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https://issues.apache.org/jira/browse/CALCITE-4963?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17464813#comment-17464813
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Julian Hyde commented on CALCITE-4963:
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(Thanks for the niceties!)
Let me push back on this, to see whether there's a simpler solution to your
problem. The {{SqlDialectFactory}} interface has only one method,
{{create(DatabaseMetaData)}}, so we figured that it would be fairly easy for
people to create their own factories.
Now, is there some specific logic that is locked inside
{{SqlDialectFactoryImpl}} that you need in your factory? For example, logic to
go from a {{DatabaseMetaData}} to a {{SqlDialect.Context}}? If so, we could
consider moving that logic into a {{public static}} method.
Did you consider using a chain-of-responsibility pattern? Your dialect factory
would try to create a dialect, and if it cannot, it calls {{delegate.create}},
where {{delegate}} is a field that points to the next factory in the chain,
probably {{SqlDialectFactoryImpl.INSTANCE}}.
As part of your PR, can you provide a test? For example, create a dialect
factory that creates a different dialect object for MySQL version 3 and
earlier, and delegates to the default factory for other databases or versions.
> Extensibility of SqlDialectFactory lacks reusability of
> SqlDialectFactoryImpl.*
> -------------------------------------------------------------------------------
>
> Key: CALCITE-4963
> URL: https://issues.apache.org/jira/browse/CALCITE-4963
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Reporter: Marco Jorge
> Priority: Major
> Labels: pull-request-available
> Time Spent: 10m
> Remaining Estimate: 0h
>
> _(nicetities first - great project and thanks all for the great work)_
> Although it's possible to extend the SqlDialectFactory, the custom
> implementation cannot reuse any of the behaviour of the default
> SqlDialectFactoryImpl. The default SqlDialectFactoryImpl has lots of
> important/reusable behaviour such as #getCasing, #isCaseSensitive,
> #getNullCollation or even the default decisioning in the #create method.
> If any user needs to provide a custom SqlDialect yet still support the
> existing SqlDialects the user needs to copy the whole SqlDialectFactoryImpl
> to make the custom changes.
> This request is to make the default behavior in SqlDialectFactoryImpl
> reusable so that extensions don't need to fork a whole class.
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