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From Julian Hyde <jh...@apache.org>
Subject Re: SQL dialect specific functionality
Date Fri, 23 Feb 2018 22:15:50 GMT
Yes. The general pattern is to add a ‘boolean supportsXxx()’ method to SqlDialect, and
make the JdbcYyyRule not generate a JdbcYyy if the relational expression contains an xxx and
this particular dialect does not support it. Then add a test to RelToSqlConverterTest that
covers several dialects.

(In this case xxx = windowed aggregates, and yyy = Project.)

Julian


> On Feb 22, 2018, at 2:53 AM, Pavel Gubin <pgubin@icloud.com> wrote:
> 
> Not all JDBC datasources support window functions. But JdbcProject is generated regardless
of this fact. In the result we get SQL with window function which gives an error when the
execution is pushed to the JDBC datasource. What is the best way to avoid such errors based
on SQL dialect? Avoid converting to JdbcProject if some unsupported features are used?
> 
> Pavel


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