Permissions for queries

Queries in ClickHouse can be divided into several types:

1. Read data queries: SELECT, SHOW, DESCRIBE, EXISTS.
2. Write data queries: INSERT, OPTIMIZE.
3. Change settings queries: SET, USE.
4. DDL queries: CREATE, ALTER, RENAME, ATTACH, DETACH, DROP TRUNCATE.
5. KILL QUERY.

The following settings regulate user permissions by the type of query:

• readonly — Restricts permissions for all types of queries except DDL queries.
• allow_ddl — Restricts permissions for DDL queries.

KILL QUERY can be performed with any settings.

readonly

Restricts permissions for read data, write data and change settings queries.

See how the queries are divided into types above.

Possible values

• 0 — All queries are allowed.
• 1 — Only read data queries are allowed.
• 2 — Read data and change settings queries are allowed.

After setting readonly = 1, the user can’t change readonly and allow_ddl settings in the current session.

When using the GET method in the HTTP interface, readonly = 1 is set automatically. To modify data, use the POST method.

Setting readonly = 1 prohibit the user from changing all the settings. There is a way to prohibit the user
from changing only specific settings, for details see constraints on settings.

Default value

0

allow_ddl

Allows/denies DDL queries.

See how the queries are divided into types above.

Possible values

• 0 — DDL queries are not allowed.
• 1 — DDL queries are allowed.

You cannot execute SET allow_ddl = 1 if allow_ddl = 0 for the current session.

Default value

1

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