I am trying to create an index on a view that references a table with a masked column (SQL Server 2016). The masked column is not the only one in that table and it's not used in the view.

create unique clustered index [IX_Name]
on dbo.vw_ViewName(SomeUniqueId)

I get this error:

The index on view 'dbo.vw_ViewName' cannot be created because the view is referencing table 'dbo.TableName' with masked columns.

In another environment, where masking is not enabled, the index is created successfully.

I looked through about four pages of Google results and haven't found any sensible description of the error. I would appreciate any knowledge transfer on the error and why it is not possible to create such index.

Here is some SQL to reproduce the issue:

drop view if exists dbo.vw_Aggregate
drop table if exists dbo.MainTable
drop table if exists dbo.SecondaryTable
go

create table dbo.MainTable
(
    MainTableId uniqueidentifier primary key,
    SomeExternalId uniqueidentifier,
    SecondaryTableId uniqueidentifier
)
go

create table dbo.SecondaryTable
(
    SecondaryTableId uniqueidentifier primary key,
    CreatedOn datetime,
    Amount decimal(19, 8),
    
    -- the below column produces error,
    -- if commented out - there is no error
    [Description] nvarchar(max) masked with (function = 'default()'),
 
    Dummy int
)
go

create view dbo.vw_Aggregate with schemabinding
as
(
    select AggregateId = m.MainTableId,
           m.SomeExternalId,
           s.CreatedOn,
           s.Amount
    from dbo.MainTable m
    inner join dbo.SecondaryTable s on s.SecondaryTableId = m.SecondaryTableId
)
go

create unique clustered index [IX_dbo.vw_Aggregate(AggregateId)]
on dbo.vw_Aggregate(AggregateId)
go

I am trying to create an index on a view that references a table with a masked column (SQL Server 2016). The masked column is not the only one in that table, and it's not used in the view.

create unique clustered index [IX_Name]
on dbo.vw_ViewName(SomeUniqueId)

I get this error:

The index on view 'dbo.vw_ViewName' cannot be created because the view is referencing table 'dbo.TableName' with masked columns.

In another environment, where masking is not enabled, the index is created successfully.

I looked through about four pages of Google results and haven't found any sensible description of the error. I would appreciate any knowledge transfer on the error and why it is not possible to create such index.

Here is some SQL to reproduce the issue:

drop view if exists dbo.vw_Aggregate
drop table if exists dbo.MainTable, dbo.SecondaryTable
go

create table dbo.MainTable
(
    MainTableId uniqueidentifier primary key,
    SomeExternalId uniqueidentifier,
    SecondaryTableId uniqueidentifier
)
go

create table dbo.SecondaryTable
(
    SecondaryTableId uniqueidentifier primary key,
    CreatedOn datetime,
    Amount decimal(19, 8),
    -- the below column produces error,
    -- if commented out - there is no error
    [Description] nvarchar(max) masked with (function = 'default()'),
    Dummy int
)
go

create view dbo.vw_Aggregate with schemabinding
as
    select AggregateId = m.MainTableId,
           m.SomeExternalId,
           s.CreatedOn,
           s.Amount
    from dbo.MainTable m
    inner join dbo.SecondaryTable s on s.SecondaryTableId = m.SecondaryTableId
go

create unique clustered index [IX_dbo.vw_Aggregate(AggregateId)]
on dbo.vw_Aggregate(AggregateId)
go