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    PolarDB:Asynchronous I/O for DDL

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    PolarDB:Asynchronous I/O for DDL

    Last Updated:Oct 12, 2026

    PolarDB provides the asynchronous I/O for DDL feature. A Data Definition Language (DDL) operation that creates an index on a large database table is usually time-consuming. You can use asynchronous I/O for DDL to reduce the time required to create an index.

    Prerequisites

    PolarDB clusters must meet one of the following version requirements:

    • PolarDB for MySQL 8.0.2, with a revision version of 8.0.2.2.6 or later.

    • PolarDB for MySQL 8.0.1, with a revision version of 8.0.1.1.29 or later.

    For more information about how to check the cluster version, see Query the engine version.

    Notes

    Asynchronous I/O for DDL is not supported for full-text indexes or spatial indexes.

    Usage

    You can configure asynchronous I/O for DDL by setting the following innodb_polar_ddl_async_io parameter. For instructions, see Set cluster and node parameters.

    Parameter

    Level

    Description

    innodb_polar_ddl_async_io

    Global

    Specifies whether to enable asynchronous I/O for DDL. Valid values:

    • ON: Enables asynchronous I/O for DDL.

    • OFF: Disables asynchronous I/O for DDL. This is the default value.

    Performance test

    • Test environment

      • A PolarDB for MySQL 8.0 cluster with 8 cores and 32 GB of memory.

      • The cluster has 50 TB of storage space.

    • Test table schema

      Run the following statement to create a table named table_1:

      CREATE TABLE `table_1` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`seller_id` bigint(20) DEFAULT NULL,
`seller_name` varchar(100) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
`gmt_create` varchar(30) DEFAULT NULL,
`update_time` varchar(30) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB;

    • Test table data

      Run the following statements to generate test data:

      delimiter ||
CREATE PROCEDURE populate_0(IN NUM INT)
BEGIN
DECLARE sid INT;
DECLARE suffix_name INT;
DECLARE i INT;
SET sid=1000;
SET suffix_name=10;
SET i=1;
START TRANSACTION;
WHILE i <= NUM
DO
INSERT INTO table_1(seller_id,seller_name,gmt_create,update_time) VALUES(sid,CONCAT('sellername',suffix_name),NOW(),NOW());
SET suffix_name=suffix_name+1;
SET sid=sid+1;
SET i=i+1;
END WHILE;
COMMIT;
END ||
delimiter ;
CALL populate_0(100000000) ;

    • Test method and results

      After the data is inserted, run the SQL statement alter table table_1 add index name_index (seller_name); with asynchronous I/O for DDL enabled and disabled to measure the improvement in DDL execution efficiency:

      Asynchronous I/O for DDL status

      Time (seconds)

      Asynchronous I/O for DDL enabled

      368

      Asynchronous I/O for DDL disabled

      485

    Contact us

    If you have questions about DDL operations, Contact us.