[jira] [Comment Edited] (CALCITE-2921) nullif(null,y) throws exception in verification

["Hongze Zhang (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-2921?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16844657#comment-16844657 ] 

Hongze Zhang edited comment on CALCITE-2921 at 5/21/19 9:09 AM:
----------------------------------------------------------------

Is functionality of the new added method {{SqlTypeTransforms#nullToDefault}} overlapping {{SqlOperandTypeInference}}?


was (Author: zhztheplayer):
Is functionality of the new added method {{SqlTypeTransforms#nullToDefault}} overlaps {{SqlOperandTypeInference}}?

> nullif(null,y)  throws exception in verification
> ------------------------------------------------
>
>                 Key: CALCITE-2921
>                 URL: https://issues.apache.org/jira/browse/CALCITE-2921
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 1.18.0
>            Reporter: pengzhiwei
>            Assignee: pengzhiwei
>            Priority: Critical
>              Labels: pull-request-available
>             Fix For: 1.20.0
>
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> Currently calcite will translate "nullif(x,y)" to a case-when expression,just like "case when x = y then null else x".So when "x" is null literal,a exception throws out as follow:
> {code:java}
>  ELSE clause or at least one THEN clause must be non-NULL
> {code}
> I have test in mysql,"nullif(null,y) works well.So I think we should allow this usage of  "nullif".
> There are two ways to fix this issue:
> 1)  Skip the check for "foundNotNull" in SqlCaseOperator#checkOperandTypes:     
> {code:java}
> if (!foundNotNull) {
>   // according to the sql standard we can not have all of the THEN
>   // statements and the ELSE returning null
>   if (throwOnFailure) {
>     throw callBinding.newError(RESOURCE.mustNotNullInElse());
>   }
>   return false;
> }{code}
> However, as the comment says, we cannot have all of the THEN and ELSE returning null.
> 2) Disable the translation from nullif to case-when and keep "nullif" as it is.
> Any suggestion is welcomed,Thanks!



--
This message was sent by Atlassian JIRA
(v7.6.3#76005)