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https://issues.apache.org/jira/browse/SPARK-27768?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16844374#comment-16844374
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Xiao Li commented on SPARK-27768:
---------------------------------

Both DB2 and PostgreSQL treat 'infinity' like special values case insensitive. 
In the past, Hive compatibility is important to us. Now, when more and more 
traditional database users start migrating the workloads to Spark, we should 
also improve the compatibility and simplify the migration. 

This is especially true for the type coercion rules. The type coercion rules in 
Hive have various issues based on the JIRAs reported by our Spark users. I 
think we need to consider and introduce a new set of type coercion rules by 
following the true ANSI-compliant SQL systems like postgreSQL.

> Infinity, -Infinity, NaN should be recognized in a case insensitive manner
> --------------------------------------------------------------------------
>
>                 Key: SPARK-27768
>                 URL: https://issues.apache.org/jira/browse/SPARK-27768
>             Project: Spark
>          Issue Type: Sub-task
>          Components: SQL
>    Affects Versions: 3.0.0
>            Reporter: Xiao Li
>            Priority: Major
>
> When the inputs contain the constant 'infinity', Spark SQL does not generate 
> the expected results.
> {code:java}
> SELECT avg(CAST(x AS DOUBLE)), var_pop(CAST(x AS DOUBLE))
> FROM (VALUES ('1'), (CAST('infinity' AS DOUBLE))) v(x);
> SELECT avg(CAST(x AS DOUBLE)), var_pop(CAST(x AS DOUBLE))
> FROM (VALUES ('infinity'), ('1')) v(x);
> SELECT avg(CAST(x AS DOUBLE)), var_pop(CAST(x AS DOUBLE))
> FROM (VALUES ('infinity'), ('infinity')) v(x);
> SELECT avg(CAST(x AS DOUBLE)), var_pop(CAST(x AS DOUBLE))
> FROM (VALUES ('-infinity'), ('infinity')) v(x);{code}
>  The root cause: Spark SQL does not recognize the special constants in a case 
> insensitive way. In PostgreSQL, they are recognized in a case insensitive 
> way. 
> Link: https://www.postgresql.org/docs/9.3/datatype-numeric.html 
>  



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