Query execution
Run a read operation against a GraphQL schema and return the requested fields.
GraphQL · Function
execute
GraphQL execution runs a parsed and validated operation against a schema. It resolves requested fields, completes their values, and returns data shaped like the client’s operation, potentially with errors.
How it works
Execution runs a validated GraphQL operation against an existing schema. It starts at the root Query, Mutation, or Subscription fields, invokes resolvers for requested fields, completes nested selections or scalar values, and produces a response that mirrors the query shape; resolvers can perform asynchronous work.
Syntax
execute(schema, document, operationName, variableValues, initialValue)Returns
A GraphQL response whose data mirrors the requested operation; it may also include errors and extensions.
Key points
- Execution follows parsing and validation; the server runs only after the document passes those earlier phases.
- The operation type selects the root object from which field resolution starts.
- Resolvers are the server-defined functions that supply values for schema fields.
- Resolver implementations may perform asynchronous work, so execution supports asynchronous data retrieval.
- Leaf results are coerced to the schema's declared scalar types before they are returned.
- Response keys come from field names or aliases, preserving the requested response structure.
Example: Executing a GraphQL operation
const result = await graphql({
schema,
source: '{ hello }',
rootValue: { hello: 'world' }
});
console.log(result.data);A server executes the parsed and validated operation against its schema and returns data shaped like the request.
When to use it
Mutation execution
Apply server-side state changes through a mutation's root fields.
Subscription execution
Resolve event-driven subscription operations and produce results for events.
Shape-preserving responses
Assemble nested response objects whose keys match fields or aliases in the operation.
Interview questions
QHow does GraphQL execution produce a response?
Execution begins with the operation's root type: Query, Mutation, or Subscription. The executor resolves requested fields, recursively completes object selections, and coerces leaf values to the schema's expected types.
Follow-up: How can a response contain both data and errors? A field resolver may fail after other fields have resolved, allowing partial data while the failure is reported in errors.
QWhat role do field resolvers play during execution?
Each requested field is backed by a resolver. The resolver receives the relevant parent value and produces the next value; that value is then completed either by running a nested selection set or by coercing a scalar.
Follow-up: What happens for an asynchronous resolver? Execution can await asynchronous resolver results before completing the field and assembling the response.
QHow is the response shape determined?
The result is assembled as a key-value map while fields resolve. A field name, or its alias when one is present, becomes the key, so the returned structure mirrors the client's requested shape.
Follow-up: Why are aliases significant? They let multiple selections use distinct response keys even when they refer to fields with the same underlying name.
Related
QueriesMutationsSubscriptionsResolversResponse