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