Schema/Metadata API Reference: Computed Fields¶
Table of contents
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 |
ComputedFieldDefinition¶
| Key | Required | Schema | Description |
|---|---|---|---|
| function | true | FunctionName | The SQL function |
| table_argument | false | String | Name of the argument which accepts a table row type. If omitted, the first argument is considered a table argument |
| session_argument | false | String | Name of the argument which accepts the Hasura session object as a JSON/JSONB value. If omitted, the Hasura session object is not passed to the function |
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 |
