On 2018/05/07 08:39:00, "Yuzhao Chen (JIRA)" <[email protected]> wrote:
> Yuzhao Chen created CALCITE-2302:
> ------------------------------------
>
> Summary: Implicit type cast support
> Key: CALCITE-2302
> URL: https://issues.apache.org/jira/browse/CALCITE-2302
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.17.0
> Reporter: Yuzhao Chen
> Assignee: Julian Hyde
> Fix For: 1.17.0
>
>
> Now many BDs have support implicit type cast, eg: SqlServer, Oracle, Hive.
>
> Implicit type cast is an useful function for many cases, So we should support
> this.
>
> I checkout Calcite code and found that:
> # Now we use a validator to validate our operands types[ through kinds of
> namespaces and scopes ]
> # Most of the validations will finally goes to
> {code:java}
> SqlOperator.validateOperands
> {code}
> # which will use validation logic defined in corresponding
> SqlOperandTypeChecker
>
> What i'm confused about is where should i put the implicit type cast logic in
> ? There are several ways i figured out:
> # Supply a tool class/rules to add casts into a parsed SqlNode tree which
> will then go through the validation logic later on.
> # Unleash the validation logic in kinds of SqlOperandTypeChecker, then modify
> the RelNode/RexNodes tree converted from a validated SqlNode tree to add in
> casts.
>
> So guys, i need your help, which of the 2 ways should i go, or if there are
> better way to do this?
>
>
>
>
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> hi, guys, i have made a PR for it https://github.com/apache/calcite/pull/706,
> really appreciate your suggestions.
