Exporting data from HDFS to OBS

The data export function can export data in specified tables or partitions to remote storage devices in text format through the Broker process, such as HDFS and object storage (supporting the S3 protocol).

You are not advised to export a large amount of data at a time. It is recommended that a maximum of dozens of GB data be exported for an export job. Large exports result in more junk files and higher retry costs.
If the table contains a large amount of data, you are advised to export the data by partition.
If the FE is restarted or an active/standby switchover occurs during the running of the Export job, the Export job fails and you need to submit the job again.
If the export job fails, the temporary directory __doris_export_tmp_xxx generated in the remote storage and the generated files will not be deleted. You need to manually delete them.
If the export job is successfully executed, the __doris_export_tmp_xxx directory generated in the remote storage may be retained or cleared based on the file system semantics of the remote storage.
For example, in object storage (supporting the S3 protocol), after the last file in a directory is moved through the rename operation, the directory is also deleted. If the directory is not cleared, you can manually clear it.
After the export is complete (successful or failed), if the FE is restarted or an active/standby switchover occurs, some job information displayed in SHOW EXPORT will be lost and cannot be viewed.
The Export job exports only Base table data and does not export Rollup Index data.
The Export job scans data and occupies I/O resources, which may affect the query delay of the system.

Syntax

Exporting Doris Data to HDFS

Kerberos authentication is enabled for the cluster (the cluster is in security mode)
EXPORT TABLE db1.tbl1

PARTITION (p1,p2)

[WHERE [expr]]

TO "hdfs://IP address of the active NameNode instance:RPC port number/tmp/export/"

PROPERTIES

(

"label" = "mylabel",

"column_separator"=",",

"columns" = "col1,col2",

"exec_mem_limit"="2147483648",

"timeout" = "3600"

)

WITH BROKER "broker_name"

(

"hadoop.security.authentication"="kerberos",

"kerberos_principal"="doris/hadoop.hadoop.com@HADOOP.COM",

"kerberos_keytab"="${BIGDATA_HOME}/FusionInsight_Doris_*/install/FusionInsight-Doris-*/doris-fe/bin/doris.keytab"

);
Kerberos authentication is disabled for the cluster (the cluster is in normal mode)
EXPORT TABLE db1.tbl1

PARTITION (p1,p2)

[WHERE [expr]]

TO "hdfs://IP address of the active NameNode instance:RPC port number/tmp/export/"

PROPERTIES

(

"label" = "mylabel",

"column_separator"=",",

"columns" = "col1,col2",

"exec_mem_limit"="2147483648",

"timeout" = "3600"

)

WITH BROKER "broker_name"

(

"username" = "user",

"password" = "passwd"

);

To view the IP address of the active NameNode instance, log in to FusionInsight Manager and choose Cluster > Services > HDFS > Instances.

You can log in to FusionInsight Manager, choose Cluster > Services > HDFS > Configurations, and search for dfs.namenode.rpc.port to view the RPC port.

Table 1 describes other parameters.

**Table 1** Parameters in the command for exporting Doris data to HDFS
Parameter	Description
label	URN of the export job. You can use this identifier to view the job status.
column_separator	Column separator. The default value is \t. Invisible characters are supported, for example, '\x07'.
columns	Columns to be exported. Use commas (,) to separate them. If this parameter is not set, all columns in the table are exported by default.
line_delimiter	Line separator. The default value is \n. Invisible characters are supported, for example, '\x07'.
exec_mem_limit	Memory usage limit of a query plan on a BE in an export job. The default value is 2 GB, in bytes.
timeout	Job timeout interval. The default value is 2 hours. The unit is second.
tablet_num_per_task	Maximum number of shards allocated to each query plan. The default value is 5.

Viewing the Status of an Export Job

After submitting a job, you can run the SHOW EXPORT; command to query the status of the export job. For example:

JobId: 14008
State: FINISHED
Progress: 100%
TaskInfo: {"partitions":["*"],"exec mem limit":2147483648,"column separator":",","line delimiter":"\n","tablet num":1,"broker":"hdfs","coord num":1,"db":"default_cluster:db1","tbl":"tbl3"}
Path: hdfs://host/path/to/export/
CreateTime: 2019-06-25 17:08:24
StartTime: 2019-06-25 17:08:28
FinishTime: 2019-06-25 17:08:34
Timeout: 3600
ErrorMsg: NULL
1 row in set (0.01 sec)

The following table describes the parameters.

**Table 2** Parameters for exporting job status
Parameter	Description
JobId	Job ID, which is unique.
State	Job status. The options are as follows: PENDING: The job is to be scheduled. EXPORTING: Data is being exported. FINISHED: The job is successfully exported. ANCELLED: The export job fails to be executed.
Progress	Job progress, in the unit of query plan. Assume that there are 10 query plans in total and three of them have been completed. The progress is 30%.
TaskInfo	Job information displayed in JSON format, where: db: database name. tbl: table name partitions: specifies the partition to be exported. * indicates all partitions. exec mem limit: queries the memory usage limit of the plan. in byte. column separator: column separator of the exported file. line delimiter: line delimiter of the exported file. tablet num: total number of tablets. broker: name of the used broker. coord num: number of query plans.
Path	Export path on the remote storage device.
CreateTime/StartTime/FinishTime:	Creation time, scheduling start time, and end time of a job.
Timeout	Job timeout interval, in seconds. The time starts from CreateTime.
ErrorMsg	If an error occurs in the job, ErrorMsg displays the cause of the error.

Canceling an Export Task
After submitting a job, you can run the CANCEL_EXPORT command to cancel the export job. The cancellation command is as follows:

CANCEL EXPORT

FROM example_db

WHERE LABEL like "%example%";

Prerequisite

A cluster containing the Doris service has been created, and all services in the cluster are running properly.
The node to be connected to the Doris database can communicate with the MRS cluster.
A user with Doris management permission has been created.
- Kerberos authentication is enabled for the cluster (the cluster is in security mode)
  Log in to FusionInsight Manager, create a human-machine user, for example, dorisuser, create a role with Doris administrator permissions, and bind the role to the user.
  
  Log in to FusionInsight Manager as the created dorisuser user, and change the initial password.
- Kerberos authentication is disabled for the cluster (the cluster is in normal mode)
  After connecting to Doris as user admin, create a role with administrator permissions, and bind the role to the user.
The MySQL client has been installed. For details, see Installing a MySQL Client.

Example of Exporting a Job

Log in to the node where MySQL is installed and run the following command to connect to the Doris database:
If Kerberos authentication is enabled for the cluster (the cluster is in security mode), run the following command to connect to the Doris database:

export LIBMYSQL_ENABLE_CLEARTEXT_PLUGIN=1

mysql -uDatabase login user -pDatabase login user password -PDatabase connection port -hDoris FE instance IP address
- The database connection port is the query connection port of the Doris FE. You can log in to FusionInsight Manager, choose Cluster > Services > Doris > Configurations, and query the value of query_port of the Doris service.
- To obtain the IP address of the Doris FE instance, log in to FusionInsight Manager of the MRS cluster and choose Cluster > Services > Doris > Instances to view the IP address of any FE instance.
- You can also use the MySQL connection software or Doris WebUI to connect to the database.
Run the following command to create a database:
create database if not exists example_db;
Run the following command to create a table:
CREATE TABLE example_db.test_export_tbl (

`c1` int NOT NULL,

`c2` int NOT NULL,

`c3` string NOT NULL,

`c4` date NOT NULL

) ENGINE=OLAP

DUPLICATE KEY(`c1`, `c2`)

DISTRIBUTED BY HASH(`c1`) BUCKETS 1;
Run the following command to insert data:
insert into example_db.test_export_tbl values(1,1,1,"2020-02-21"),(2,2,2,"2020-03-21"),(3,3,3,"2020-04-21");
Run the following command to export data from the test_export_tbl table to HDFS:
EXPORT TABLE example_db.test_export_tbl

TO "hdfs:// IP address of the active NameNode instance:RPC port number /tmp/export/"

PROPERTIES

(

"label" = "label_exporthdfs_20230218031",

"column_separator"=",",

"columns" = "c1,c2,c3,c4",

"exec_mem_limit"="2147483648",

"timeout" = "3600"

)

with broker "broker_192_168_67_78"

(

"hadoop.security.authentication"="kerberos",

"kerberos_principal"="doris/hadoop.hadoop.com@HADOOP.COM",

"kerberos_keytab"="${BIGDATA_HOME}/FusionInsight_Doris_8.3.0/install/FusionInsight-Doris-1.2.3/doris-fe/bin/doris.keytab"

);
Run the following command to query the status of the export job:
SHOW EXPORT;

Related Configuration Parameters

Log in to FusionInsight Manager, choose Cluster > Services > Doris > Configurations > FE(Role) > Customization, and add the following parameters to the customized parameter fe.conf.customized.configs:

export_checker_interval_second: scheduling interval of the Export job scheduler. The default value is 5 seconds. After setting this parameter, restart the FE.
export_running_job_num_limit: specifies the maximum number of running export jobs. If the value is exceeded, the job waits and is in the PENDING state. The default value is 5, which can be adjusted during running.
export_task_default_timeout_second: default timeout interval of an export job. The default value is 2 hours, which can be adjusted during running.
export_tablet_num_per_task: maximum number of shards that a query plan is responsible for. The default value is 5.
label: label of an EXPORT task manually specified by a user. If this parameter is not specified, a label is automatically generated.

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