Schema/Metadata API Reference: Computed Fields (Deprecated)

Deprecation

In versions v2.0.0 and above, the schema/metadata API is deprecated in favour of the schema API and the metadata API.

Though for backwards compatibility, the schema/metadata APIs will continue to function.

Introduction

computed field is an extra field added to a table, its value is computed via an SQL function which has the table row type as an input argument. Currenty, the Hasura GraphQL engine supports functions returning base types or table row types as computed fields.

add_computed_field

add_computed_field is used to define a computed field in a table. There cannot be an existing column or relationship or computed field with the same name.

Create a computed field called full_name on an author table, using an SQL function called author_full_name:

POST /v1/query HTTP/1.1
Content-Type: application/json
X-Hasura-Role: admin

{
    "type":"add_computed_field",
    "args":{
        "table":{
            "name":"author",
            "schema":"public"
        },
        "name":"full_name",
        "definition":{
            "function":{
                "name":"author_full_name",
                "schema":"public"
            },
            "table_argument":"author_row"
        }
    }
}

Args syntax

Key	Required	Schema	Description
table	true	TableName	Name of the table
name	true	ComputedFieldName	Name of the new computed field
definition	true	ComputedFieldDefinition	The computed field definition
comment	false	text	comment

drop_computed_field

drop_computed_field is used to drop a computed field of a table. If there are other objects dependent on this computed field, like permissions, the request will fail and report the dependencies unless cascade is set to true. If cascade is set to true, the dependent objects are also dropped.

Drop a computed field full_name from a table author:

POST /v1/query HTTP/1.1
Content-Type: application/json
X-Hasura-Role: admin

{
    "type":"drop_computed_field",
    "args":{
        "table":{
            "name":"author",
            "schema":"public"
        },
        "name":"full_name",
        "cascade": false
    }
}

Args syntax

Key	Required	Schema	Description
table	true	TableName	Name of the table
name	true	ComputedFieldName	Name of the computed field
cascade	false	Boolean	When set to true, all the dependent items (if any) on this computed fields are also dropped