[fix](Tvf) return empty set when tvf queries an empty file or an error uri

docs/en/docs/lakehouse/file.md

@@ -193,3 +193,9 @@ FROM s3(
     "use_path_style" = "true");
 ```
 
+
+### Note
+
+1. If the URI specified by the `S3 / HDFS` TVF is not matched with the file, or all the matched files are empty files, then the` S3 / HDFS` TVF will return to the empty result set. In this case, using the `DESC FUNCTION` to view the schema of this file, you will get a dummy column` __dummy_col`, which can be ignored.
+
+2. If the format of the TVF is specified to `CSV`, and the read file is not a empty file but the first line of this file is empty, then it will prompt the error `The first line is empty, can not parse column numbers`. This is because the schema cannot be parsed from the first line of the file

docs/en/docs/sql-manual/sql-functions/table-functions/hdfs.md

@@ -51,7 +51,7 @@ hdfs(
 
 Related parameters for accessing hdfs:
 
-- `uri`: (required) hdfs uri.
+- `uri`: (required) hdfs uri. If the uri path does not exist or the files are empty files, hdfs tvf will return an empty result set.
 - `fs.defaultFS`: (required)
 - `hadoop.username`: (required) Can be any string, but cannot be empty.
 - `hadoop.security.authentication`: (optional)

docs/en/docs/sql-manual/sql-functions/table-functions/s3.md

@@ -63,6 +63,7 @@ Related parameters for accessing S3:
 > Note: URI currently supports three SCHEMA: http://, https:// and s3://.
 > 1. If you use http:// or https://, you will decide whether to use the 'path style' to access s3 based on the 'use_path_style' parameter
 > 2. If you use s3://, you will use the "virtual-hosted style' to access the s3, 'use_path_style' parameter is invalid.
+> 3. If the uri path does not exist or the files are empty files, s3 tvf will return an empty result set.
 >
 > For detailed use cases, you can refer to Best Practice at the bottom.
 

docs/zh-CN/docs/lakehouse/file.md

@@ -193,3 +193,9 @@ FROM s3(
     "use_path_style" = "true");
 ```    
 
+### 注意事项
+
+1. 如果 `S3 / hdfs` tvf指定的uri匹配不到文件，或者匹配到的所有文件都是空文件，那么 `S3 / hdfs` tvf将会返回空结果集。在这种情况下使用`DESC FUNCTION`查看这个文件的Schema，会得到一列虚假的列`__dummy_col`，可忽略这一列。
+
+2. 如果指定tvf的format为csv，所读文件不为空文件但文件第一行为空，则会提示错误`The first line is empty, can not parse column numbers`, 这因为无法通过该文件的第一行解析出schema。
+

docs/zh-CN/docs/sql-manual/sql-functions/table-functions/hdfs.md

@@ -53,7 +53,7 @@ hdfs(
 **参数说明**
 
 访问hdfs相关参数：
-- `uri`：（必填） 访问hdfs的uri。
+- `uri`：（必填） 访问hdfs的uri。如果uri路径不存在或文件都是空文件，hdfs tvf将返回空集合。
 - `fs.defaultFS`：（必填）
 - `hadoop.username`： （必填）可以是任意字符串，但不能为空
 - `hadoop.security.authentication`：（选填）

docs/zh-CN/docs/sql-manual/sql-functions/table-functions/s3.md

@@ -66,6 +66,7 @@ S3 tvf中的每一个参数都是一个 `"key"="value"` 对。
 > 注意：uri目前支持三种schema：http://, https:// 和 s3://
 > 1. 如果使用http://或https://, 则会根据 'use_path_style' 参数来决定是否使用'path style'方式访问s3
 > 2. 如果使用s3://, 则都使用 'virtual-hosted style' 方式访问s3, 'use_path_style'参数无效。
+> 3. 如果uri路径不存在或文件都是空文件，s3 tvf将返回空集合
 >
 > 详细使用案例可以参考最下方 Best Practice。
 

fe/fe-core/src/main/java/org/apache/doris/tablefunction/ExternalFileTableValuedFunction.java

@@ -344,22 +344,27 @@ public List<Column> getTableColumns() throws AnalysisException {
         TNetworkAddress address = new TNetworkAddress(be.getHost(), be.getBrpcPort());
         try {
             PFetchTableSchemaRequest request = getFetchTableStructureRequest();
-            Future<InternalService.PFetchTableSchemaResult> future = BackendServiceProxy.getInstance()
-                    .fetchTableStructureAsync(address, request);
-
-            InternalService.PFetchTableSchemaResult result = future.get();
-            TStatusCode code = TStatusCode.findByValue(result.getStatus().getStatusCode());
-            String errMsg;
-            if (code != TStatusCode.OK) {
-                if (!result.getStatus().getErrorMsgsList().isEmpty()) {
-                    errMsg = result.getStatus().getErrorMsgsList().get(0);
-                } else {
-                    errMsg = "fetchTableStructureAsync failed. backend address: "
-                            + address.getHostname() + ":" + address.getPort();
+            InternalService.PFetchTableSchemaResult result = null;
+
+            // `request == null` means we don't need to get schemas from BE,
+            // and we fill a dummy col for this table.
+            if (request != null) {
+                Future<InternalService.PFetchTableSchemaResult> future = BackendServiceProxy.getInstance()
+                        .fetchTableStructureAsync(address, request);
+
+                result = future.get();
+                TStatusCode code = TStatusCode.findByValue(result.getStatus().getStatusCode());
+                String errMsg;
+                if (code != TStatusCode.OK) {
+                    if (!result.getStatus().getErrorMsgsList().isEmpty()) {
+                        errMsg = result.getStatus().getErrorMsgsList().get(0);
+                    } else {
+                        errMsg = "fetchTableStructureAsync failed. backend address: "
+                                + address.getHostname() + ":" + address.getPort();
+                    }
+                    throw new AnalysisException(errMsg);
                 }
-                throw new AnalysisException(errMsg);
             }
-
             fillColumns(result);
         } catch (RpcException e) {
             throw new AnalysisException("fetchTableStructureResult rpc exception", e);
@@ -431,10 +436,12 @@ private Pair<Type, Integer> getColumnType(List<PTypeNode> typeNodes, int start)
         return Pair.of(type, parsedNodes);
     }
 
-    private void fillColumns(InternalService.PFetchTableSchemaResult result)
-            throws AnalysisException {
-        if (result.getColumnNums() == 0) {
-            throw new AnalysisException("The amount of column is 0");
+    private void fillColumns(InternalService.PFetchTableSchemaResult result) {
+        // `result == null` means we don't need to get schemas from BE,
+        // and we fill a dummy col for this table.
+        if (result == null) {
+            columns.add(new Column("__dummy_col", ScalarType.createStringType(), true));
+            return;
         }
         // add fetched file columns
         for (int idx = 0; idx < result.getColumnNums(); ++idx) {
@@ -450,7 +457,7 @@ private void fillColumns(InternalService.PFetchTableSchemaResult result)
         }
     }
 
-    private PFetchTableSchemaRequest getFetchTableStructureRequest() throws AnalysisException, TException {
+    private PFetchTableSchemaRequest getFetchTableStructureRequest() throws TException {
         // set TFileScanRangeParams
         TFileScanRangeParams fileScanRangeParams = new TFileScanRangeParams();
         fileScanRangeParams.setFormatType(fileFormatType);
@@ -475,14 +482,19 @@ private PFetchTableSchemaRequest getFetchTableStructureRequest() throws Analysis
         // get first file, used to parse table schema
         TBrokerFileStatus firstFile = null;
         for (TBrokerFileStatus fileStatus : fileStatuses) {
-            if (fileStatus.isIsDir()) {
+            if (fileStatus.isIsDir() || fileStatus.size == 0) {
                 continue;
             }
             firstFile = fileStatus;
             break;
         }
+
+        // `firstFile == null` means:
+        // 1. No matching file path exists
+        // 2. All matched files have a size of 0
+        // For these two situations, we don't need to get schema from BE
         if (firstFile == null) {
-            throw new AnalysisException("Can not get first file, please check uri.");
+            return null;
         }
 
         // set TFileRangeDesc

regression-test/data/external_table_p0/tvf/test_hdfs_tvf_error_uri.out

@@ -0,0 +1,6 @@
+-- This file is automatically generated. You should know what you did if you want to edit this
+-- !select1 --
+
+-- !desc1 --
+__dummy_col	TEXT	Yes	false	\N	NONE
+

regression-test/data/load_p0/tvf/test_tvf_empty_file.out

@@ -0,0 +1,17 @@
+-- This file is automatically generated. You should know what you did if you want to edit this
+-- !select --
+
+-- !desc --
+__dummy_col	TEXT	Yes	false	\N	NONE
+
+-- !select2 --
+1	doris	18
+2	nereids	20
+3	xxx	22
+4	yyy	21
+
+-- !des2 --
+c1	TEXT	Yes	false	\N	NONE
+c2	TEXT	Yes	false	\N	NONE
+c3	TEXT	Yes	false	\N	NONE
+

regression-test/data/load_p0/tvf/test_tvf_error_url.out

@@ -0,0 +1,11 @@
+-- This file is automatically generated. You should know what you did if you want to edit this
+-- !select --
+
+-- !desc --
+__dummy_col	TEXT	Yes	false	\N	NONE
+
+-- !select2 --
+
+-- !desc2 --
+__dummy_col	TEXT	Yes	false	\N	NONE
+

regression-test/suites/external_table_p0/tvf/test_hdfs_tvf_error_uri.groovy

@@ -0,0 +1,43 @@
+// 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_hdfs_tvf_error_uri","external,hive,tvf,external_docker") {
+    String hdfs_port = context.config.otherConfigs.get("hdfs_port")
+    String externalEnvIp = context.config.otherConfigs.get("externalEnvIp")
+
+    // It's okay to use random `hdfsUser`, but can not be empty.
+    def hdfsUserName = "doris"
+    def format = "csv"
+    def defaultFS = "hdfs://${externalEnvIp}:${hdfs_port}"
+    def uri = ""
+
+    String enabled = context.config.otherConfigs.get("enableHiveTest")
+    if (enabled != null && enabled.equalsIgnoreCase("true")) {
+        // test csv format
+        uri = "${defaultFS}" + "/user/doris/preinstalled_data/csv_format_test/no_exist_file.csv"
+        format = "csv"
+        order_qt_select1 """ select * from HDFS(
+                    "uri" = "${uri}",
+                    "hadoop.username" = "${hdfsUserName}",
+                    "format" = "${format}"); """
+
+        order_qt_desc1 """ desc function HDFS(
+                    "uri" = "${uri}",
+                    "hadoop.username" = "${hdfsUserName}",
+                    "format" = "${format}"); """
+    }
+}

regression-test/suites/load_p0/tvf/test_tvf_empty_file.groovy

@@ -0,0 +1,69 @@
+// 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_tvf_empty_file", "p0") {
+       String ak = getS3AK()
+       String sk = getS3SK()
+       String s3_endpoint = getS3Endpoint()
+       String region = getS3Region()
+       String bucket = context.config.otherConfigs.get("s3BucketName");
+
+       String path = "regression/datalake"
+
+       // ${path}/empty_file_test.csv is an empty file
+       // so it should return empty sets.
+       order_qt_select """ SELECT * FROM S3 (
+                                   "uri" = "http://${bucket}.${s3_endpoint}/${path}/empty_file_test.csv",
+                                   "ACCESS_KEY"= "${ak}",
+                                   "SECRET_KEY" = "${sk}",
+                                   "format" = "csv",
+                                   "region" = "${region}"
+                                   );
+                            """
+
+       order_qt_desc """ desc function S3 (
+                                   "uri" = "http://${bucket}.${s3_endpoint}/${path}/empty_file_test.csv",
+                                   "ACCESS_KEY"= "${ak}",
+                                   "SECRET_KEY" = "${sk}",
+                                   "format" = "csv",
+                                   "region" = "${region}"
+                                   );
+                            """
+
+       // ${path}/empty_file_test*.csv matches 3 files:
+       // empty_file_test.csv, empty_file_test_1.csv, empty_file_test_2.csv
+       // empty_file_test.csv is an empty file, but
+       // empty_file_test_1.csv and empty_file_test_2.csv have data
+       // so it should return data of empty_file_test_1.csv and empty_file_test_2.cs
+       order_qt_select2 """ SELECT * FROM S3 (
+                                   "uri" = "http://${bucket}.${s3_endpoint}/${path}/empty_file_test*.csv",
+                                   "ACCESS_KEY"= "${ak}",
+                                   "SECRET_KEY" = "${sk}",
+                                   "format" = "csv",
+                                   "region" = "${region}"
+                                   ) order by c1;
+                            """
+
+       order_qt_des2 """ desc function S3 (
+                                   "uri" = "http://${bucket}.${s3_endpoint}/${path}/empty_file_test*.csv",
+                                   "ACCESS_KEY"= "${ak}",
+                                   "SECRET_KEY" = "${sk}",
+                                   "format" = "csv",
+                                   "region" = "${region}"
+                                   );
+                            """
+}

regression-test/suites/load_p0/tvf/test_tvf_error_url.groovy

@@ -0,0 +1,61 @@
+// 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_tvf_error_url", "p0") {
+    String ak = getS3AK()
+    String sk = getS3SK()
+    String s3_endpoint = getS3Endpoint()
+    String region = getS3Region()
+    String bucket = context.config.otherConfigs.get("s3BucketName");
+
+    String path = "select_tvf/no_exists_file_test"
+    order_qt_select """ SELECT * FROM S3 (
+                            "uri" = "http://${s3_endpoint}/${bucket}/${path}/no_exist_file1.csv",
+                            "ACCESS_KEY"= "${ak}",
+                            "SECRET_KEY" = "${sk}",
+                            "format" = "csv",
+                            "region" = "${region}"
+                            );
+                     """
+
+    order_qt_desc """ desc function S3 (
+                            "uri" = "http://${s3_endpoint}/${bucket}/${path}/no_exist_file1.csv",
+                            "ACCESS_KEY"= "${ak}",
+                            "SECRET_KEY" = "${sk}",
+                            "format" = "csv",
+                            "region" = "${region}"
+                            );
+                     """
+
+    order_qt_select2 """ SELECT * FROM S3 (
+                            "uri" = "http://${s3_endpoint}/${bucket}/${path}/*.csv",
+                            "ACCESS_KEY"= "${ak}",
+                            "SECRET_KEY" = "${sk}",
+                            "format" = "csv",
+                            "region" = "${region}"
+                            );
+                     """
+
+    order_qt_desc2 """ desc function S3 (
+                            "uri" = "http://${s3_endpoint}/${bucket}/${path}/*.csv",
+                            "ACCESS_KEY"= "${ak}",
+                            "SECRET_KEY" = "${sk}",
+                            "format" = "csv",
+                            "region" = "${region}"
+                            );
+                     """
+}