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Version: v2.x

Schema/Metadata API Reference: Run SQL (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.

run_sql

run_sql can be used to run arbitrary SQL statements.

Multiple SQL statements can be separated by a ;, however, only the result of the last SQL statement will be returned.

Admin-only

This is an admin-only request, i.e. the request can only be executed with X-Hasura-Role: admin. This can be set by passing X-Hasura-Admin-Secret or by setting the right role in webhook/JWT authorization mode.

This is deliberate as it is hard to enforce any sort of permissions on arbitrary SQL. If you find yourself in the need of using run_sql to run custom DML requests, consider creating a view. You can now define permissions on that particular view for various roles.

Use cases

  1. To execute DDL operations that are not supported by the console (e.g. managing indexes).
  2. Run custom DML requests from backend microservices instead of installing libraries to speak to Postgres.

An example:

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

{
"type": "run_sql",
"args": {
"sql": "CREATE UNIQUE INDEX ON films (title);"
}
}

While run_sql lets you run any SQL, it tries to ensure that the Hasura GraphQL engine's state (relationships, permissions etc.) is consistent i.e. you cannot drop a column on which any metadata is dependent on (say a permission or a relationship). The effects, however, can be cascaded.

Example: If we were to drop the 'bio' column from the author table (let's say the column is used in some permission), you would see an error.

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

{
"type": "run_sql",
"args": {
"sql": "ALTER TABLE author DROP COLUMN name"
}
}
HTTP/1.1 400 BAD REQUEST
Content-Type: application/json

{
"path": "$.args",
"error": "cannot drop due to the following dependent objects : permission author.user.select"
}

We can however, cascade these changes.

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

{
"type": "run_sql",
"args": {
"sql": "ALTER TABLE author DROP COLUMN bio",
"cascade" : true
}
}
HTTP/1.1 200 OK
Content-Type: application/json

{
"result_type": "CommandOk"
}

With the above request, the dependent permission is also dropped.

Example: If we were to drop a foreign key constraint from the article table (let's say the column involved in the foreign key is used to define a relationship), you would see an error.

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

{
"type": "run_sql",
"args": {
"sql": "ALTER TABLE article DROP CONSTRAINT article_author_id_fkey"
}
}
HTTP/1.1 400 BAD REQUEST
Content-Type: application/json

{
"path": "$.args",
"error": "cannot drop due to the following dependent objects : constraint article.article_author_id_fkey"
}

We can however, cascade these changes.

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

{
"type": "run_sql",
"args": {
"sql": "ALTER TABLE article DROP CONSTRAINT article_author_id_fkey",
"cascade" : true
}
}
HTTP/1.1 200 OK
Content-Type: application/json

{
"result_type": "CommandOk"
}

With the above request, the dependent permission is also dropped.

In general, the SQL operations that will affect Hasura metadata are:

  1. Dropping columns
  2. Dropping tables
  3. Dropping foreign keys
  4. Altering types of columns
  5. Dropping SQL functions
  6. Overloading SQL functions

In case of 1, 2 and 3 the dependent objects (if any) can be dropped using cascade. However, when altering type of columns, if any objects are affected, the change cannot be cascaded. So, those dependent objects have to be manually dropped before executing the SQL statement. Dropping SQL functions will cascade the functions in metadata even without using cascade since no other objects depend on them. Overloading tracked SQL functions is not allowed.

Set check_metadata_consistency field to false to force the server to not consider metadata dependencies.

Args syntax

KeyRequiredSchemaDescription
sqltrueStringThe sql to be executed
cascadefalseBooleanWhen set to true, the effect (if possible) is cascaded to any hasuradb dependent objects (relationships, permissions, templates).
check_metadata_consistencyfalseBooleanWhen set to false, the sql is executed without checking metadata dependencies.
read_onlyfalseBooleanWhen set to true, the request will be run in READ ONLY transaction access mode which means only select queries will be successful. This flag ensures that the GraphQL schema is not modified and is hence highly performant.

Response

The response is a JSON Object with the following structure.

KeyAlways presentSchemaDescription
result_typetrueStringOne of "CommandOk" or "TuplesOk"
resultfalse[[Text]] (An array of rows, each row an array of columns)This is present only when the result_type is "TuplesOk"
Note

The first row in the result (when present) will be the names of the columns.

Some examples

An SQL query returning results.

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

{
"type": "run_sql",
"args": {
"sql": "select user_id, first_name from author limit 2;"
}
}
HTTP/1.1 200 OK
Content-Type: application/json

{
"result_type": "TuplesOk",
"result": [
[
"user_id",
"first_name"
],
[
"1",
"andre"
],
[
"2",
"angela"
]
]
}

An SQL query to create a table:

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

{
"type":"run_sql",
"args": {
"sql": "create table item ( id serial, name text, category text, primary key (id))",
"check_metadata_consistency": false
}
}
HTTP/1.1 200 OK
Content-Type: application/json

{
"result_type": "CommandOk",
"result": null
}