SPJ : fix bucket reducer function

minimized the test

remove order by

sql/core/src/test/scala/org/apache/spark/sql/connector/KeyGroupedPartitioningSuite.scala

@@ -1390,7 +1390,7 @@ class KeyGroupedPartitioningSuite extends DistributionAndOrderingSuiteBase {
     }
   }
 
-  test("SPARK-44647: test join key is subset of cluster key " +
+  test("SPARK-44647: SPJ: test join key is subset of cluster key " +
       "with push values and partially-clustered") {
     val table1 = "tab1e1"
     val table2 = "table2"
@@ -1487,7 +1487,7 @@ class KeyGroupedPartitioningSuite extends DistributionAndOrderingSuiteBase {
     }
   }
 
-  test("SPARK-47094: Support compatible buckets") {
+  test("SPARK-47094: SPJ: Support compatible buckets") {
     val table1 = "tab1e1"
     val table2 = "table2"
 
@@ -1580,11 +1580,11 @@ class KeyGroupedPartitioningSuite extends DistributionAndOrderingSuiteBase {
             val shuffles = collectShuffles(df.queryExecution.executedPlan)
             assert(shuffles.isEmpty, "SPJ should be triggered")
 
-            val scans = collectScans(df.queryExecution.executedPlan).map(_.inputRDD.
+            val partions = collectScans(df.queryExecution.executedPlan).map(_.inputRDD.
               partitions.length)
             val expectedBuckets = Math.min(table1buckets1, table2buckets1) *
               Math.min(table1buckets2, table2buckets2)
-            assert(scans == Seq(expectedBuckets, expectedBuckets))
+            assert(partions == Seq(expectedBuckets, expectedBuckets))
 
             checkAnswer(df, Seq(
               Row(0, 0, "aa", "aa"),
@@ -1647,7 +1647,7 @@ class KeyGroupedPartitioningSuite extends DistributionAndOrderingSuiteBase {
     }
   }
 
-  test("SPARK-47094: Support compatible buckets with common divisor") {
+  test("SPARK-47094: SPJ:Support compatible buckets with common divisor") {
     val table1 = "tab1e1"
     val table2 = "table2"
 
@@ -1744,9 +1744,9 @@ class KeyGroupedPartitioningSuite extends DistributionAndOrderingSuiteBase {
               partitions.length)
 
             def gcd(a: Int, b: Int): Int = BigInt(a).gcd(BigInt(b)).toInt
-            val expectedBuckets = gcd(table1buckets1, table2buckets1) *
+            val expectedPartitions = gcd(table1buckets1, table2buckets1) *
               gcd(table1buckets2, table2buckets2)
-            assert(scans == Seq(expectedBuckets, expectedBuckets))
+            assert(scans == Seq(expectedPartitions, expectedPartitions))
 
             checkAnswer(df, Seq(
               Row(0, 0, "aa", "aa"),
@@ -1809,6 +1809,56 @@ class KeyGroupedPartitioningSuite extends DistributionAndOrderingSuiteBase {
     }
   }
 
+
+  test("SPARK-47094: SPJ: Does not trigger when incompatible number of buckets on both side") {
+    val table1 = "tab1e1"
+    val table2 = "table2"
+
+    Seq(
+      (2, 3),
+      (3, 4)
+    ).foreach {
+      case (table1buckets1, table2buckets1) =>
+        catalog.clearTables()
+
+        val partition1 = Array(bucket(table1buckets1, "store_id"))
+        val partition2 = Array(bucket(table2buckets1, "store_id"))
+
+        Seq((table1, partition1), (table2, partition2)).foreach { case (tab, part) =>
+          createTable(tab, columns2, part)
+          val insertStr = s"INSERT INTO testcat.ns.$tab VALUES " +
+            "(0, 0, 'aa'), " +
+            "(1, 0, 'ab'), " + // duplicate partition key
+            "(2, 2, 'ac'), " +
+            "(3, 3, 'ad'), " +
+            "(4, 2, 'bc') "
+
+          sql(insertStr)
+        }
+
+        Seq(true, false).foreach { allowJoinKeysSubsetOfPartitionKeys =>
+          withSQLConf(
+            SQLConf.REQUIRE_ALL_CLUSTER_KEYS_FOR_CO_PARTITION.key -> "false",
+            SQLConf.V2_BUCKETING_PUSH_PART_VALUES_ENABLED.key -> "true",
+            SQLConf.V2_BUCKETING_PARTIALLY_CLUSTERED_DISTRIBUTION_ENABLED.key -> "false",
+            SQLConf.V2_BUCKETING_ALLOW_JOIN_KEYS_SUBSET_OF_PARTITION_KEYS.key ->
+              allowJoinKeysSubsetOfPartitionKeys.toString,
+            SQLConf.V2_BUCKETING_ALLOW_COMPATIBLE_TRANSFORMS.key -> "true") {
+            val df = sql(
+              s"""
+                 |${selectWithMergeJoinHint("t1", "t2")}
+                 |t1.store_id, t1.dept_id, t1.data, t2.data
+                 |FROM testcat.ns.$table1 t1 JOIN testcat.ns.$table2 t2
+                 |ON t1.store_id = t2.store_id AND t1.dept_id = t2.dept_id
+                 |""".stripMargin)
+
+            val shuffles = collectShuffles(df.queryExecution.executedPlan)
+            assert(shuffles.nonEmpty, "SPJ should not be triggered")
+          }
+        }
+    }
+  }
+
   test("SPARK-47094: Support compatible buckets with less join keys than partition keys") {
     val table1 = "tab1e1"
     val table2 = "table2"

sql/core/src/test/scala/org/apache/spark/sql/connector/catalog/functions/transformFunctions.scala

@@ -101,8 +101,8 @@ object BucketFunction extends ScalarFunction[Int] with ReducibleFunction[Int, In
 
     if (otherFunc == BucketFunction) {
       val gcd = this.gcd(thisNumBuckets, otherNumBuckets)
-      if (gcd != thisNumBuckets) {
-        return BucketReducer(thisNumBuckets, gcd)
+      if (gcd > 1 && gcd != thisNumBuckets) {
+        return BucketReducer(gcd)
       }
     }
     null
@@ -111,7 +111,7 @@ object BucketFunction extends ScalarFunction[Int] with ReducibleFunction[Int, In
   private def gcd(a: Int, b: Int): Int = BigInt(a).gcd(BigInt(b)).toInt
 }
 
-case class BucketReducer(thisNumBuckets: Int, divisor: Int) extends Reducer[Int, Int] {
+case class BucketReducer(divisor: Int) extends Reducer[Int, Int] {
   override def reduce(bucket: Int): Int = bucket % divisor
 }