The EnableLegacyParser DSN option, which enables switching between the legacy parser and the new parser, has been deprecated.
The Legacy ODBC SQL parser in the driver understands more of the structure of SQL than it needs to in order to perform the transformations required by the ODBC specification. This means that if there are changes anywhere in the subset of SQL that the parser recognizes, then the parser also has to be changed. Another consequence is that the parser grows unnecessarily, which impacts performance both in terms of memory for parse tables and time for syntax analysis.
For every addition or update to SQL syntax in the database, the legacy parser must also be updated. This activity consumes a considerable amount of time in every release.
The legacy parser is capped to ODBC Driver for Teradata 15.00, and no 15.10 features were supported. So it is strongly advised to retain the default value for this option when using the ODBC driver against DBS 15.10 and later.
Support for the capped legacy parser will be maintained for a period, but will be unavailable in the ODBC Driver for Teradata 18.00.