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https://issues.apache.org/jira/browse/CALCITE-2921?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16899523#comment-16899523
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Julian Hyde commented on CALCITE-2921:
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OK, if you think that CALCITE-2302 fully fixes this issue, we can go with that.
Note that in cases like {{NULLIF(NULL, y)}} or {{AVG(NULL)}} it may be
difficult or impossible to deduce the type of the NULL from other arguments. So
maybe we need a hybrid of 2302 and 2921. Can you work on getting that into 1.21
[~danny0405]? If you don't have time, let's commit the fix we have (it's ready
to go on https://github.com/julianhyde/calcite/tree/2921-naked-nulls) and
improve it later.
The plan improvements noted by [~kgyrtkirk] in this PR were because several
NULL:null values became NULL:boolean because of better type deduction of
internally-created RexNodes. But a better solution is to disallow people
calling RelBuilder.literal(null) or RexBuilder.constantNull(). I did this in
[b432756|https://github.com/julianhyde/calcite/commit/b432756e2be9ad0557a56254550eb4438dd0efcf],
and will push this to master shortly.
> Allow NULL as argument to function calls
> ----------------------------------------
>
> 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: Julian Hyde
> Priority: Critical
> Labels: pull-request-available
> Fix For: 1.21.0
>
> Time Spent: 1.5h
> Remaining Estimate: 0h
>
> Currently {{nullif(null,y)}} throws exception in verification. This is
> because translates {{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!
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