Creating an OBS Table Using the Hive Syntax

Function

This statement is used to create an OBS table using the Hive syntax. The main differences between the DataSource and the Hive syntax lie in the supported data formats and the number of supported partitions. For details, see syntax and precautions.

You are advised to use the OBS parallel file system for storage. A parallel file system is a high-performance file system that provides latency in milliseconds, TB/s-level bandwidth, and millions of IOPS. It applies to interactive big data analysis scenarios.

Precautions

• The size of a table is calculated when the table is created.
• When data is added, the table size will not be changed.
• You can check the table size on OBS.
• Table properties cannot be specified using CTAS table creation statements.
• Instructions on using partitioned tables:
  • When you create a partitioned table, ensure that the specified column in PARTITIONED BY is not a column in the table and the data type is specified. The partition column supports only the open-source Hive table types including string, boolean, tinyint, smallint, short, int, bigint, long, decimal, float, double, date, and timestamp.
  • Multiple partition fields can be specified. The partition fields need to be specified after the PARTITIONED BY keyword, instead of the table name. Otherwise, an error occurs.
  • A maximum of 200,000 partitions can be created in a single table.
  • Spark 3.3 or later supports creating partitioned tables using CTAS statements of the Hive syntax.

Syntax

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CREATE [EXTERNAL] TABLE [IF NOT EXISTS] [db_name.]table_name 
  [(col_name1 col_type1 [COMMENT col_comment1], ...)]
  [COMMENT table_comment] 
  [PARTITIONED BY (col_name2 col_type2, [COMMENT col_comment2], ...)] 
  [ROW FORMAT row_format]
  [STORED AS file_format] 
  LOCATION 'obs_path'
  [TBLPROPERTIES (key = value)]
  [AS select_statement]
row_format:
  : SERDE serde_cls [WITH SERDEPROPERTIES (key1=val1, key2=val2, ...)]
  | DELIMITED [FIELDS TERMINATED BY char [ESCAPED BY char]]
      [COLLECTION ITEMS TERMINATED BY char]
      [MAP KEYS TERMINATED BY char]
      [LINES TERMINATED BY char]
      [NULL DEFINED AS char]

Keywords

• EXTERNAL: Creates an OBS table.
• IF NOT EXISTS: Prevents system errors when the created table exists.
• COMMENT: Field or table description.
• PARTITIONED BY: Partition field.
• ROW FORMAT: Row data format.
• STORED AS: Specifies the format of the file to be stored. Currently, only the TEXTFILE, AVRO, ORC, SEQUENCEFILE, RCFILE, and PARQUET format are supported.
• LOCATION: Specifies the path of OBS. This keyword is mandatory when you create OBS tables.
• TBLPROPERTIES: Allows you to add the key/value properties to a table.
  • You can use this statement to enable the multiversion function to back up and restore table data. After the multiversion function is enabled, the system automatically backs up table data when you delete or modify the data using insert overwrite or truncate, and retains the data for a certain period. You can quickly restore data within the retention period. For details about the SQL syntax for the multiversion function, see Enabling or Disabling Multiversion Backup and Backing Up and Restoring Data of Multiple Versions.

    When creating an OBS table, you can use TBLPROPERTIES ("dli.multi.version.enable"="true") to enable multiversion. For details, see the following example.

    Table 1 TBLPROPERTIES parameters

    Key	Value
    dli.multi.version.enable	true: Enable the multiversion backup function. false: Disable the multiversion backup function.
    comment	Description of the table
    orc.compress	An attribute of the ORC table, which specifies the compression mode of the ORC storage. Available values are as follows: ZLIB SNAPPY NONE PARQUET
    auto.purge	If this parameter is set to true, the deleted or overwritten data is removed and will not be dumped to the recycle bin.

• AS: You can run the CREATE TABLE AS statement to create a table.

Parameters

Example 1: Creating an OBS Non-Partitioned Table

Example description: Create an OBS non-partitioned table named table1 and use the STORED AS keyword to set the storage format of the table to orc.

In practice, you can store OBS tables in textfile, avro, orc, sequencefile, rcfile, or parquet format.

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CREATE TABLE IF NOT EXISTS table1 (
    col_1   STRING,
    col_2   INT
)
STORED AS orc
LOCATION 'obs://bucketName/filePath';

Example 2: Creating an OBS Partitioned Table

Example description: Create a partitioned table named student, which is partitioned using facultyNo and classNo.

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CREATE TABLE IF NOT EXISTS student(
    id      INT,
    name    STRING
)
STORED AS avro
LOCATION 'obs://bucketName/filePath'
PARTITIONED BY (
    facultyNo   INT,
    classNo     INT
);

Example 3: Using CTAS to Create an OBS Table Using All or Part of the Data in the Source Table

Example description: Based on the OBS table table1 created in Example 1: Creating an OBS Non-Partitioned Table, use the CTAS syntax to copy data from table1 to table1_ctas.

When using CTAS to create a table, you can ignore the syntax used to create the table being copied. This means that regardless of the syntax used to create table1, you can use the DataSource syntax to create table1_ctas.

In addition, in this example, the storage format of table1 is orc, and the storage format of table1_ctas may be sequencefile or parquet. This means that the storage format of the table created by CTAS may be different from that of the original table.

Use the SELECT statement following the AS keyword to select required data and insert the data to table1_ctas.

The SELECT syntax is as follows: SELECT <Column name > FROM <Table name > WHERE <Related filter criteria>.

• In this example, SELECT * FROM table1 is used. * indicates that all columns are selected from table1 and all data in table1 is inserted into table1_ctas.

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  CREATE TABLE IF NOT EXISTS table1_ctas STORED AS sequencefile LOCATION 'obs://bucketName/filePath' AS SELECT * FROM table1;

• To filter and insert data into table1_ctas in a customized way, you can use the following SELECT statement: SELECT col_1 FROM table1 WHERE col_1 = 'Ann'. This will allow you to select only col_1 from table1 and insert data into table1_ctas where the value equals 'Ann'.

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  CREATE TABLE IF NOT EXISTS table1_ctas USING parquet OPTIONS (path 'obs:// bucketName/filePath') AS SELECT col_1 FROM table1 WHERE col_1 = 'Ann';

Example 4: Creating an OBS Non-Partitioned Table and Customizing the Data Type of a Column Field

Example description: Create an OBS non-partitioned table named table2. You can customize the native data types of column fields based on service requirements.

• STRING, CHAR, or VARCHAR can be used for text characters.
• TIMESTAMP or DATE can be used for time characters.
• INT, SMALLINT/SHORT, BIGINT/LONG, or TINYINT can be used for integer characters.
• FLOAT, DOUBLE, or DECIMAL can be used for decimal calculation.
• BOOLEAN can be used if only logical switches are involved.

For details, see "Data Types" > "Primitive Data Types".

For details, see Primitive Data Types.

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CREATE TABLE IF NOT EXISTS table2 (
    col_01  STRING,
    col_02  CHAR (2),
    col_03  VARCHAR (32),
    col_04  TIMESTAMP,
    col_05  DATE,
    col_06  INT,
    col_07  SMALLINT,
    col_08  BIGINT,
    col_09  TINYINT,
    col_10  FLOAT,
    col_11  DOUBLE,
    col_12  DECIMAL (10, 3),
    col_13  BOOLEAN
)
STORED AS parquet
LOCATION 'obs://bucketName/filePath';

Example 5: Creating an OBS Partitioned Table and Customizing TBLPROPERTIES Parameters

Example description: Create an OBS partitioned table named table3 and partition the table based on col_3. Set dli.multi.version.enable, comment, orc.compress, and auto.purge in TBLPROPERTIES.

• dli.multi.version.enable: In this example, set this parameter to true, indicating that the DLI data versioning function is enabled for table data backup and restoration.
• comment: table description, which can be modified later.
• orc.compress: compression mode of the orc format, which is ZLIB in this example.
• auto.purge: In this example, set this parameter to true, indicating that data that is deleted or overwritten will bypass the recycle bin and be permanently deleted.

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CREATE TABLE IF NOT EXISTs table3 (
    col_1 STRING,
    col_2 STRING
)
PARTITIONED BY (col_3 DATE)
STORED AS rcfile
LOCATION 'obs://bucketName/filePath'
TBLPROPERTIES (
    dli.multi.version.enable  = true,
    comment                   = 'Created by dli',
    orc.compress              = 'ZLIB',
    auto.purge                = true
);

Example 6: Creating a Non-Partitioned Table in textfile Format and Setting ROW FORMAT

Example description: Create a non-partitioned table named table4 in the textfile format and set ROW FORMAT (the ROW FORMAT function is available only for textfile tables).

• FIELDS: columns in a table. Each field has a name and data type. Fields in a table are separated by slashes (/).
• COLLECTION ITEMS: A collection item refers to an element in a group of data, which can be an array, a list, or a collection. Collection items in a table are separated by $.
• MAP KEYS: A map key is a data structure of key-value pairs and is used to store a group of associated data. Map keys in a table are separated by number signs (#).
• LINES: rows in a table. Each row contains a group of field values. Rows in a table end with \n. (Note that only \n can be used as the row separator.)
• NULL: a special value that represents a missing or unknown value. In a table, NULL indicates that the field has no value or the value is unknown. When there is a null value in the data, it is represented by the string null.

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CREATE TABLE IF NOT EXISTS table4 (
    col_1   STRING,
    col_2   INT
)
STORED AS textfile
LOCATION 'obs://bucketName/filePath'
ROW FORMAT
DELIMITED FIELDS TERMINATED   BY '/'
COLLECTION ITEMS TERMINATED   BY '$'
MAP KEYS TERMINATED           BY '#'
LINES TERMINATED              BY '\n'
NULL DEFINED                  AS 'null';