= Clickhouse read-only mode =

You need to be careful when you use a read-only Clickhouse user in your APIs. The default read-only mode (readonly = 1) will effectively prevent you from changing any query settings, e.g. join_use_nulls, enable_unaligned_array_join, etc. In order to make this work with the read-only mode, you need to set up the readonly flag to 2 in the users.xml:



With the above in place, your queries will be able to setup query settings yet again.

From the official documentation:

Read-only mode is enabled by the readonly setting (not to confuse with readonly constraint type):

= References =