cloud-fan commented on code in PR #39722:
URL: https://github.com/apache/spark/pull/39722#discussion_r1090479431
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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/arithmetic.scala:
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@@ -407,6 +408,74 @@ object BinaryArithmetic {
def unapply(e: BinaryArithmetic): Option[(Expression, Expression)] =
Some((e.left, e.right))
}
+/**
+ * A helper class used by the Add expression during canonicalization. During
+ * canonicalization, when we have a long tree of Add operations, we use the
MultiAdd expression
+ * to represent that tree instead of creating new Add objects. This class is
added as a memory
+ * optimization for processing large Add operation trees without creating a
large number of
+ * new intermediate objects.
+ * @param operands A sequence of operands that produces an Add tree.
+ * @param evalMode The expression evaluation mode.
+ */
+case class MultiAdd(operands: Seq[Expression], evalMode: EvalMode.Value)
extends Unevaluable {
+ // When `spark.sql.decimalOperations.allowPrecisionLoss` is set to true, if
the precision / scale
+ // needed are out of the range of available values, the scale is reduced up
to 6, in order to
+ // prevent the truncation of the integer part of the decimals.
+ private def allowPrecisionLoss: Boolean =
SQLConf.get.decimalOperationsAllowPrecisionLoss
+
+ // scalastyle:off
+ // The formula follows Hive which is based on the SQL standard and MS SQL:
+ //
https://cwiki.apache.org/confluence/download/attachments/27362075/Hive_Decimal_Precision_Scale_Support.pdf
+ // https://msdn.microsoft.com/en-us/library/ms190476.aspx
+ // Result Precision: max(s1, s2) + max(p1-s1, p2-s2) + 1
+ // Result Scale: max(s1, s2)
+ // scalastyle:on
+ private def resultDecimalType(p1: Int, s1: Int, p2: Int, s2: Int):
DecimalType = {
Review Comment:
shall we move it to a util function to avoid duplicating the code?
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