This section describes introspection of EdgeDB type casts. Features like whether the casts are implicit can be
discovered by introspecting schema::Cast.
Introspection of the schema::Cast:
db> ... ... ... ... ... ... ... ... ... ...
WITH MODULE schema
SELECT ObjectType {
name,
links: {
name,
},
properties: {
name,
}
}
FILTER .name = 'schema::Cast';{
Object {
name: 'schema::Cast',
links: {
Object { name: '__type__' },
Object { name: 'from_type' },
Object { name: 'to_type' }
},
properties: {
Object { name: 'allow_assignment' },
Object { name: 'allow_implicit' },
Object { name: 'id' },
Object { name: 'name' }
}
}
}Introspection of the possible casts from std::int64 to other
types:
db> ... ... ... ... ... ... ...
WITH MODULE schema
SELECT Cast {
allow_assignment,
allow_implicit,
to_type: { name },
}
FILTER .from_type.name = 'std::int64'
ORDER BY .to_type.name;{
Object {
allow_assignment: false,
allow_implicit: true,
to_type: Object { name: 'std::bigint' }
},
Object {
allow_assignment: false,
allow_implicit: true,
to_type: Object { name: 'std::decimal' }
},
Object {
allow_assignment: true,
allow_implicit: false,
to_type: Object { name: 'std::float32' }
},
Object {
allow_assignment: false,
allow_implicit: true,
to_type: Object { name: 'std::float64' }
},
Object {
allow_assignment: true,
allow_implicit: false,
to_type: Object { name: 'std::int16' }
},
Object {
allow_assignment: true,
allow_implicit: false,
to_type: Object { name: 'std::int32' }
},
Object {
allow_assignment: false,
allow_implicit: false,
to_type: Object { name: 'std::json' }
},
Object {
allow_assignment: false,
allow_implicit: false,
to_type: Object { name: 'std::str' }
}
}The allow_implicit property tells whether this is an implicit cast
in all contexts (such as when determining the type of a set of mixed
literals or resolving the argument types of functions or operators if
there’s no exact match). For example, a literal 1 is an
int64 and it is implicitly cast into a bigint
or float64 if it is added to a set containing either one
of those types:
db>
SELECT {1, 2n};{1n, 2n}db>
SELECT {1, 2.0};{1.0, 2.0}What happens if there’s no implicit cast between a couple of scalars in this type of example? EdgeDB checks whether there’s a scalar type such that all of the set elements can be implicitly cast into that:
db>
SELECT INTROSPECT (TYPEOF {<int64>1, <float32>2}).name;{'std::float64'}The scalar types int64 and float32 cannot be
implicitly cast into each other, but they both can be implicitly cast
into float64.
The allow_assignment property tells whether this is an implicit
cast during assignment if a more general implicit cast is not
allowed. For example, consider the following type:
type Example {
property p_int16 -> int16;
property p_float32 -> float32;
property p_json -> json;
}db> ... ... ...
INSERT Example {
p_int16 := 1,
p_float32 := 2
};{Object { id: <uuid>'...' }}db> ... ...
INSERT Example {
p_json := 3 # assignment cast to json not allowed
};InvalidPropertyTargetError: invalid target for property 'p_json' of object type 'default::Example': 'std::int64' (expecting 'std::json')
