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https://issues.apache.org/jira/browse/FLINK-7959?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16265081#comment-16265081
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ASF GitHub Bot commented on FLINK-7959:
---------------------------------------

Github user twalthr commented on a diff in the pull request:

    https://github.com/apache/flink/pull/4940#discussion_r152924498
  
    --- Diff: 
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/codegen/calls/CurrentTimePointCallGen.scala
 ---
    @@ -31,28 +32,28 @@ class CurrentTimePointCallGen(
       extends CallGenerator {
     
       override def generate(
    -      codeGenerator: CodeGenerator,
    -      operands: Seq[GeneratedExpression])
    -    : GeneratedExpression = targetType match {
    +      ctx: CodeGeneratorContext,
    --- End diff --
    
    Use `ExprCodeGenerator` here such that we don't need to pass `nullCheck` to 
every util function, if those functions are part of `ExprCodeGenerator` class. 
With this approach we don't need to add `nullCheck` to `CallGenerate.generate`.


> Split CodeGenerator into CodeGeneratorContext and ExprCodeGenerator
> -------------------------------------------------------------------
>
>                 Key: FLINK-7959
>                 URL: https://issues.apache.org/jira/browse/FLINK-7959
>             Project: Flink
>          Issue Type: Improvement
>          Components: Table API & SQL
>            Reporter: Kurt Young
>            Assignee: Kurt Young
>
> Right now {{CodeGenerator}} actually acts two roles, one is responsible for 
> generating codes from RexNode, and the other one is keeping lots of reusable 
> statements. It makes more sense to split these logic into two dedicated 
> classes. 
> The new {{CodeGeneratorContext}} will keep all the reusable statements, while 
> the new {{ExprCodeGenerator}} will only do generating codes from RexNode.
> And for classes like {{AggregationCodeGenerator}} or 
> {{FunctionCodeGenerator}}, I think the should not be the subclasses of the 
> {{CodeGenerator}}, but should all as standalone classes. They can create 
> {{ExprCodeGenerator}} when they need to generating codes from RexNode, and 
> they can also generating codes by themselves. The {{CodeGeneratorContext}} 
> can be passed around to collect all reusable statements, and list them in the 
> final generated class.



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