[fix](outfile)Preserve DateTimeV2 scale in OUTFILE CSV.

be/src/core/data_type_serde/data_type_datetimev2_serde.cpp

@@ -328,7 +328,7 @@ Status DataTypeDateTimeV2SerDe::serialize_one_cell_to_json(const IColumn& column
     auto val = assert_cast<const ColumnDateTimeV2&, TypeCheckOnRelease::DISABLE>(*ptr).get_element(
             row_num);
     char buf[64];
-    char* pos = val.to_string(buf);
+    char* pos = val.to_string(buf, _scale);
     bw.write(buf, pos - buf - 1);
 
     if (_nesting_level > 1) {

regression-test/suites/export_p0/test_outfile_datetimev2_scale.groovy

@@ -0,0 +1,110 @@
+// 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.
+
+import org.codehaus.groovy.runtime.IOGroovyMethods
+
+import java.nio.charset.StandardCharsets
+import java.nio.file.Files
+import java.nio.file.Paths
+
+suite("test_outfile_datetimev2_scale") {
+    StringBuilder strBuilder = new StringBuilder()
+    strBuilder.append("curl --location-trusted -u " + context.config.jdbcUser + ":" + context.config.jdbcPassword)
+    if ((context.config.otherConfigs.get("enableTLS")?.toString()?.equalsIgnoreCase("true")) ?: false) {
+        strBuilder.append(" https://" + context.config.feHttpAddress + "/rest/v1/config/fe")
+        strBuilder.append(" --cert " + context.config.otherConfigs.get("trustCert") + " --cacert " + context.config.otherConfigs.get("trustCACert") + " --key " + context.config.otherConfigs.get("trustCAKey"))
+    } else {
+        strBuilder.append(" http://" + context.config.feHttpAddress + "/rest/v1/config/fe")
+    }
+
+    String command = strBuilder.toString()
+    def process = command.execute()
+    def code = process.waitFor()
+    def err = IOGroovyMethods.getText(new BufferedReader(new InputStreamReader(process.getErrorStream())))
+    def out = process.getText()
+    logger.info("Request FE Config: code=" + code + ", out=" + out + ", err=" + err)
+    assertEquals(code, 0)
+    def response = parseJson(out.trim())
+    assertEquals(response.code, 0)
+    assertEquals(response.msg, "success")
+    def configJson = response.data.rows
+    boolean enableOutfileToLocal = false
+    for (Object conf: configJson) {
+        assert conf instanceof Map
+        if (((Map<String, String>) conf).get("Name").toLowerCase() == "enable_outfile_to_local") {
+            enableOutfileToLocal = ((Map<String, String>) conf).get("Value").toLowerCase() == "true"
+        }
+    }
+    if (!enableOutfileToLocal) {
+        logger.warn("Please set enable_outfile_to_local to true to run test_outfile_datetimev2_scale")
+        return
+    }
+
+    def tableName = "test_outfile_datetimev2_scale"
+    def uuid = UUID.randomUUID().toString()
+    def outFilePath = """/tmp/test_outfile_datetimev2_scale_${uuid}"""
+
+    try {
+        sql """ DROP TABLE IF EXISTS ${tableName} """
+        sql """
+            CREATE TABLE ${tableName} (
+                `id` INT,
+                `dt0` DATETIMEV2(0),
+                `dt3` DATETIMEV2(3),
+                `dt6` DATETIMEV2(6)
+            )
+            DUPLICATE KEY(`id`)
+            DISTRIBUTED BY HASH(`id`) BUCKETS 1
+            PROPERTIES("replication_num" = "1");
+        """
+        sql """
+            INSERT INTO ${tableName} VALUES
+            (1, '2026-06-06 15:54:51', '2026-06-06 15:54:51.442', '2026-06-06 15:54:51.442000');
+        """
+
+        File path = new File(outFilePath)
+        if (!path.exists()) {
+            assert path.mkdirs()
+        } else {
+            throw new IllegalStateException("""${outFilePath} already exists! """)
+        }
+
+        sql """
+            SELECT * FROM ${tableName} ORDER BY id
+            INTO OUTFILE "file://${outFilePath}/"
+            FORMAT AS CSV
+            PROPERTIES("column_separator" = ",");
+        """
+
+        File[] files = path.listFiles().findAll { it.isFile() && it.getName().endsWith(".csv") } as File[]
+        assertEquals(1, files.length)
+
+        List<String> outLines = Files.readAllLines(Paths.get(files[0].getAbsolutePath()), StandardCharsets.UTF_8)
+        assertEquals(1, outLines.size())
+        assertEquals("1,2026-06-06 15:54:51,2026-06-06 15:54:51.442,2026-06-06 15:54:51.442000", outLines.get(0))
+        assertFalse(outLines.get(0).contains("2026-06-06 15:54:51.442000,2026-06-06 15:54:51.442000"))
+    } finally {
+        try_sql("DROP TABLE IF EXISTS ${tableName}")
+        File path = new File(outFilePath)
+        if (path.exists()) {
+            for (File f: path.listFiles()) {
+                f.delete()
+            }
+            path.delete()
+        }
+    }
+}