Exists

Exists( ref, [ts] )
Exists( ref, [ts] )
Exists( ref, [ts] )
Exists( ref, [ts] )
exists( ref, [ts]
Exists( ref, [ts] )

Description

The Exists function returns boolean true if the provided ref exists at the specified timestamp (in the case of a document), or is non-empty (in the case of a set), and false otherwise.

Parameters

Parameter Type Definition and Requirements

ref

Reference

The Reference that uniquely identifies a document within the database.

ts

Long or Timestamp

Optional - The timestamp at which the existence of the Reference is checked. Can be expressed as either a number of UNIX microseconds since epoch, or as a Timestamp. Defaults to the current time.

For large values of ts (positive or negative), you may need to express the value in a String to maintain numeric precision (Fauna uses 64-bit signed integers, whereas JavaScript uses 53-bit signed integers).

Returns

A boolean value

Examples

The following query checks for the existence of a ref pointing at a document in the spells collection at value 181388642046968320L. Since this ref is present at the current time, true is returned.

try
{
    Value result = await client.Query(
        Exists(Ref(Collection("spells"), "181388642046968320"))
    );
    Console.WriteLine(result);
}
catch (Exception e)
{
    Console.WriteLine($"ERROR: {e.Message}");
}
BooleanV(True)
result, err := client.Query(
	f.Exists(f.Ref(f.Collection("spells"), "181388642046968320")))

if err != nil {
	fmt.Fprintln(os.Stderr, err)
} else {
	fmt.Println(result)
}
true
System.out.println(
    client.query(
        Exists(
            Ref(Collection("spells"), Value("181388642046968320"))
        )
    ).get());
true
client.query(
  q.Exists(
    q.Ref(q.Collection('spells'), '181388642046968320')
  )
)
.then((ret) => console.log(ret))
.catch((err) => console.error(
  'Error: [%s] %s: %s',
  err.name,
  err.message,
  err.errors()[0].description,
))
true
result = client.query(
  q.exists(q.ref(q.collection("spells"), "181388642046968320"))
)
print(result)
True
Exists(
  Ref(Collection('spells'), '181388642046968320')
)
true
Query metrics:

  •    bytesIn:  68

  •   bytesOut:  17

  • computeOps:   1

  •    readOps:   1

  •   writeOps:   0

  •  readBytes: 112

  • writeBytes:   0

  •  queryTime: 4ms

  •    retries:   0

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!