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https://issues.apache.org/jira/browse/CALCITE-6281?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17820926#comment-17820926
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Julian Hyde commented on CALCITE-6281:
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The only goal is to compare specifications: given an expression, do Calcite and
D (a database implementing dialect X) return the same results? (Stretch goal:
make sure that the results have the same type, modulo differences in the type
systems; make sure that Calcite gives an error if and only if D gives an error.)
> Add test infrastructure to ensure that Calcite is consistent with the SQL
> dialects it is trying to emulate
> ----------------------------------------------------------------------------------------------------------
>
> Key: CALCITE-6281
> URL: https://issues.apache.org/jira/browse/CALCITE-6281
> Project: Calcite
> Issue Type: Improvement
> Reporter: Julian Hyde
> Priority: Major
>
> Add test infrastructure to ensure that Calcite is consistent with the SQL
> dialects it is trying to emulate.
> Calcite is able to emulate other SQL dialects. For example, it can pretend to
> be MySQL by setting "lib=mysql, lex=mysql, conformance=mysql_5". In that
> mode, the user would expect there to be a SUBSTR function, and that
> {{SUBSTR('abc' FROM 0)}} would [return the empty string, the same as
> MySQL|https://github.com/apache/calcite/blob/022d878a73dec796bb72743804a6dded7c239bd3/testkit/src/main/java/org/apache/calcite/test/SqlOperatorTest.java#L9428].
> (On Postgres, the same expression returns 'abc'.)
> How do we trust that MySQL does indeed have that behavior? How do we find out
> if, in a later release, the MySQL team decides to change the behavior. That
> is the goal of this case.
> We propose to add tests that run expressions on both MySQL and
> Calcite-pretending-to-be-MySQL, and ensure that the result is the same on
> both. We use
> [testContainers|https://github.com/testcontainers/testcontainers-java] to
> instantiate, via Docker, and instance of MySQL.
> See discussion [Ensuring that Calcite is consistent with other SQL
> systems|https://lists.apache.org/thread/mxy9p6cy8sssf1sq3gz7zkzm6hsysns5].
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