[bugfix](iceberg)clear block for partition values (apache#39569)

## Proposed changes

clear block, or we will get wrong partition values.

be/src/vec/sink/writer/iceberg/viceberg_table_writer.cpp

@@ -163,6 +163,7 @@ Status VIcebergTableWriter::write(RuntimeState* state, vectorized::Block& block)
 
     {
         SCOPED_RAW_TIMER(&_partition_writers_dispatch_ns);
+        _transformed_block.clear();
         _transformed_block.reserve(_iceberg_partition_columns.size());
         for (auto& iceberg_partition_columns : _iceberg_partition_columns) {
             _transformed_block.insert(iceberg_partition_columns.partition_column_transform().apply(

regression-test/data/external_table_p0/iceberg/write/test_iceberg_overwrite_with_wrong_partition.out

@@ -0,0 +1,23 @@
+-- This file is automatically generated. You should know what you did if you want to edit this
+-- !qt01 --
+2450841	2450841
+2450841	2450841
+2450842	2450842
+2450842	2450842
+2450843	2450843
+2450843	2450843
+2450844	2450844
+2450844	2450844
+2450845	2450845
+2450845	2450845
+2450846	2450846
+2450846	2450846
+2450847	2450847
+2450847	2450847
+2450848	2450848
+2450848	2450848
+2450849	2450849
+2450849	2450849
+2450850	2450850
+2450850	2450850
+

regression-test/suites/external_table_p0/iceberg/write/test_iceberg_overwrite_with_wrong_partition.groovy

@@ -0,0 +1,84 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+suite("test_iceberg_overwrite_with_wrong_partition", "p0,external,doris,external_docker,external_docker_doris") {
+    String enabled = context.config.otherConfigs.get("enableIcebergTest")
+    if (enabled == null || !enabled.equalsIgnoreCase("true")) {
+        logger.info("disable iceberg test.")
+        return
+    }
+
+    String tb1 = "tb_dst";
+    String tb2 = "tb_src";
+
+    try {
+        String rest_port = context.config.otherConfigs.get("iceberg_rest_uri_port")
+        String minio_port = context.config.otherConfigs.get("iceberg_minio_port")
+        String externalEnvIp = context.config.otherConfigs.get("externalEnvIp")
+        String catalog_name = "test_iceberg_overwrite_with_wrong_partition"
+
+        sql """drop catalog if exists ${catalog_name}"""
+        sql """CREATE CATALOG ${catalog_name} PROPERTIES (
+                'type'='iceberg',
+                'iceberg.catalog.type'='rest',
+                'uri' = 'http://${externalEnvIp}:${rest_port}',
+                "s3.access_key" = "admin",
+                "s3.secret_key" = "password",
+                "s3.endpoint" = "http://${externalEnvIp}:${minio_port}",
+                "s3.region" = "us-east-1"
+            );"""
+
+        sql """ switch ${catalog_name} """
+        sql """ use multi_catalog """
+
+        sql """ drop table if exists ${tb1} """
+        sql """ drop table if exists ${tb2} """
+
+        sql """ 
+        create table ${tb1} (
+            id bigint,
+            id2 bigint
+        ) PARTITION BY LIST(id2)() ;
+        """
+        sql """ 
+        create table ${tb2} (
+            id bigint,
+            id2 bigint
+        );
+        """
+
+        sql """ insert into ${tb2} values (2450841,2450841), (2450842,2450842); """
+        sql """ insert into ${tb2} values (2450843,2450843), (2450844,2450844); """
+        sql """ insert into ${tb2} values (2450845,2450845), (2450846,2450846); """
+        sql """ insert into ${tb2} values (2450847,2450847), (2450848,2450848); """
+        sql """ insert into ${tb2} values (2450849,2450849), (2450850,2450850); """
+        sql """ insert into ${tb2} values (2450841,2450841), (2450842,2450842); """
+        sql """ insert into ${tb2} values (2450843,2450843), (2450844,2450844); """
+        sql """ insert into ${tb2} values (2450845,2450845), (2450846,2450846); """
+        sql """ insert into ${tb2} values (2450847,2450847), (2450848,2450848); """
+        sql """ insert into ${tb2} values (2450849,2450849), (2450850,2450850); """
+
+        sql """ insert overwrite table ${tb1} (id, id2) select id, id2 from ${tb2} where id2 >= 2450841 AND id2 < 2450851; """
+
+        order_qt_qt01 """ select * from ${tb1} """
+
+    } finally {
+        sql """ drop table if exists ${tb1} """
+        sql """ drop table if exists ${tb2} """
+    }
+}
+