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database.exists()

Learn: Databases and multi-tenancy

Test if a child database exists.

Signature

exists() => Boolean

Description

Tests if a child database, represented as an Database document, exists. The parent database is the database to which the query’s the authentication secret is scoped.

Using database.create() to check the existence of a top-level database is not supported.

Fauna stores child databases as documents in the parent database’s Database system collection. Database documents have the DatabaseDef type.

exists() vs. null comparisons

You can use either exists() or a null comparison (== null or != null) to check the existence or validity of a value. For example:

Database.byName("childDB").exists() // true

Database.byName("childDB") != null  // true

Key differences:

  • exists() returns an error if called on an unsupported value.

  • Null comparisons do not throw errors and work safely on any value.

For example:

// Declare an object. Objects don't support
// an `exists()` method.
let object = { a: "Foo", b: "Bar" }

object.exists()  // Returns `invalid_query` error

object != null   // Returns true

Parameters

None

Return value

Type Description

Boolean

If true, the Database document exists. If false, the Database document doesn’t exist.

Examples

Database.byName("childDB").exists()
true
Database.byName("noChildDB").exists()
false

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