), IsSet: false },
  { value: Index("letters"), IsSet: false },
  { value: 10, IsSet: false },
  { value: Ref(Keys(), "1"), IsSet: false },
  { value: Query(Lambda("x", Var("x"))), IsSet: false },
  { value: null, IsSet: false },
  { value: { x: 10 }, IsSet: false },
  { value: Role("employees"), IsSet: false },
  { value: Match(Index("letters")), IsSet: true },
  { value: 'ten', IsSet: false },
  { value: '10', IsSet: false },
  { value: Time("2020-06-15T22:06:59.634Z"), IsSet: false },
  { value: Ref(Tokens(), "1"), IsSet: false }
]

result = client.query(
  q.map_(
    q.lambda_("x", {
      "value": q.var("x"),
      "IsSet": q.is_set(q.var("x")),
    }),
    [
      ["array"],
      True,
      False,
      bytearray([1, 2, 3, 4]),
      [0x1, 0x2, 0x3, 0x4],
      q.collection("Letters"),
      q.ref("credentials/self"),
      q.database("child_db"),
      q.date("2019-11-12"),
      q.ref(q.collection("Letters"), 123),
      10.1,
      q.function("double"),
      q.index("letters"),
      10,
      q.ref(q.keys(), "1"),
      q.query(q.lambda_("x", q.var("x"))),
      None,
      {"x": 10},
      q.role("employees"),
      q.match(q.index("letters")),
      "ten",
      "10",
      q.time("2020-07-06T12:34:56.789Z"),
      q.ref(q.tokens(), "1"),
    ],
  )
)
print(result)

[{'value': ['array'], 'IsSet': False}, {'value': True, 'IsSet': False}, {'value': False, 'IsSet': False}, {'value': bytearray(b'\x01\x02\x03\x04'), 'IsSet': False}, {'value': [1, 2, 3, 4], 'IsSet': False}, {'value': Ref(id=Letters, collection=Ref(id=collections)), 'IsSet': False}, {'value': Ref(id=282032258185953792, collection=Ref(id=credentials)), 'IsSet': False}, {'value': Ref(id=child_db, collection=Ref(id=databases)), 'IsSet': False}, {'value': datetime.date(2019, 11, 12), 'IsSet': False}, {'value': Ref(id=123, collection=Ref(id=Letters, collection=Ref(id=collections))), 'IsSet': False}, {'value': 10.1, 'IsSet': False}, {'value': Ref(id=double, collection=Ref(id=functions)), 'IsSet': False}, {'value': Ref(id=letters, collection=Ref(id=indexes)), 'IsSet': False}, {'value': 10, 'IsSet': False}, {'value': Ref(id=1, collection=Ref(id=keys)), 'IsSet': False}, {'value': Query({'api_version': '4', 'lambda': 'x', 'expr': {'var': 'x'}}), 'IsSet': False}, {'value': None, 'IsSet': False}, {'value': {'x': 10}, 'IsSet': False}, {'value': Ref(id=employees, collection=Ref(id=roles)), 'IsSet': False}, {'value': SetRef({'match': Ref(id=letters, collection=Ref(id=indexes))}), 'IsSet': True}, {'value': 'ten', 'IsSet': False}, {'value': '10', 'IsSet': False}, {'value': FaunaTime('2020-07-06T12:34:56.789Z'), 'IsSet': False}, {'value': Ref(id=1, collection=Ref(id=tokens)), 'IsSet': False}]

result, err := client.Query(
	f.Map(
		f.Arr{
			f.Arr{"array"},
			true,
			false,
			f.BytesV{0x01, 0x02, 0x03, 0x04},
			f.Arr{0x1, 0x2, 0x3, 0x4},
			f.Collection("Letters"),
			f.Ref("credentials/self"),
			f.Database("child_db"),
			f.Date("2019-11-12"),
			f.Ref(f.Collection("Letters"), 123),
			10.1,
			f.Function("double"),
			f.Index("letters"),
			10,
			f.Ref(f.Keys(), "1"),
			f.Query(f.Lambda("x", f.Var("x"))),
			nil,
			f.Null(),
			f.Obj{"x": 10},
			f.Role("employees"),
			f.Match(f.Index("letters")),
			"ten",
			"10",
			f.Time("2020-07-06T12:34:56.789Z"),
			f.Ref(f.Tokens(), "1"),
		},
		f.Lambda("x", f.Obj{
			"value": f.Var("x"),
			"IsSet": f.IsSet(f.Var("x")),
		})))

if err != nil {
	fmt.Fprintln(os.Stderr, err)
} else {
	fmt.Println(result)
}

[map[IsSet:false value:[array]] map[IsSet:false value:true] map[IsSet:false value:false] map[IsSet:false value:[1 2 3 4]] map[IsSet:false value:[1 2 3 4]] map[IsSet:false value:{Letters 0xc00009a240 0xc00009a240 <nil>}] map[IsSet:false value:{280481857410171392 0xc00009a360 0xc00009a360 <nil>}] map[IsSet:false value:{child_db 0xc00009a480 0xc00009a480 <nil>}] map[IsSet:false value:{0 63709113600 <nil>}] map[IsSet:false value:{123 0xc0000bfd70 0xc0000bfd70 <nil>}] map[IsSet:false value:10.1] map[IsSet:false value:{double 0xc0000bfec0 0xc0000bfec0 <nil>}] map[IsSet:false value:{letters 0xc00018c000 0xc00018c000 <nil>}] map[IsSet:false value:10] map[IsSet:false value:{1 0xc00018c150 0xc00018c150 <nil>}] map[IsSet:false value:{[123 34 97 112 105 95 118 101 114 115 105 111 110 34 58 34 51 34 44 34 108 97 109 98 100 97 34 58 34 120 34 44 34 101 120 112 114 34 58 123 34 118 97 114 34 58 34 120 34 125 125]}] map[IsSet:false value:{}] map[IsSet:false value:{}] map[IsSet:false value:map[x:10]] map[IsSet:false value:{employees 0xc00018c360 0xc00018c360 <nil>}] map[IsSet:true value:{map[match:{letters 0xc00018c4b0 0xc00018c4b0 <nil>}]}] map[IsSet:false value:ten] map[IsSet:false value:10] map[IsSet:false value:{789000000 63729635696 <nil>}] map[IsSet:false value:{1 0xc00018c660 0xc00018c660 <nil>}]]

try
{
    Value result = await client.Query(
        Map(
            Arr(
                Arr("array"),
                true,
                false,
                BytesV.Of(0x1, 0x2, 0x3, 0x4),
                Arr(0x1, 0x2, 0x3, 0x4),
                Collection("Letters"),
                Ref("credentials/self"),
                Database("child_db"),
                Date("2019-11-12"),
                Ref(Collection("Letters"), 123),
                10.1,
                Function("double"),
                Index("letters"),
                10,
                Ref(Keys(), "1"),
                Query(Lambda("x", Var("x"))),
                null,
                Obj("x", 10),
                Role("employees"),
                Match(Index("letters")),
                "ten",
                "10",
                Time("2020-07-06T12:34:56.789Z"),
                Ref(Tokens(), "1")
            ),
            Lambda(
                "x",
                Obj(
                    "value", Var("x"),
                    "IsSet", IsSet(Var("x"))
                )
            )
        )
    );

    Console.WriteLine(result);
}
catch (Exception e)
{
    Console.WriteLine($"ERROR: {e.Message}");
}

Arr(ObjectV(value: Arr(StringV(array)),IsSet: BooleanV(False)), ObjectV(value: BooleanV(True),IsSet: BooleanV(False)), ObjectV(value: BooleanV(False),IsSet: BooleanV(False)), ObjectV(value: BytesV(0x01, 0x02, 0x03, 0x04),IsSet: BooleanV(False)), ObjectV(value: Arr(LongV(1), LongV(2), LongV(3), LongV(4)),IsSet: BooleanV(False)), ObjectV(value: RefV(id = "Letters", collection = RefV(id = "collections")),IsSet: BooleanV(False)), ObjectV(value: RefV(id = "295432337955488256", collection = RefV(id = "credentials")),IsSet: BooleanV(False)), ObjectV(value: RefV(id = "child_db", collection = RefV(id = "databases")),IsSet: BooleanV(False)), ObjectV(value: FaunaDate(2019-11-12 12:00:00 AM),IsSet: BooleanV(False)), ObjectV(value: RefV(id = "123", collection = RefV(id = "Letters", collection = RefV(id = "collections"))),IsSet: BooleanV(False)), ObjectV(value: DoubleV(10.1),IsSet: BooleanV(False)), ObjectV(value: RefV(id = "double", collection = RefV(id = "functions")),IsSet: BooleanV(False)), ObjectV(value: RefV(id = "letters", collection = RefV(id = "indexes")),IsSet: BooleanV(False)), ObjectV(value: LongV(10),IsSet: BooleanV(False)), ObjectV(value: RefV(id = "1", collection = RefV(id = "keys")),IsSet: BooleanV(False)), ObjectV(value: QueryV(System.Collections.Generic.Dictionary`2[System.String,FaunaDB.Query.Expr]),IsSet: BooleanV(False)), ObjectV(value: NullV,IsSet: BooleanV(False)), ObjectV(value: ObjectV(x: LongV(10)),IsSet: BooleanV(False)), ObjectV(value: RefV(id = "employees", collection = RefV(id = "roles")),IsSet: BooleanV(False)), ObjectV(value: SetRefV(System.Collections.Generic.Dictionary`2[System.String,FaunaDB.Types.Value]),IsSet: BooleanV(True)), ObjectV(value: StringV(ten),IsSet: BooleanV(False)), ObjectV(value: StringV(10),IsSet: BooleanV(False)), ObjectV(value: FaunaTime(2020-07-06T12:34:56.789Z),IsSet: BooleanV(False)), ObjectV(value: RefV(id = "1", collection = RefV(id = "tokens")),IsSet: BooleanV(False)))

System.out.println(
    client.query(
        Map(
            Arr(
                Arr(Value("array")),
                Value(true),
                Value(false),
                Value(new byte[] {0x1, 0x2, 0x3, 0x4}),
                Arr(Value(0x1), Value(0x2), Value(0x3), Value(0x4)),
                Collection("Letters"),
                Ref("credentials/self"),
                Database("child_db"),
                Date("2019-11-12"),
                Ref(Collection("Letters"), "123"),
                Value(10.1),
                Function("double"),
                Index("letters"),
                Value(10),
                Ref(Keys(), "1"),
                Query(Lambda("x", Var("x"))),
                Null(),
                Obj("x", Value(10)),
                Role("employees"),
                Match(Index("letters")),
                Value("ten"),
                Value("10"),
                Time("2020-07-06T12:34:56.789Z"),
                Ref(Tokens(), "1")
            ),
            Lambda(
                "x",
                Obj("value", Var("x"), "IsSet", IsSet(Var("x")))
            )
        )
    ).get());

[{value: ["array"], IsSet: false}, {value: true, IsSet: false}, {value: false, IsSet: false}, {value: [0x01 0x02 0x03 0x04], IsSet: false}, {value: [1, 2, 3, 4], IsSet: false}, {value: ref(id = "Letters", collection = ref(id = "collections")), IsSet: false}, {value: ref(id = "286808707785818624", collection = ref(id = "credentials")), IsSet: false}, {value: ref(id = "child_db", collection = ref(id = "databases")), IsSet: false}, {value: 2019-11-12, IsSet: false}, {value: ref(id = "123", collection = ref(id = "Letters", collection = ref(id = "collections"))), IsSet: false}, {value: 10.1, IsSet: false}, {value: ref(id = "double", collection = ref(id = "functions")), IsSet: false}, {value: ref(id = "letters", collection = ref(id = "indexes")), IsSet: false}, {value: 10, IsSet: false}, {value: ref(id = "1", collection = ref(id = "keys")), IsSet: false}, {value: QueryV({api_version=4, lambda=x, expr={var=x}}), IsSet: false}, {value: null, IsSet: false}, {value: {x: 10}, IsSet: false}, {value: ref(id = "employees", collection = ref(id = "roles")), IsSet: false}, {value: {@set = {match: ref(id = "letters", collection = ref(id = "indexes"))}}, IsSet: true}, {value: "ten", IsSet: false}, {value: "10", IsSet: false}, {value: 2020-07-06T12:34:56.789Z, IsSet: false}, {value: ref(id = "1", collection = ref(id = "tokens")), IsSet: false}]

Map(
  [
    ['array'],
    true,
    false,
    new Uint8Array([1, 2, 3, 4]),
    [0x1, 0x2, 0x3, 0x4],
    Collection('Letters'),
    Ref('credentials/self'),
    Database('child_db'),
    Date('2019-11-12'),
    Ref(Collection('Letters'), 123),
    10.1,
    Function('double'),
    Index('letters'),
    10,
    Ref(Keys(), '1'),
    Query(Lambda('x', Var('x'))),
    null,
    { x: 10 },
    Role('employees'),
    Match(Index('letters')),
    'ten',
    '10',
    Time('2020-07-06T12:34:56.789Z'),
    Ref(Tokens(), '1'),
  ],
  Lambda('x', {
    value: Var('x'),
    IsSet: IsSet(Var('x')),
  })
)

[
  { value: [ 'array' ], IsSet: false },
  { value: true, IsSet: false },
  { value: false, IsSet: false },
  { value: { '0': 1, '1': 2, '2': 3, '3': 4 }, IsSet: false },
  { value: [ 1, 2, 3, 4 ], IsSet: false },
  { value: Collection("Letters"), IsSet: false },
  { value: Ref(Credentials(), "302043979982045696"), IsSet: false },
  { value: Database("child_db"), IsSet: false },
  { value: Date("2019-11-12"), IsSet: false },
  { value: Ref(Collection("Letters"), "123"), IsSet: false },
  { value: 10.1, IsSet: false },
  { value: Function("double"), IsSet: false },
  { value: Index("letters"), IsSet: false },
  { value: 10, IsSet: false },
  { value: Ref(Keys(), "1"), IsSet: false },
  { value: Query(Lambda("x", Var("x"))), IsSet: false },
  { value: null, IsSet: false },
  { value: { x: 10 }, IsSet: false },
  { value: Role("employees"), IsSet: false },
  { value: Match(Index("letters")), IsSet: true },
  { value: 'ten', IsSet: false },
  { value: '10', IsSet: false },
  { value: Time("2020-07-06T12:34:56.789Z"), IsSet: false },
  { value: Ref(Tokens(), "1"), IsSet: false }
]

Query metrics:

bytesIn: 594
bytesOut: 1,511
computeOps: 2
readOps: 0
writeOps: 0
readBytes: 373
writeBytes: 0
queryTime: 23ms
retries: 0

This query operates on a pre-existing schema, which is not provided here.

Also, the query is executed via a client connection, that uses a secret acquired by calling the Login function (not shown here), so that Ref("credentials/self") returns a valid value.

Is this article helpful?

Tell Fauna how the article can be improved:
Visit Fauna's forums or email docs@fauna.com

Thank you for your feedback!

IsSet

Description

Parameters

Returns

Examples

Related functions

`IsSet`