Masking Job Fails with: Cannot be modified because it is either a computed column or is the result of a UNION operator (KBA10286)

Issue

A Microsoft SQL Server masking job may fail with the following error message:

2023/01/01 01:30:00 - DelphixTableInsert.0 - Error updating batch
2023/01/01 01:30:00 - DelphixTableInsert.0 - The column "Column_1" cannot be modified because it is either a computed column or is the result of a UNION operator.

This can affect both On-the-Fly and In-place masking.

It is not possible to INSERT or UPDATE data into a computed column. It is not possible to mask a computed column as it is a virtual column, also know as an expression of a column. 

There is more information on what a computed column here on SQL Server help: http://www.sql-server-helper.com/error-messages/msg-271.aspx

Applicable Delphix Versions

Click here to view the versions of the Delphix engine to which this article applies

Date	Release
Jul 24, 2023	13.0.0.0
Jun 21, 2023	12.0.0.0
May 25, 2023	11.0.0.0
Apr 13, 2023	10.0.0.0 | 10.0.0.1
Mar 13, 2023 | Mar 20, 2023	9.0.0.0 | 9.0.0.1
Feb 13, 2023	8.0.0.0
Jan 12, 2023	7.0.0.0
Releases Prior to 2023
Major Release	All Sub Releases
6.0	6.0.0.0, 6.0.1.0, 6.0.1.1, 6.0.2.0, 6.0.2.1, 6.0.3.0, 6.0.3.1, 6.0.4.0, 6.0.4.1, 6.0.4.2, 6.0.5.0, 6.0.6.0, 6.0.6.1, 6.0.7.0, 6.0.8.0, 6.0.8.1, 6.0.9.0, 6.0.10.0, 6.0.10.1, 6.0.11.0, 6.0.12.0, 6.0.12.1, 6.0.13.0, 6.0.13.1, 6.0.14.0, 6.0.15.0, 6.0.16.0, 6.0.17.0, 6.0.17.1, 6.0.17.2
5.3	5.3.0.0, 5.3.0.1, 5.3.0.2, 5.3.0.3, 5.3.1.0, 5.3.1.1, 5.3.1.2, 5.3.2.0, 5.3.3.0, 5.3.3.1, 5.3.4.0, 5.3.5.0, 5.3.6.0, 5.3.7.0, 5.3.7.1, 5.3.8.0, 5.3.8.1, 5.3.9.0
5.2	5.2.2.0, 5.2.2.1, 5.2.3.0, 5.2.4.0, 5.2.5.0, 5.2.5.1, 5.2.6.0, 5.2.6.1
5.1	5.1.0.0, 5.1.1.0, 5.1.2.0, 5.1.3.0, 5.1.4.0, 5.1.5.0, 5.1.5.1, 5.1.6.0, 5.1.7.0, 5.1.8.0, 5.1.8.1, 5.1.9.0, 5.1.10.0
5.0	5.0.1.0, 5.0.1.1, 5.0.2.0, 5.0.2.1, 5.0.2.2, 5.0.2.3, 5.0.3.0, 5.0.3.1, 5.0.4.0, 5.0.4.1, 5.0.5.0, 5.0.5.1, 5.0.5.2, 5.0.5.3, 5.0.5.4

Resolution

The computed column will need to be excluded in the ruleset.

One method is to use Custom SQL in the ruleset and exclude the computed columns in the select statement. Further information here: RuleSet - Custom SQL

Troubleshooting

Review the info logs for the following error:

The column "Column_1" cannot be modified because it is either a computed column or is the result of a UNION operator.