AnalyticDB for MySQL:Use external tables to import data from OSS to AnalyticDB for MySQL Data Warehouse Edition

Prerequisites

• OSS is activated. A bucket and a directory are created in OSS. For more information, see Activate OSS, Create buckets, and Create directories.
• An AnalyticDB for MySQL Data Warehouse Edition (V3.0) cluster is created in the same virtual private cloud (VPC) as the OSS bucket. A whitelist is configured and a database account is created for the cluster. For more information, see Use AnalyticDB for MySQL.
• If the AnalyticDB for MySQL Data Warehouse Edition (V3.0) cluster is in elastic mode, ENI is turned on in the Network Information section of the Cluster Information page.

Description of sample data

uid;other
12;hello_world_1
27;hello_world_2
28;hello_world_3
33;hello_world_4
37;hello_world_5
40;hello_world_6
...             

Procedure

In this example, data in the oss_import_test_data.txt object is imported to an AnalyticDB for MySQL database named adb_demo.

1. Connect to the AnalyticDB for MySQL cluster. For more information, see Connect to an AnalyticDB for MySQL cluster.
2. Create a destination database. For more information, see Create a database.

   In this example, the database named adb_demo is used as the destination database in the AnalyticDB for MySQL cluster.

3. Create an external table. You can use the CREATE TABLE statement to create an OSS external table in the CSV, Parquet, or ORC format in the adb_demo database. For more information, see Create an OSS external table for a non-partitioned object and Create an OSS external table for a partitioned object.
4. Query OSS data. In this example, the external table oss_import_test_external_table is used.
   The syntax for querying external tables is the same as that for querying AnalyticDB for MySQL tables. You can use the following statement to query OSS external tables:

   SELECT uid, other FROM oss_import_test_external_table WHERE uid < 100 LIMIT 10;

   Note For queries on CSV, Parquet, and ORC objects, a larger amount of data causes greater performance loss. To improve query efficiency, we recommend that you perform the following steps to import the object to AnalyticDB for MySQL before you query data.
5. Create a destination table. You can create a destination table named adb_oss_import_test in the adb_demo database to store the data imported from OSS. The following statement can be used to create a destination table:

   CREATE TABLE IF NOT EXISTS adb_oss_import_test
   (
       uid string,
       other string
   )
   DISTRIBUTED BY HASH(uid);

6. Execute an INSERT statement to import data from OSS to AnalyticDB for MySQL.
   Important By default, INSERT INTO and INSERT OVERWRITE INTO SELECT statements import data synchronously. If hundreds of gigabytes of data is imported, the import may fail due to a disconnection from the client to the AnalyticDB for MySQL server. Therefore, if you want to import a large amount of data, we recommend that you execute the SUB JOB INSERT OVERWRITE INTO SELECT statement to import data asynchronously.

   • Method 1: Execute the INSERT INTO statement to import data. If the primary key has duplicate values, data is not repeatedly inserted and the INSERT INTO statement is equivalent to the INSERT IGNORE INTO statement. For more information, see INSERT INTO. Sample statement:

     INSERT INTO adb_oss_import_test
     SELECT * FROM oss_import_test_external_table;

   • Method 2: Execute the INSERT OVERWRITE INTO statement to import data. If the primary key has duplicate values, the original value is overwritten by the new value. Sample statement:

     INSERT OVERWRITE INTO adb_oss_import_test
     SELECT * FROM oss_import_test_external_table;

   • Method 3: Asynchronously execute the INSERT OVERWRITE INTO statement to import data. Typically, SUBMIT JOB is used to submit an asynchronous task. You can add a hint (/* direct_batch_load=true*/) before the data import statement to accelerate the task. For more information, see Asynchronous writing. Sample statement:

     SUBMIT JOB INSERT OVERWRITE INTO adb_oss_import_test
     SELECT * FROM oss_import_test_external_table;

     The following information is returned:

     +---------------------------------------+
     | job_id                                |
     +---------------------------------------+
     | 2020112122202917203100908203303****** |

     For more information about how to submit asynchronous tasks, see Asynchronously submit an import or export task.

Create an OSS external table for a non-partitioned object

• Create an OSS external table in the CSV format

  The following statement shows how to create an external table in the CSV format:

  CREATE TABLE IF NOT EXISTS oss_import_test_external_table
  (
      uid string,
      other string
  )
  ENGINE='OSS'
  TABLE_PROPERTIES='{
      "endpoint":"oss-cn-hangzhou-internal.aliyuncs.com",
      "url":"oss://<bucket-name>/adb/oss_import_test_data.csv",
      "accessid":"LTAIF****5FsE",
      "accesskey":"Ccw****iWjv",
      "delimiter":";",
      "skip_header_line_count":1
  }'; 

  Parameter	Required	Description
  ENGINE='OSS'	Yes	The storage engine used for the external table, which is OSS.
  TABLE_PROPERTIES		The connection information used by AnalyticDB for MySQL to access OSS.
  endpoint		The endpoint of the OSS bucket. Note AnalyticDB for MySQL can access OSS only from Elastic Compute Service (ECS) instances over VPCs. You can log on to the OSS console, find the bucket, and then view the endpoint on the Overview page.
  url		The absolute path of the source object or directory in OSS. We recommend that you use a forward slash (/) at the end of the absolute path of the directory. Examples: Object: oss://<bucket-name>/adb/oss_import_test_data.csv. Directory: oss://<bucket-name>/adb_data/.
  accessid		The AccessKey ID used to access the object or directory in OSS. For more information about how to obtain an AccessKey ID and an AccessKey secret, see Obtain an AccessKey pair.
  accesskey		The AccessKey secret used to access the object or directory in OSS.
  delimiter		The column delimiter of the object in the CSV format. For example, you can set the column delimiter to a comma (,).
  null_value	No	The NULL value of the object in the CSV format. By default, an empty string is defined as NULL, which is "null_value": "". Note This parameter is supported only for AnalyticDB for MySQL clusters of V3.1.4.2 or later. For more information, see Release notes.
  ossnull		The rule for defining the NULL value of the object in the CSV format. Default value: 1. Valid values: 1: EMPTY_SEPARATORS. Only empty strings are defined as NULL. For example, a,"",,c is expressed as "a","",NULL,"c" based on this rule. 2: EMPTY_QUOTES. Only quotation marks ("") are defined as NULL. For example, a,"",,c is expressed as "a",NULL,"","c" based on this rule. 3: BOTH. Both empty strings and quotation marks ("") are defined as NULL. For example, a,"",,c is expressed as "a",NULL,NULL,"c" based on this rule. 4: NEITHER. Empty strings and quotation marks ("") are not defined as NULL. For example, a,"",,c is expressed as "a","","","c" based on this rule. Note The preceding examples are provided on the premise of "null_value": "".
  skip_header_line_count		The number of header rows to skip when you import data. The first row of a CSV object is the table header. If you set this parameter to 1, the first row of the object is skipped when you import data. The default value of this parameter is 0, which indicates that no rows are skipped.
  oss_ignore_quote_and_escape		Specifies whether to ignore quotation marks (") and escape characters. The default value of this parameter is false, which indicates that quotation marks (") and escape characters are not ignored. Note This parameter is supported only for AnalyticDB for MySQL clusters of V3.1.4.2 or later. For more information, see Release notes.

  AnalyticDB for MySQL allows you to read and write data of TEXT files in Hive by using OSS external tables in the CSV format. The following statement can be used to create an external table:

  CREATE TABLE adb_csv_hive_format_oss (
    a tinyint,
    b smallint,
    c int,
    d bigint,
    e boolean,
    f float,
    g double,
    h varchar,
    i varchar, -- binary
    j timestamp,
    k DECIMAL(10, 4),
    l varchar, -- char(10)
    m varchar, -- varchar(100)
    n date
  ) ENGINE = 'OSS' TABLE_PROPERTIES='{
      "format": "csv",
      "endpoint":"oss-cn-hangzhou-internal.aliyuncs.com",
      "accessid":"LTAIF****5FsE",
      "accesskey":"Ccw****iWjv",
      "url":"oss://<bucket-name>/adb/adb_csv_hive_format_oss.txt",
      "delimiter": "\\1",
      "null_value": "\\\\N",
      "oss_ignore_quote_and_escape": "true",
      "ossnull": 2,
  }';

  Note When you create an OSS external table in the CSV format to read and write data of a TEXT file in Hive, take note of the following items:

  • The default column delimiter for the TEXT file in Hive is \1. If you want to use the OSS external table to read and write data of the TEXT file in Hive, \1 must be escaped to \\1 for the delimiter parameter.
  • By default, the NULL value of the TEXT file in Hive is \N. If you want to use the OSS external table to read and write data of the TEXT file in Hive, \N must be escaped to \\\\N for the null_value parameter.
  • The BINARY, CHAR(N), and VARCHAR(N) data types in Hive all correspond to the VARCHAR data type in AnalyticDB for MySQL. Other basic data types in Hive such as BOOLEAN are the same as those in AnalyticDB for MySQL.
• Create an OSS external table in the Parquet or ORC format
  The following statement shows how to create an external table in the Parquet format:

  CREATE TABLE IF NOT EXISTS oss_import_test_external_table
  (
      uid string,
      other string
  )
  ENGINE='OSS'
  TABLE_PROPERTIES='{
      "endpoint":"oss-cn-hangzhou-internal.aliyuncs.com",
      "url":"oss://<bucket-name>/adb_data/",
      "accessid":"LTAIF****5FsE",
      "accesskey":"Ccw****iWjv",
      "format":"parquet"
  }';

  Parameter	Description
  ENGINE= 'OSS'	The storage engine used for the external table, which is OSS.
  TABLE_PROPERTIES	The connection information used by AnalyticDB for MySQL to access OSS.
  endpoint	The endpoint of the OSS bucket. Note AnalyticDB for MySQL can access OSS only from ECS instances over VPCs. You can log on to the OSS console, find the bucket, and then view the endpoint on the Overview page.
  url	The absolute path of the source object or directory in OSS. We recommend that you use a forward slash (/) at the end of the absolute path of the directory. Examples: Object: oss://<bucket-name>/adb/oss_import_test_data.parquet. Directory: oss://<bucket-name>/adb_data/.
  accessid	The AccessKey ID used to access the object or directory in OSS. For more information about how to obtain an AccessKey ID and an AccessKey secret, see Obtain an AccessKey pair.
  accesskey	The AccessKey secret used to access the object or directory in OSS.
  format	The format of the object. When you create an external table in the Parquet format, you must set this parameter to parquet. When you create an external table in the ORC format, you must set this parameter to orc. Note If the format parameter is not specified, the CSV format is used.

  Note

  • The column names used in the statement to create an external table must be the same as those in the Parquet or ORC file. Column names are case-insensitive. The sequence of the columns in the statement must be the same as that in the Parquet or ORC file.
  • When you create an external table, you can choose only specific columns in a Parquet or ORC file as the columns of the external table. Columns that are not selected in the Parquet or ORC file are not imported.
  • If the statement used to create an external table contains a column that is not in the Parquet or ORC file, NULL is returned for this column.
  The following table describes the mappings between data types in Parquet and AnalyticDB for MySQL V3.0.

  Basic type in Parquet	Logical type in Parquet	Data type in AnalyticDB for MySQL V3.0
  BOOLEAN	N/A	BOOLEAN
  INT32	INT_8	TINYINT
  INT32	INT_16	SMALLINT
  INT32	N/A	INT or INTEGER
  INT64	N/A	BIGINT
  FLOAT	N/A	FLOAT
  DOUBLE	N/A	DOUBLE
  FIXED_LEN_BYTE_ARRAY BINARY INT64 INT32	DECIMAL	DECIMAL
  BINARY	UTF-8	VARCHAR STRING JSON (JSON is available if an object in the Parquet format contains a column in the JSON format.)
  INT32	DATE	DATE
  INT64	TIMESTAMP_MILLIS	TIMESTAMP or DATETIME
  INT96	N/A	TIMESTAMP or DATETIME

  Important External tables in the Parquet format do not support the STRUCT data type. Tables cannot be created for this data type.
  The following table describes the mappings between data types in ORC and AnalyticDB for MySQL V3.0.

  Data type in ORC	Data type in AnalyticDB for MySQL V3.0
  BOOLEAN	BOOLEAN
  BYTE	TINYINT
  SHORT	SMALLINT
  INT	INT or INTEGER
  LONG	BIGINT
  DECIMAL	DECIMAL
  FLOAT	FLOAT
  DOUBLE	DOUBLE
  BINARY STRING VARCHAR	VARCHAR STRING JSON (JSON is available if an object in the ORC format contains a column in the JSON format.)
  TIMESTAMP	TIMESTAMP or DATETIME
  DATE	DATE

  Important ORC external tables that use the LIST, STRUCT, or UNION data type cannot be created. You can create ORC external tables that use the MAP data type, but cannot perform queries on the tables.

Create an OSS external table for a partitioned object

parquet_partition_classic/
├── p1=2020-01-01
│   ├── p2=4
│   │   ├── p3=SHANGHAI
│   │   │   ├── 000000_0
│   │   │   └── 000000_1
│   │   └── p3=SHENZHEN
│   │       └── 000000_0
│   └── p2=6
│       └── p3=SHENZHEN
│           └── 000000_0
├── p1=2020-01-02
│   └── p2=8
│       ├── p3=SHANGHAI
│       │   └── 000000_0
│       └── p3=SHENZHEN
│           └── 000000_0
└── p1=2020-01-03
    └── p2=6
        ├── p2=HANGZHOU
        └── p3=SHENZHEN
            └── 000000_0

CREATE TABLE IF NOT EXISTS oss_parquet_partition_table
(
  uid varchar,
  other varchar,
  p1 date,
  p2 int,
  p3 varchar
)
ENGINE='OSS'
TABLE_PROPERTIES='{
  "endpoint":"oss-cn-hangzhou-internal.aliyuncs.com",
  "url":"oss://<bucket-name>/adb/oss_parquet_data_dir",
  "accessid":"LTAIF****5FsE",
  "accesskey":"Ccw****iWjv",
  "format":"parquet",
  "partition_column":"p1, p2, p3"
}';