Issue

Operations on string fields are failing with an error similar to the following:

[Microsoft][ODBC Driver 17 for SQL Server][SQL Server] Cannot resolve collation conflict between "Latin1_General_BIN" and "SQL_Latin1_General_CP1_CI_AS" in the equal operation.

[Microsoft][ODBC Driver 17 for SQL Server][SQL Server] Statement(s) could not be prepared.

Environment

SQL Server Destination

Resolution

One of the three following options can resolve this issue:

1. Change the database_default collation to match that of Fivetran 
2. Account for this COLLATE setting in downstream operations (e.g. JOIN ON fivetran_replicated_table.id COLLATE SQL_Latin1_General_CP1_CI_AS = table.id COLLATE SQL_Latin1_General_CP1_CI_AS)
3. As a very last resort, contact Customer Support who can add a feature flag which allows joins to occur without collation. Only request this if you are 100% confident that all character handling is handled properly in every source.

Cause

This error is caused by incompatible collations. Fivetran uses the Latin1_General_BIN collate encoding setting during syncs so that string comparisons (e.g. JOIN operations) can be performed in a way that handles:

• Case sensitive strings
• Unusual or non-ASCII values

It's usage handles an edge case where a table has a primary key that uses strings (e.g. result of a hash function).

Take two records which have primary keys with the same character representations but use different cases (e.g. 'abc' and 'ABC'). The collate setting Latin1_General_BIN will recognise them as different values as it uses case sensitive encoding.

In contrast, if a setting such as SQL_Latin1_General_CP1_CI_AS is used (which uses case insensitive encoding), it may mark one record as the same as the other (even though it's not). It could also cause a failure similar to the following:

java.lang.RuntimeException: com.microsoft.sqlserver.jdbc.SQLServerException: Violation of PRIMARY KEY constraint 'PK__m_table__3213E83F132AEF4A'. 
Cannot insert duplicate key in object 'test_20201112_1923_14xzddh264qyu1c3b7sjs3yuix.m_table'. The duplicate key value is (abc).