Changeset values should honor comparators (#238)

* Alter change column behavior so that it honors comparators when determining what fields have changed

* Address requested changes

* Linter updates

src/main/scala/uk/co/gresearch/spark/diff/Diff.scala

@@ -19,6 +19,7 @@ package uk.co.gresearch.spark.diff
 import org.apache.spark.sql._
 import org.apache.spark.sql.functions._
 import org.apache.spark.sql.types.{ArrayType, StringType}
+import uk.co.gresearch.spark.diff.comparator.DiffComparator
 import uk.co.gresearch.spark.{backticks, distinctPrefixFor}
 
 import scala.collection.JavaConverters
@@ -144,20 +145,22 @@ class Differ(options: DiffOptions) {
 
   private def getChangeColumn(
       existsColumnName: String,
-      valueColumns: Seq[String],
+      valueVolumnsWithComparator: Seq[(String, DiffComparator)],
       left: Dataset[_],
       right: Dataset[_]
   ): Option[Column] = {
     options.changeColumn
       .map(changeColumn =>
         when(left(existsColumnName).isNull || right(existsColumnName).isNull, lit(null))
           .otherwise(
-            Some(valueColumns.toSeq)
+            Some(valueVolumnsWithComparator)
               .filter(_.nonEmpty)
               .map(columns =>
                 concat(
                   columns
-                    .map(c => when(left(backticks(c)) <=> right(backticks(c)), array()).otherwise(array(lit(c)))): _*
+                    .map { case (c, cmp) =>
+                      when(cmp.equiv(left(backticks(c)), right(backticks(c))), array()).otherwise(array(lit(c)))
+                    }: _*
                 )
               )
               .getOrElse(
@@ -282,6 +285,7 @@ class Differ(options: DiffOptions) {
         cmp.equiv(leftWithExists(backticks(c)), rightWithExists(backticks(c)))
       }
       .reduceOption(_ && _)
+
     val changeCondition = not(unChanged.getOrElse(lit(true)))
 
     val diffActionColumn =
@@ -292,7 +296,7 @@ class Differ(options: DiffOptions) {
         .as(options.diffColumn)
 
     val diffColumns = getDiffColumns(pkColumns, valueColumns, left, right, ignoreColumns).map(_._2)
-    val changeColumn = getChangeColumn(existsColumnName, valueColumns, leftWithExists, rightWithExists)
+    val changeColumn = getChangeColumn(existsColumnName, valueVolumnsWithComparator, leftWithExists, rightWithExists)
       // turn this column into a sequence of one or none column so we can easily concat it below with diffActionColumn and diffColumns
       .map(Seq(_))
       .getOrElse(Seq.empty[Column])

src/test/scala/uk/co/gresearch/spark/diff/DiffComparatorSuite.scala

@@ -33,6 +33,7 @@ import uk.co.gresearch.spark.diff.comparator._
 
 import java.sql.{Date, Timestamp}
 import java.time.Duration
+import java.util
 
 case class Numbers(
     id: Int,
@@ -412,6 +413,36 @@ class DiffComparatorSuite extends AnyFunSuite with SparkTestSession {
         DiffOptions.default.withComparator(DiffComparators.duration(Duration.ofSeconds(61)).asExclusive(), "time")
       doTest(optionsWithTightComparator, optionsWithRelaxedComparator, leftTimes.toDF, rightTimes.toDF)
     }
+
+    test("changeset accounts for comparators") {
+      val changesetOptions = DiffOptions.default
+        .withComparator(DiffComparators.epsilon(10).asAbsolute().asInclusive(), "longValue")
+        .withChangeColumn("changeset")
+
+      lazy val left: Dataset[Numbers] = Seq(
+        Numbers(1, 1L, 1.0f, 1.0, Decimal(10, 8, 3), None, None),
+        Numbers(2, 2L, 2.0f, 2.0, Decimal(20, 8, 3), Some(2), Some(2L)),
+        Numbers(3, 3L, 3.0f, 3.0, Decimal(30, 8, 3), Some(3), Some(3L)),
+        Numbers(4, 4L, 4.0f, 4.0, Decimal(40, 8, 3), Some(4), None),
+        Numbers(5, 5L, 5.0f, 5.0, Decimal(50, 8, 3), None, Some(5L)),
+      ).toDS()
+
+      lazy val right: Dataset[Numbers] = Seq(
+        Numbers(1, 1L, 1.0f, 1.0, Decimal(10, 8, 3), None, None),
+        Numbers(2, 8L, 2.0f, 2.0, Decimal(20, 8, 3), Some(2), Some(2L)),
+        Numbers(3, 9L, 6.0f, 3.0, Decimal(30, 8, 3), Some(3), Some(3L)),
+        Numbers(4, 10L, 4.0f, 4.0, Decimal(40, 8, 3), Some(4), None),
+        Numbers(5, 11L, 5.0f, 5.0, Decimal(50, 8, 3), None, Some(5L)),
+      ).toDS()
+
+      val rs = left.diff(right, changesetOptions, "id").where($"diff" === "C")
+      assert(rs.count() == 1, "Only one row should differ with the numeric comparator applied")
+      val changesInDifferingRow: util.List[String] = rs.head.getList[String](1)
+      assert(
+        changesInDifferingRow.get(0) == "floatValue",
+        "Only floatVal differs after considering the comparators so the changeset should be size 1"
+      )
+    }
   }
 
   Seq(true, false).foreach { sensitive =>