BUG: bulk copy into table with computed columns fails and also reports incorrect number of rows copied

The core issue here stems from default ANSI_NULLS and other options that are incompatible with bulk copy into tables with computed columns. Providing a means to change these from their current defaults is the only way to allow copy into a table with computed columns (see https://learn.microsoft.com/en-us/sql/t-sql/statements/set-ansi-nulls-transact-sql?view=sql-server-ver16)

To reproduce:

Create a DB table with one or more calculated columns e.g.:
```
CREATE TABLE mytest(
f1 integer,
f2 as  (f1+1) PERSISTED
)
```
Create a test file:
```
echo '1,1' > test.csv
```

Attempt to BCP:

freebcp mytest in test.csv -S xxx -U xxx -P xxx -D xxx -c -t ,

This gives the following message, including the inaccurate one about a row being copied (in reality, no rows are copied):

Starting copy...
Msg 1934, Level 16, State 1
Server 'EC2AMAZ-KR4REND', Line 1
    INSERT failed because the following SET options have incorrect settings: 'ANSI_NULLS, QUOTED_IDENTIFIER, CONCAT_NULL_YIELDS_NULL, ANSI_WARNINGS, ANSI_PADDING'. Verify that SET options are correct for use with indexed views and/or indexes on computed columns and/or filtered indexes and/or query notifications and/or XML data type methods and/or spatial index operations.
Msg 20018, Level 16
General SQL Server error: Check messages from the SQL Server

1 rows copied.

Solution:

This issue can be solved using free-form SET commands:

            const char *set2017defaults =
              "SET ANSI_NULLS ON;"
              "SET QUOTED_IDENTIFIER ON;"
              "SET CONCAT_NULL_YIELDS_NULL ON;"
              "SET ANSI_PADDING ON;"
              "SET ANSI_WARNINGS ON;"
              "SET ARITHABORT ON;"
              "SET NUMERIC_ROUNDABORT OFF;"
              ;
            if(dbcmd(dbproc, set2017defaults) == FAIL || dbsqlexec(dbproc) == FAIL)
            fprintf(stderr, "Unable to set default options\n");
          else {
            dbcancel(data.dbproc);

            // continue with bulk load
          }

Proposed change:

Although a workaround as shown above can be used, it would be better if these settings a) were default and b) could be modified in a manner similar to the bcp_control KEEPIDENTITY option. I would be happy to contribute a pull request reflecting the above. I would be happy to submit a PR if helpful

FreeTDS / freetds