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Re: [jira] [Created] (CALCITE-2302) Implicit type cast support

On 2018/05/07 08:39:00, "Yuzhao Chen (JIRA)" <jira@xxxxxxxxxx> 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.