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')