DB::Exception: Newly added column B has a default expression, so adding expressions that use it to the sorting key is forbidden.

[den-crane]

create table mx(A Int64) Engine=MergeTree order by A;

alter table mx add column B Int64 default 111, modify order by (A,B);

DB::Exception: Newly added column B has a default expression, so adding expressions that use it to the sorting key is forbidden.

This behaviour has no sense. I don't see a reason why it's forbidden.

Moreover there is a workaround:

alter table mx add column B Int64 , modify order by (A,B);
alter table mx modify column B default 111;

[filimonov]

Non constant DEFAULT can require reordering of existing data, that's why it's forbidden.

Constant DEFAULTs actually may be allowed.

[jlazdw]

Hi: I have an application that requires adding new columns with Constant Default Values and these columns are used for order-by key expression. Given the above comment on "Constant DEFAULTs actually may be allowed.", can the current code in MergeTreeData.cpp, https://github.com/ClickHouse/ClickHouse/blob/master/src/Storages/MergeTree/MergeTreeData.cpp#L364, be fixed to reflect the above logic, that is, if the default expression of the column only contains constant expression, then no exception gets thrown. Currently, the code has:

if (new_metadata.columns.getDefaults().count(col)) throw Exception("Newly added column " + backQuoteIfNeed(col) + " has a default expression, so adding " "expressions that use it to the sorting key is forbidden", ErrorCodes::BAD_ARGUMENTS)

If the fix is feasible, when can I get it from the future ClickHouse release?