[jira] [Comment Edited] (CALCITE-4219) Clarify SqlCall#getOperandList() nullability

["Vladimir Sitnikov (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-4219?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17189643#comment-17189643 ] 

Vladimir Sitnikov edited comment on CALCITE-4219 at 9/2/20, 7:17 PM:
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{quote} The other option is to accept that the rules are different for different operators{quote}

Which is "workaround" I mention: we could document that {{getOperandList()}} could have null values in the list, we could document that {{operand(int)}} could return {{null}} even though the methods look like non-nullable.

The methods are very popular, however, their documentation is empty (no javadoc at all), and it is not obvious if nulls are possible there or not.


was (Author: vladimirsitnikov):
{quote} The other option is to accept that the rules are different for different operators{quote}

Which is "workaround" I mention: we could document that {{getOperandList()}} could have null values in the list, we could document that {{operand(int)}} could return {{null}} even though the method.

The methods are very popular, however, their documentation is empty (no javadoc at all), and it is not obvious if nulls are possible there or not.

> Clarify SqlCall#getOperandList() nullability
> --------------------------------------------
>
>                 Key: CALCITE-4219
>                 URL: https://issues.apache.org/jira/browse/CALCITE-4219
>             Project: Calcite
>          Issue Type: Sub-task
>          Components: core
>    Affects Versions: 1.25.0
>            Reporter: Vladimir Sitnikov
>            Priority: Major
>
> {{getOperandList()}} is implemented by a number of different {{SqlCall}} sub-classes, and the list often includes null values.
> The implementation is typically {{return ImmutableNullableList.of(...}}
> However, {{getOperandList()}} is used a lot, and the code assumes that the resulting values are non-null. The same happens for {{SqlCall#operand(int)}}.
> The workaround is to declare  {{getOperandList()}} and {{operand(int)}} to return non-nullable values (even though nulls are possible), and we could add suppressions at the side which returns {{ImmutableNullableList}}.
> The solution might be behind the lines of adding {{nonNullableOperand(int)}}-like methods that would return non-nullable values and throw meaningful errors in case the value turns out to be null.
> Another option might be to ensure all the fields are non-nullable (e.g. create dummy SqlNode for empty values).



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