[jira] [Commented] (DRILL-203) When you select a null field, things fail rather than returning null

["Jacques Nadeau (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DRILL-203?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13824340#comment-13824340 ] 

Jacques Nadeau commented on DRILL-203:
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The correct solution here has three main parts:

1) In all argument validators, if the allowed incoming type is null, then the argument should validate true if the incoming expression is a NullExpression.INSTANCE.

2) Implement constants expression types that support nullability.  Existing constant expression types do not support nullability so we need to create a similar set that do support nullability.

3) In FunctionImplementationRegistry.getFunction(..), if the incoming expression type is NullExpression, we should be picking the best function to match our need, including supporting implicit casting.  Once a function is picked, for the arguments/operands that are NullExpression, we'll implement them by returning constant child expressions with which are isSet=0 of the required type.  



> When you select a null field, things fail rather than returning null
> --------------------------------------------------------------------
>
>                 Key: DRILL-203
>                 URL: https://issues.apache.org/jira/browse/DRILL-203
>             Project: Apache Drill
>          Issue Type: Bug
>            Reporter: Jacques Nadeau
>




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