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https://issues.apache.org/jira/browse/CALCITE-2673?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16687166#comment-16687166
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Julian Hyde commented on CALCITE-2673:
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The JIRA case title and commit message don't make it clear whether "supports
all functions by default" is a good thing or a bad thing, and what the change
is. Please clarify it.
Can we give people guidance for how they would override? The solution for
Jethro was messy because it had to connect to an actual instance and ask the
server what functions it supported. That mess seems inevitable because we want
to share dialect instances across connections.
> SqlDialect supports pushing of all functions by default
> -------------------------------------------------------
>
> Key: CALCITE-2673
> URL: https://issues.apache.org/jira/browse/CALCITE-2673
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Reporter: Jesus Camacho Rodriguez
> Assignee: Jesus Camacho Rodriguez
> Priority: Major
> Fix For: 1.18.0
>
>
> SqlDialect contains a 'supportsFunction' that can be used by rules to know
> whether a certain function is supported in the given dialect, e.g., to choose
> whether to push a Filter expression to JDBC, etc.
> The default implementation of 'supportsFunction' always returns true.
> I believe a better idea would be to support in the default implementation for
> the method the most common SQL functions. Then each dialect can override that
> behavior and expand/limit the supported functions, e.g., JethroDataDialect
> already does that.
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