Casts
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')