[GitHub] spark pull request #22494: [SPARK-22036][SQL][followup] add a new config for...

[mgaido91 <gi...@git.apache.org>]

Github user mgaido91 commented on a diff in the pull request:

    https://github.com/apache/spark/pull/22494#discussion_r219492191
  
    --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala ---
    @@ -1345,6 +1345,16 @@ object SQLConf {
           .booleanConf
           .createWithDefault(true)
     
    +  val LITERAL_PRECISE_PRECISION =
    +    buildConf("spark.sql.literal.precisePrecision")
    +      .internal()
    +      .doc("When integral literals are used with decimals in binary operators, Spark will " +
    +        "pick a precise precision for the literals to calculate the precision and scale " +
    +        "of the result decimal, when this config is true. By picking a precise precision, we " +
    +        "can avoid wasting precision, to reduce the possibility of overflow.")
    --- End diff --
    
    `to reduce the possibility of overflow` actually this is not true and depends on the value of `DECIMAL_OPERATIONS_ALLOW_PREC_LOSS`, If `DECIMAL_OPERATIONS_ALLOW_PREC_LOSS` is true, the risk is to have a precision loss, but we don't overflow. If that is false, then this statement is right.


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