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https://issues.apache.org/jira/browse/CALCITE-5607?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17719015#comment-17719015
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Julian Hyde commented on CALCITE-5607:
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The return type of a {{RexCall}} should be derivable from its arguments. That
principle has served us well for a long time, so we shouldn't abandon it
lightly.
I see your point that the return type of {{MINUS_DATE}} can't be derived from
two arguments. It reminds me of {{CAST}} (which has two arguments in
{{SqlNode}} form, but only one argument in {{RexNode}} form). Can you
investigate how {{RelJson}} deals with {{CAST}}? There's probably a Jira case.
> Serialize return type during RelJson.toJson(RexNode node) serialization
> ------------------------------------------------------------------------
>
> Key: CALCITE-5607
> URL: https://issues.apache.org/jira/browse/CALCITE-5607
> Project: Calcite
> Issue Type: Improvement
> Reporter: Oliver Lee
> Assignee: Oliver Lee
> Priority: Major
> Labels: pull-request-available
> Time Spent: 1h 10m
> Remaining Estimate: 0h
>
> We found a bug in {{RelJson#toRex}} for the {{TIMESTAMP_DIFF}} call for Big
> Query dialect.
> {{TIMESTAMP_DIFF}} is translated to the {{MINUS_DATE}}
> [operator|https://github.com/apache/calcite/blob/c28d1dcbc34e748b7bea9712ef6bcf43793a91e8/core/src/main/java/org/apache/calcite/sql2rel/StandardConvertletTable.java#L2113-L2116]
> with a return type explicitly declared as the interval.
> {{MINUS_DATE}} uses an
> {{[ARG2_NULLABLE|https://github.com/apache/calcite/blob/c28d1dcbc34e748b7bea9712ef6bcf43793a91e8/core/src/main/java/org/apache/calcite/sql/type/ReturnTypes.java#L241]}}
> return type inference which requires 3 operands. This is fine in most cases
> where the RexCall is then used to generate SQL or for native implementations.
> However, in {{{}RelJson#toRex{}}}, when it tries to reconstruct the entire
> call to a RexNode, it attempts to derive the return type of the
> {{MINUS_DATE}} operator using the {{ARG2_NULLABLE}} inference. This throws an
> error as there are only 2 operands given to the {{MINUS_DATE}} operator.
> We'd like to now add in the "type" when serializing the JSON so that
> {{[jsonType|https://github.com/apache/calcite/blob/c28d1dcbc34e748b7bea9712ef6bcf43793a91e8/core/src/main/java/org/apache/calcite/rel/externalize/RelJson.java#L712]}}
> will be defined in {{{}toRex{}}}.
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