database.exists()
| Learn: Databases and multi-tenancy |
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Test if a child database exists.
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 // trueKey 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