[spark] Fix ArrayIndexOutOfBoundsException reading empty partitioned format table

paimon-spark/paimon-spark-common/src/main/scala/org/apache/spark/sql/execution/SparkFormatTable.scala

@@ -92,14 +92,29 @@ object SparkFormatTable {
     }
   }
 
+  private def alignPartitionSpec(
+      inferred: PartitionSpec,
+      partitionSchema: StructType): PartitionSpec = {
+    if (inferred.partitionColumns.isEmpty && partitionSchema.nonEmpty) {
+      PartitionSpec(partitionSchema, inferred.partitions)
+    } else {
+      inferred
+    }
+  }
+
   // Extend from MetadataLogFileIndex to override partitionSchema
   private class PartitionedMetadataLogFileIndex(
       sparkSession: SparkSession,
       path: Path,
       parameters: Map[String, String],
       userSpecifiedSchema: Option[StructType],
       override val partitionSchema: StructType)
-    extends MetadataLogFileIndex(sparkSession, path, parameters, userSpecifiedSchema)
+    extends MetadataLogFileIndex(sparkSession, path, parameters, userSpecifiedSchema) {
+
+    override def partitionSpec(): PartitionSpec = {
+      alignPartitionSpec(super.partitionSpec(), partitionSchema)
+    }
+  }
 
   // Extend from InMemoryFileIndex to override partitionSchema
   private class PartitionedInMemoryFileIndex(
@@ -118,7 +133,12 @@ object SparkFormatTable {
       userSpecifiedSchema,
       fileStatusCache,
       userSpecifiedPartitionSpec,
-      metadataOpsTimeNs)
+      metadataOpsTimeNs) {
+
+    override def partitionSpec(): PartitionSpec = {
+      alignPartitionSpec(super.partitionSpec(), partitionSchema)
+    }
+  }
 }
 
 trait PartitionedFormatTable extends SupportsPartitionManagement {

paimon-spark/paimon-spark-ut/src/test/scala/org/apache/paimon/spark/table/PaimonFormatTableTest.scala

@@ -405,6 +405,27 @@ class PaimonFormatTableTest extends PaimonSparkTestWithRestCatalogBase {
     }
   }
 
+  test(
+    "PartitionedFormatTable: engine impl should return empty result when selecting a partition column on an empty table") {
+    val tableName = "engine_empty_partition_select"
+    withTable(tableName) {
+      val location = s"${tempDBDir.getCanonicalPath}/engine_empty_partition_select"
+      sql(s"""CREATE TABLE $tableName (clickid STRING, geo STRING, dt STRING, hour STRING)
+             |USING parquet PARTITIONED BY (dt, hour) LOCATION '$location'
+             |TBLPROPERTIES ('format-table.implementation'='engine')
+             |""".stripMargin)
+      fileIO.mkdirs(new Path(location))
+      checkAnswer(sql(s"SELECT clickid, hour FROM $tableName WHERE dt='20260418'"), Nil)
+      checkAnswer(sql(s"SELECT clickid, dt FROM $tableName WHERE hour='00'"), Nil)
+      checkAnswer(
+        sql(s"""SELECT clickid, max(hour) AS max_hour FROM $tableName
+               |WHERE dt='20260418' AND hour <= '11' AND geo IS NOT NULL
+               |GROUP BY clickid""".stripMargin),
+        Nil
+      )
+    }
+  }
+
   test("Paimon format table: show partitions") {
     withTable("t") {
       sql("""