FILES

Description

Defines data files in remote storage.

From v3.1.0 onwards, StarRocks supports defining read-only files in remote storage using the table function FILES(). It can access remote storage with the path-related properties of the files, infers the table schema of the data in the files, and returns the data rows. You can directly query the data rows using SELECT, load the data rows into an existing table using INSERT, or create a new table and load the data rows into it using CREATE TABLE AS SELECT.

From v3.2.0 onwards, FILES() supports writing data into files in remote storage. You can use INSERT INTO FILES() to unload data from StarRocks to remote storage.

Currently, the FILES() function supports the following data sources and file formats:

• Data sources:
  • HDFS
  • AWS S3
  • Google Cloud Storage
  • Other S3-compatible storage system
  • Microsoft Azure Blob Storage
• File formats:
  • Parquet
  • ORC (Currently not supported for unloading data)

Syntax

• Data loading:

  FILES( data_location , data_format [, StorageCredentialParams ] [, columns_from_path ] )

• Data unloading:

  FILES( data_location , data_format [, StorageCredentialParams ] , unload_data_param )

Parameters

All parameters are in the "key" = "value" pairs.

data_location

The URI used to access the files. You can specify a path or a file.

• To access HDFS, you need to specify this parameter as:

  "path" = "hdfs://<hdfs_host>:<hdfs_port>/<hdfs_path>"
  -- Example: "path" = "hdfs://127.0.0.1:9000/path/file.parquet"

• To access AWS S3:

  • If you use the S3 protocol, you need to specify this parameter as:

    "path" = "s3://<s3_path>"
    -- Example: "path" = "s3://path/file.parquet"

  • If you use the S3A protocol, you need to specify this parameter as:

    "path" = "s3a://<s3_path>"
    -- Example: "path" = "s3a://path/file.parquet"

• To access Google Cloud Storage, you need to specify this parameter as:

  "path" = "s3a://<gcs_path>"
  -- Example: "path" = "s3a://path/file.parquet"

• To access Azure Blob Storage:

  • If your storage account allows access over HTTP, you need to specify this parameter as:

    "path" = "wasb://<container>@<storage_account>.blob.core.windows.net/<blob_path>"
    -- Example: "path" = "wasb://testcontainer@testaccount.blob.core.windows.net/path/file.parquet"

  • If your storage account allows access over HTTPS, you need to specify this parameter as:

    "path" = "wasbs://<container>@<storage_account>.blob.core.windows.net/<blob_path>"
    -- Example: "path" = "wasbs://testcontainer@testaccount.blob.core.windows.net/path/file.parquet"

data_format

The format of the data file. Valid values: parquet and orc.

schema_detect

From v3.2 onwards, FILES() supports automatic schema detection and unionization of the same batch of data files. StarRocks first detects the schema of the data by sampling certain data rows of a random data file in the batch. Then, StarRocks unionizes the columns from all the data files in the batch.

You can configure the sampling rule using the following parameters:

• auto_detect_sample_files: the number of random data files to sample in each batch. Range: [0, + ∞]. Default: 1.
• auto_detect_sample_rows: the number of data rows to scan in each sampled data file. Range: [0, + ∞]. Default: 500.

After the sampling, StarRocks unionizes the columns from all the data files according to these rules:

• For columns with different column names or indices, each column is identified as an individual column, and, eventually, the union of all individual columns is returned.
• For columns with the same column name but different data types, they are identified as the same column but with a general data type on a relative fine granularity level. For example, if the column col1 in file A is INT but DECIMAL in file B, DOUBLE is used in the returned column.
  • All integer columns will be unionized as an integer type on an overall rougher granularity level.
  • Integer columns together with FLOAT type columns will be unionized as the DECIMAL type.
  • String types are used for unionizing other types.
• Generally, the STRING type can be used to unionize all data types.

You can refer to Example 6.

If StarRocks fails to unionize all the columns, it generates a schema error report that includes the error information and all the file schemas.

CAUTION

All data files in a single batch must be of the same file format.

StorageCredentialParams

The authentication information used by StarRocks to access your storage system.

StarRocks currently supports accessing HDFS with the simple authentication, accessing AWS S3 and GCS with the IAM user-based authentication, and accessing Azure Blob Storage with Shared Key.

• Use the simple authentication to access HDFS:

  "hadoop.security.authentication" = "simple",
  "username" = "xxxxxxxxxx",
  "password" = "yyyyyyyyyy"

  Key	Required	Description
  hadoop.security.authentication	No	The authentication method. Valid value: simple (Default). simple represents simple authentication, meaning no authentication.
  username	Yes	The username of the account that you want to use to access the NameNode of the HDFS cluster.
  password	Yes	The password of the account that you want to use to access the NameNode of the HDFS cluster.

• Use the IAM user-based authentication to access AWS S3:

  "aws.s3.access_key" = "AAAAAAAAAAAAAAAAAAAA",
  "aws.s3.secret_key" = "BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB",
  "aws.s3.region" = "<s3_region>"

  Key	Required	Description
  aws.s3.access_key	Yes	The Access Key ID that you can use to access the Amazon S3 bucket.
  aws.s3.secret_key	Yes	The Secret Access Key that you can use to access the Amazon S3 bucket.
  aws.s3.region	Yes	The region in which your AWS S3 bucket resides. Example: us-west-2.

• Use the IAM user-based authentication to access GCS:

  "fs.s3a.access.key" = "AAAAAAAAAAAAAAAAAAAA",
  "fs.s3a.secret.key" = "BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB"
  "fs.s3a.endpoint" = "<gcs_endpoint>"

  Key	Required	Description
  fs.s3a.access.key	Yes	The Access Key ID that you can use to access the GCS bucket.
  fs.s3a.secret.key	Yes	The Secret Access Key that you can use to access the GCS bucket.
  fs.s3a.endpoint	Yes	The endpoint that you can use to access the GCS bucket. Example: storage.googleapis.com. Do not specify https in the endpoint address.

• Use Shared Key to access Azure Blob Storage:

  "azure.blob.storage_account" = "<storage_account>",
  "azure.blob.shared_key" = "<shared_key>"

  Key	Required	Description
  azure.blob.storage_account	Yes	The name of the Azure Blob Storage account.
  azure.blob.shared_key	Yes	The Shared Key that you can use to access the Azure Blob Storage account.

columns_from_path

From v3.2 onwards, StarRocks can extract the value of a key/value pair from the file path as the value of a column.

"columns_from_path" = "<column_name> [, ...]"

Suppose the data file file1 is stored under a path in the format of /geo/country=US/city=LA/. You can specify the columns_from_path parameter as "columns_from_path" = "country, city" to extract the geographic information in the file path as the value of columns that are returned. For further instructions, see Example 4.

unload_data_param

From v3.2 onwards, FILES() supports defining writable files in remote storage for data unloading.

-- Supported from v3.2 onwards.
unload_data_param::=
    "compression" = "<compression_method>",
    "partition_by" = "<column_name> [, ...]",
    "single" = { "true" | "false" } ,
    "target_max_file_size" = "<int>"

Key	Required	Description
compression	Yes	The compression method to use when unloading data. Valid values: uncompressed: No compression algorithm is used. gzip: Use the gzip compression algorithm. snappy: Use the SNAPPY compression algorithm. zstd: Use the Zstd compression algorithm. lz4: Use the LZ4 compression algorithm.
partition_by	No	The list of columns that are used to partition data files into different storage paths. Multiple columns are separated by commas (,). FILES() extracts the key/value information of the specified columns and stores the data files under the storage paths featured with the extracted key/value pair. For further instructions, see Example 5.
single	No	Whether to unload the data into a single file. Valid values: true: The data is stored in a single data file. false (Default): The data is stored in multiple files if the amount of data unloaded exceeds 512 MB.
target_max_file_size	No	The best-effort maximum size of each file in the batch to be unloaded. Unit: Bytes. Default value: 1073741824 (1 GB). When the size of data to be unloaded exceeds this value, the data will be divided into multiple files, and the size of each file will not significantly exceed this value. Introduced in v3.2.7.

Return

When used with SELECT, FILES() returns the data in the file as a table.

• When querying Parquet or ORC files, you can directly specify the name of the desired columns in the SELECT statement, or specify * to obtain data from all columns.

  SELECT * FROM FILES(
      "path" = "s3://inserttest/parquet/file2.parquet",
      "format" = "parquet",
      "aws.s3.access_key" = "AAAAAAAAAAAAAAAAAAAA",
      "aws.s3.secret_key" = "BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB",
      "aws.s3.region" = "us-west-2"
  )
  WHERE c1 IN (101,105);
  +------+------+---------------------+
  | c1   | c2   | c3                  |
  +------+------+---------------------+
  |  101 |    9 | 2018-05-15T18:30:00 |
  |  105 |    6 | 2018-05-15T18:30:00 |
  +------+------+---------------------+
  2 rows in set (0.29 sec)
  
  SELECT c1, c3 FROM FILES(
      "path" = "s3://inserttest/parquet/file2.parquet",
      "format" = "parquet",
      "aws.s3.access_key" = "AAAAAAAAAAAAAAAAAAAA",
      "aws.s3.secret_key" = "BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB",
      "aws.s3.region" = "us-west-2"
  );
  +------+---------------------+
  | c1   | c3                  |
  +------+---------------------+
  |  101 | 2018-05-15T18:30:00 |
  |  102 | 2018-05-15T18:30:00 |
  |  103 | 2018-05-15T18:30:00 |
  |  104 | 2018-05-15T18:30:00 |
  |  105 | 2018-05-15T18:30:00 |
  |  106 | 2018-05-15T18:30:00 |
  |  107 | 2018-05-15T18:30:00 |
  |  108 | 2018-05-15T18:30:00 |
  |  109 | 2018-05-15T18:30:00 |
  |  110 | 2018-05-15T18:30:00 |
  +------+---------------------+
  10 rows in set (0.55 sec)

Usage notes

From v3.2 onwards, FILES() further supports complex data types including ARRAY, JSON, MAP, and STRUCT in addition to basic data types.

Examples

Example 1

Query the data from the Parquet file parquet/par-dup.parquet within the AWS S3 bucket inserttest:

MySQL > SELECT * FROM FILES(
     "path" = "s3://inserttest/parquet/par-dup.parquet",
     "format" = "parquet",
     "aws.s3.access_key" = "AAAAAAAAAAAAAAAAAAAA",
     "aws.s3.secret_key" = "BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB",
     "aws.s3.region" = "us-west-2"
);
+------+---------------------------------------------------------+
| c1   | c2                                                      |
+------+---------------------------------------------------------+
|    1 | {"1": "key", "1": "1", "111": "1111", "111": "aaaa"}    |
|    2 | {"2": "key", "2": "NULL", "222": "2222", "222": "bbbb"} |
+------+---------------------------------------------------------+
2 rows in set (22.335 sec)

Example 2

Insert the data rows from the Parquet file parquet/insert_wiki_edit_append.parquet within the AWS S3 bucket inserttest into the table insert_wiki_edit:

MySQL > INSERT INTO insert_wiki_edit
    SELECT * FROM FILES(
        "path" = "s3://inserttest/parquet/insert_wiki_edit_append.parquet",
        "format" = "parquet",
        "aws.s3.access_key" = "AAAAAAAAAAAAAAAAAAAA",
        "aws.s3.secret_key" = "BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB",
        "aws.s3.region" = "us-west-2"
);
Query OK, 2 rows affected (23.03 sec)
{'label':'insert_d8d4b2ee-ac5c-11ed-a2cf-4e1110a8f63b', 'status':'VISIBLE', 'txnId':'2440'}

Example 3

Create a table named ctas_wiki_edit and insert the data rows from the Parquet file parquet/insert_wiki_edit_append.parquet within the AWS S3 bucket inserttest into the table:

MySQL > CREATE TABLE ctas_wiki_edit AS
    SELECT * FROM FILES(
        "path" = "s3://inserttest/parquet/insert_wiki_edit_append.parquet",
        "format" = "parquet",
        "aws.s3.access_key" = "AAAAAAAAAAAAAAAAAAAA",
        "aws.s3.secret_key" = "BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB",
        "aws.s3.region" = "us-west-2"
);
Query OK, 2 rows affected (22.09 sec)
{'label':'insert_1a217d70-2f52-11ee-9e4a-7a563fb695da', 'status':'VISIBLE', 'txnId':'3248'}

Example 4

Query the data from the Parquet file /geo/country=US/city=LA/file1.parquet (which only contains two columns -id and user), and extract the key/value information in its path as columns returned.

SELECT * FROM FILES(
    "path" = "hdfs://xxx.xx.xxx.xx:9000/geo/country=US/city=LA/file1.parquet",
    "format" = "parquet",
    "hadoop.security.authentication" = "simple",
    "username" = "xxxxx",
    "password" = "xxxxx",
    "columns_from_path" = "country, city"
);
+------+---------+---------+------+
| id   | user    | country | city |
+------+---------+---------+------+
|    1 | richard | US      | LA   |
|    2 | amber   | US      | LA   |
+------+---------+---------+------+
2 rows in set (3.84 sec)

Example 5

Unload all data rows in sales_records as multiple Parquet files under the path /unload/partitioned/ in the HDFS cluster. These files are stored in different subpaths distinguished by the values in the column sales_time.

INSERT INTO 
FILES(
    "path" = "hdfs://xxx.xx.xxx.xx:9000/unload/partitioned/",
    "format" = "parquet",
    "hadoop.security.authentication" = "simple",
    "username" = "xxxxx",
    "password" = "xxxxx",
    "compression" = "lz4",
    "partition_by" = "sales_time"
)
SELECT * FROM sales_records;

Example 6

Automatic schema detection and Unionization.

The following example is based on two Parquet files in the S3 bucket:

• File 1 contains three columns - INT column c1, FLOAT column c2, and DATE column c3.

c1,c2,c3
1,0.71173,2017-11-20
2,0.16145,2017-11-21
3,0.80524,2017-11-22
4,0.91852,2017-11-23
5,0.37766,2017-11-24
6,0.34413,2017-11-25
7,0.40055,2017-11-26
8,0.42437,2017-11-27
9,0.67935,2017-11-27
10,0.22783,2017-11-29

• File 2 contains three columns - INT column c1, INT column c2, and DATETIME column c3.

c1,c2,c3
101,9,2018-05-15T18:30:00
102,3,2018-05-15T18:30:00
103,2,2018-05-15T18:30:00
104,3,2018-05-15T18:30:00
105,6,2018-05-15T18:30:00
106,1,2018-05-15T18:30:00
107,8,2018-05-15T18:30:00
108,5,2018-05-15T18:30:00
109,6,2018-05-15T18:30:00
110,8,2018-05-15T18:30:00

Use a CTAS statement to create a table named test_ctas_parquet and insert the data rows from the two Parquet files into the table:

CREATE TABLE test_ctas_parquet AS
SELECT * FROM FILES(
    "path" = "s3://inserttest/parquet/*",
    "format" = "parquet",
    "aws.s3.access_key" = "AAAAAAAAAAAAAAAAAAAA",
    "aws.s3.secret_key" = "BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB",
    "aws.s3.region" = "us-west-2"
);

View the table schema of test_ctas_parquet:

SHOW CREATE TABLE test_ctas_parquet\G

*************************** 1. row ***************************
       Table: test_ctas_parquet
Create Table: CREATE TABLE `test_ctas_parquet` (
  `c1` bigint(20) NULL COMMENT "",
  `c2` decimal(38, 9) NULL COMMENT "",
  `c3` varchar(1048576) NULL COMMENT ""
) ENGINE=OLAP 
DUPLICATE KEY(`c1`, `c2`)
COMMENT "OLAP"
DISTRIBUTED BY RANDOM
PROPERTIES (
"bucket_size" = "4294967296",
"compression" = "LZ4",
"replication_num" = "3"
);

The result shows that the c2 column, which contains both FLOAT and INT data, is merged as a DECIMAL column, and c3, which contains both DATE and DATETIME data, is merged as a VARCHAR column.