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https://issues.apache.org/jira/browse/CALCITE-1913?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16157280#comment-16157280
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Christian Beikov commented on CALCITE-1913:
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I implemented part of what you describe as part of a PR that adds sequence
support. Maybe you could comment on that? [[email protected]]
https://github.com/apache/calcite/pull/514
By allowing a user to provide a custom SqlDialectFactory, a user could make use
of a custom dialect implementation. That way, a consumer of calcite can
overrule if a feature is used or not. Still, the default implementation can
make a decision about whether a feature is used by doing version comparisons.
That obviously requires that SqlDialect is the "gate-keeper" to what a dialect
actually supports rather than handling that through checks against
DatabaseProduct.
My prime example for when the DatabaseProduct approach will break is MySQL.
With version 8 it will support CTEs thus we could push down such SQL, yet we
only have a single MYSQL enum entry. We could introduce multiple entries for
respective versions(e.g. MYSQL5, MYSQL8) to handle such cases, but that won't
handle cases where a user might not want to use a specific feature.
Allowing SqlDialect to handle unparsing or return whether a DBMS has a specific
capability also allows for adding new dialects that don't fit into the current
DatabaseProduct scheme. What if there is a MySQL fork out there that doesn't
support feature X,Y,Z of our "standard MySQL" version we defined through a
DatabaseProduct? These people would be out of luck right now.
Maybe you ([~julianhyde]) could comment further about what he doesn't like
about this approach so we could tackle specifics?
> Include DB version in SqlDialect
> --------------------------------
>
> Key: CALCITE-1913
> URL: https://issues.apache.org/jira/browse/CALCITE-1913
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.13.0
> Reporter: Jess Balint
> Assignee: Jess Balint
> Priority: Minor
>
> It would be useful to have the DB version # in the SqlDialect for unparsing
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