[SPARK-33777][SQL] Sort output of V2 SHOW PARTITIONS

sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/v2/ShowPartitionsExec.scala

@@ -49,7 +49,7 @@ case class ShowPartitionsExec(
     val len = schema.length
     val partitions = new Array[String](len)
     val timeZoneId = SQLConf.get.sessionLocalTimeZone
-    partitionIdentifiers.map { row =>
+    val output = partitionIdentifiers.map { row =>
       var i = 0
       while (i < len) {
         val dataType = schema(i).dataType
@@ -59,7 +59,8 @@ case class ShowPartitionsExec(
         partitions(i) = escapePathName(schema(i).name) + "=" + escapePathName(partValueStr)
         i += 1
       }
-      InternalRow(UTF8String.fromString(partitions.mkString("/")))
+      partitions.mkString("/")
     }
+    output.sorted.map(p => InternalRow(UTF8String.fromString(p)))
   }
 }

sql/core/src/test/scala/org/apache/spark/sql/execution/command/ShowPartitionsSuiteBase.scala

@@ -173,4 +173,21 @@ trait ShowPartitionsSuiteBase extends QueryTest with SQLTestUtils {
       }
     }
   }
+
+  test("SPARK-33777: sorted output") {
+    withNamespace(s"$catalog.ns") {
+      sql(s"CREATE NAMESPACE $catalog.ns")
+      val table = s"$catalog.ns.dateTable"
+      withTable(table) {
+        sql(s"""
+          |CREATE TABLE $table (id int, part string)
+          |$defaultUsing
+          |PARTITIONED BY (part)""".stripMargin)
+        sql(s"ALTER TABLE $table ADD PARTITION(part = 'b')")
+        sql(s"ALTER TABLE $table ADD PARTITION(part = 'a')")
+        val partitions = sql(s"show partitions $table")
+        assert(partitions.first().getString(0) === "part=a")
+      }
+    }
+  }
 }