Load data from HDFS or cloud storage

StarRocks provides the loading method MySQL-based Broker Load to help you load dozens to hundreds of gigabytes of data from HDFS or cloud storage into StarRocks.

Broker Load runs in asynchronous loading mode. After you submit a load job, StarRocks asynchronously runs the job. You need to use the SHOW LOAD statement or the curl command to check the result of the job.

Broker Load supports loading one or more data files at a time and ensures the transactional atomicity of each load job that is run to load multiple data files. Atomicity means that the loading of multiple data files in one load job must all succeed or fail. It never happens that the loading of some data files succeeds while the loading of the other files fails.

Broker Load also supports data transformation at data loading. For more information, see Transform data at loading.

Background information

Broker Load requires a broker to set up a connection between your StarRocks cluster and your storage system. A broker is an independent, stateless service that is integrated with a file-system interface. With a broker, StarRocks can access and read data files that are stored in your storage system, and can use its own computing resources to pre-process and load the data of these data files.

Supported data file formats

Broker Load supports the following data file formats:

• CSV

• Parquet

• ORC

NOTE

For CSV data, take note of the following points:

• You can use a UTF-8 string, such as a comma (,), tab, or pipe (|), whose length does not exceed 50 bytes as a text delimiter.
• Null values are denoted by using \N. For example, a data file consists of three columns, and a record from that data file holds data in the first and third columns but no data in the second column. In this situation, you need to use \N in the second column to denote a null value. This means the record must be compiled as a,\N,b instead of a,,b. a,,b denotes that the second column of the record holds an empty string.

Supported storage systems

Broker Load supports the following storage systems:

• HDFS

• Amazon S3

• Google GCS

Prerequisites

Brokers are deployed in your StarRocks cluster.

You can use the SHOW BROKER statement to check for brokers that are deployed in your StarRocks cluster. If no brokers are deployed, you must deploy brokers by following the instructions provided in Deploy a broker.

In this topic, assume that a group of brokers collectively named 'mybroker' are deployed in your StarRocks cluster.

How it works

After you submit a load job to an FE, the FE generates a query plan, splits the query plan into portions based on the number of BEs and the size of the data file you want to load, and then assigns each portion of the query plan to a specific BE. During the load, each BE pulls the data of the data file by using the broker, pre-processes the data, and then loads the data into your StarRocks cluster. After all BEs finish their portions of the query plan, the FE determines whether the load job is successful.

The following figure shows the workflow of a Broker Load job.

Basic operations

Create a load job

This topic uses CSV as an example to describe how to load data. For information about how to load data in other file formats and about the syntax and parameter descriptions for Broker Load, see BROKER LOAD.

Note that in StarRocks some literals are used as reserved keywords by the SQL language. Do not directly use these keywords in SQL statements. If you want to use such a keyword in an SQL statement, enclose it in a pair of backticks (`). See Keywords.

Data examples

1. In your StarRocks database test_db, create StarRocks tables.

   a. Create a table named table1 that uses the Primary Key model. The table consists of three columns: id, name, and score, of which id is the primary key.

   MySQL [test_db]> CREATE TABLE `table1`
   (
       `id` int(11) NOT NULL COMMENT "user ID",
       `name` varchar(65533) NULL DEFAULT "" COMMENT "user name",
       `score` int(11) NOT NULL DEFAULT "0" COMMENT "user score"
   )
   ENGINE=OLAP
   PRIMARY KEY(`id`)
   DISTRIBUTED BY HASH(`id`) BUCKETS 10;

   b. Create a table named table2 that uses the Primary Key model. The table consists of two columns: id and city, of which id is the primary key.

   MySQL [test_db]> CREATE TABLE `table2`
   (
       `id` int(11) NOT NULL COMMENT "city ID",
       `city` varchar(65533) NULL DEFAULT "" COMMENT "city name"
   )
   ENGINE=OLAP
   PRIMARY KEY(`id`)
   DISTRIBUTED BY HASH(`id`) BUCKETS 10;

2. In your local file system, create CSV files.

   a. Create a CSV file named file1.csv. The file consists of three columns, which represent user ID, user name, and user score in sequence.

   1,Lily,23
   2,Rose,23
   3,Alice,24
   4,Julia,25

   b. Create a CSV file named file2.csv. The file consists of two columns, which represent city ID and city name in sequence.

   200,'Beijing'

3. Upload file1.csv and file2.csv to the /user/starrocks/ path of your HDFS cluster, to the input folder of your Amazon S3 bucket bucket_s3, and to the input folder of your Google GCS bucket bucket_gcs.

Load data from HDFS

Execute the following statement to load file1.csv and file2.csv from the /user/starrocks path of your HDFS cluster into table1 and table2, respectively:

LOAD LABEL test_db.label1
(
    DATA INFILE("hdfs://<hdfs_host>:<hdfs_port>/user/starrocks/file1.csv")
    INTO TABLE table1
    COLUMNS TERMINATED BY ","
    (id, city)
    ,
    DATA INFILE("hdfs://<hdfs_host>:<hdfs_port>/user/starrocks/file2.csv")
    INTO TABLE table2
    COLUMNS TERMINATED BY ","
    (id, name, score)
)
WITH BROKER "mybroker"
(
    "username" = "hdfs_username",
    "password" = "hdfs_password"
)
PROPERTIES
(
    "timeout" = "3600"
);

Load data from Amazon S3

Execute the following statement to load file1.csv and file2.csv from the input folder of your Amazon S3 bucket bucket_s3 into table1 and table2, respectively:

LOAD LABEL test_db.label2
(
    DATA INFILE("s3a://bucket_s3/input/file1.csv")
    INTO TABLE table1
    COLUMNS TERMINATED BY ","
    (id, city)
    ,
    DATA INFILE("s3a://bucket_s3/input/file2.csv")
    INTO TABLE table2
    COLUMNS TERMINATED BY ","
    (id, name, score)
)
WITH BROKER "mybroker"
(
    "fs.s3a.access.key" = "xxxxxxxxxxxxxxxxxxxx",
    "fs.s3a.secret.key" = "yyyyyyyyyyyyyyyyyyyy",
    "fs.s3a.endpoint" = "s3.ap-northeast-1.amazonaws.com"
);

NOTE

• Broker Load supports accessing AWS S3 only according to the S3A protocol. Therefore, when you load data from AWS S3, you must replace s3:// in the S3 URI you pass as a file path into DATA INFILE with s3a://.
• If the IAM role associated with your Amazon EC2 instance is granted permission to access your Amazon S3 bucket, you can leave fs.s3a.access.key and fs.s3a.secret.key unspecified.

Load data from Google GCS

Execute the following statement to load file1.csv and file2.csv from the input folder of your Google GCS bucket bucket_gcs into table1 and table2, respectively:

LOAD LABEL test_db.label3
(
    DATA INFILE("s3a://bucket_gcs/input/file1.csv")
    INTO TABLE table1
    COLUMNS TERMINATED BY ","
    (id, city)
    ,
    DATA INFILE("s3a://bucket_gcs/input/file2.csv")
    INTO TABLE table2
    COLUMNS TERMINATED BY ","
    (id, name, score)
)
WITH BROKER "mybroker"
(
    "fs.s3a.access.key" = "xxxxxxxxxxxxxxxxxxxx",
    "fs.s3a.secret.key" = "yyyyyyyyyyyyyyyyyyyy",
    "fs.s3a.endpoint" = "storage.googleapis.com"
);

NOTE

Broker Load supports accessing Google GCS only according to the S3A protocol. Therefore, when you load data from Google GCS, you must replace the prefix in the GCS URI you pass as a file path into DATA INFILE with s3a://.

Query data

After the load of data from your HDFS cluster, Amazon S3 bucket, or Google GCS bucket is complete, you can use the SELECT statement to query the data of the StarRocks tables to verify that the load is successful.

1. Execute the following statement to query the data of table1:

   MySQL [test_db]> SELECT * FROM table1;
   +------+-------+-------+
   | id   | name  | score |
   +------+-------+-------+
   |    1 | Lily  |    23 |
   |    2 | Rose  |    23 |
   |    3 | Alice |    24 |
   |    4 | Julia |    25 |
   +------+-------+-------+
   4 rows in set (0.00 sec)

2. Execute the following statement to query the data of table2:

   MySQL [test_db]> SELECT * FROM table2;
   +------+--------+
   | id   | city   |
   +------+--------+
   | 200  | Beijing|
   +------+--------+
   4 rows in set (0.01 sec)

Usage notes

The preceding load examples show how to load multiple data files into multiple destination tables. You can also load a single data file or all data files from a specified path into a single destination table. Suppose your Amazon S3 bucket bucket_s3 contains a folder named input. The input folder contains multiple data files, one of which is named file1.csv. These data files consist of the same number of columns as table1 and the columns from each of these data files can be mapped one on one in sequence to the columns from table1.

To load file1.csv into table1, execute the following statement:

LOAD LABEL test_db.label_7
(
    DATA INFILE("s3a://bucket_s3/input/file1.csv")
    INTO TABLE table1
    COLUMNS TERMINATED BY ","
    FORMAT AS "CSV"
)
WITH BROKER "mybroker"
(
    "fs.s3a.access.key" = "xxxxxxxxxxxxxxxxxxxx",
    "fs.s3a.secret.key" = "yyyyyyyyyyyyyyyyyyyy",
    "fs.s3a.endpoint" = "s3.ap-northeast-1.amazonaws.com"
)；

To load all data files from the input folder into table1, execute the following statement:

LOAD LABEL test_db.label_8
(
    DATA INFILE("s3a://bucket_s3/input/*")
    INTO TABLE table1
    COLUMNS TERMINATED BY ","
    FORMAT AS "CSV"
)
WITH BROKER "mybroker"
(
    "fs.s3a.access.key" = "xxxxxxxxxxxxxxxxxxxx",
    "fs.s3a.secret.key" = "yyyyyyyyyyyyyyyyyyyy",
    "fs.s3a.endpoint" = "s3.ap-northeast-1.amazonaws.com"
)；

View a load job

Broker Load allows you to view a lob job by using the SHOW LOAD statement or the curl command.

Use SHOW LOAD

For more information, see SHOW LOAD.

Use curl

The syntax is as follows:

curl --location-trusted -u root: \
    'http://<fe_host>:<fe_http_port>/api/<database_name>/_load_info?label=<label_name>'

For example, you can run the following command to view the information about a load job, whose label is label1, in the test_db database:

curl --location-trusted -u root: \
    'http://<fe_host>:<fe_http_port>/api/test_db/_load_info?label=label1'

The curl command returns the information about the load job as a JSON object jobInfo:

{"jobInfo":{"dbName":"default_cluster:test_db","tblNames":["table1_simple"],"label":"label1","state":"FINISHED","failMsg":"","trackingUrl":""},"status":"OK","msg":"Success"}%

The following table describes the parameters in jobInfo.

Cancel a load job

When a load job is not in the CANCELLED or FINISHED stage, you can use the CANCEL LOAD statement to cancel the job.

For example, you can execute the following statement to cancel a load job, whose label is label1, in the database test_db:

CANCEL LOAD
FROM test_db
WHERE LABEL = "label";

Job splitting and concurrent running

A Broker Load job can be split into one or more tasks that concurrently run. The tasks within a load job are run within a single transaction. They must all succeed or fail. StarRocks splits each load job based on how you declare data_desc in the LOAD statement:

• If you declare multiple data_desc parameters, each of which specifies a distinct table, a task is generated to load the data of each table.

• If you declare multiple data_desc parameters, each of which specifies a distinct partition for the same table, a task is generated to load the data of each partition.

Additionally, each task can be further split into one or more instances, which are evenly distributed to and concurrently run on the BEs of your StarRocks cluster. StarRocks splits each task based on the following FE configurations:

• min_bytes_per_broker_scanner: the minimum amount of data processed by each instance. The default amount is 64 MB.

• max_broker_concurrency: the maximum number of concurrent instances allowed in each task. The default maximum number is 100.

• load_parallel_instance_num: the number of concurrent instances allowed in each load job on an individual BE. The default number is 1.

  You can use the following formula to calculate the number of instances in an individual task:

  Number of instances in an individual task = min(Amount of data to be loaded by an individual task/min_bytes_per_broker_scanner,max_broker_concurrency,load_parallel_instance_num x Number of BEs)

In most cases, only one data_desc is declared for each load job, each load job is split into only one task, and the task is split into the same number of instances as the number of BEs.