This topic describes the limits on PolarDB for MySQL.

Product edition Node specification Memory consumed by the file system Maximum number of files Maximum number of connections
Cluster Edition polar.mysql.x4.medium 850 MB 1,024,000 2,000
polar.mysql.x4.large 2,048,000 5,000
polar.mysql.x4.xlarge 4,096,000 10,000
polar.mysql.x8.xlarge 6,144,000 10,000
polar.mysql.x8.2xlarge 20,480,000 20,000
polar.mysql.x8.4xlarge 20,480,000 64,000
polar.mysql.x8.8xlarge 20,480,000 64,000
polar.mysql.x8.12xlarge 20,480,000 64,000
Single Node polar.mysql.s2.large 1,024,000 1,200
Archive Database polar.mysql.a4.large 10,240,000 8,000
polar.mysql.a4.xlarge 20,480,000 10,000
polar.mysql.a8.xlarge 20,480,000 10,000
polar.mysql.a8.2xlarge 20,480,000 20,000
polar.mysql.a8.4xlarge 20,480,000 64,000
polar.mysql.a8.8xlarge 20,480,000 64,000
polar.mysql.a8.12xlarge 20,480,000 64,000

Description:

  • Memory consumed by the file system

    The amount of memory that is consumed by the file system when the upper limit of the storage for a cluster is reached. In this case, the cluster handles normal read and write requests (without performance stress testing and DDL operations on large tables). If the upper limit of the storage is not reached, the consumed amount of memory is less than the specified value of this parameter.

  • Maximum number of files
    User files, about 100 database system files, and log files are included. To view the number of log files, run the SHOW POLAR LOGS command. A PolarDB table occupies two files. A partition table occupies N + 2 files, where N indicates the number of partitions. The following error message appears when you create a table after the maximum number of files is reached: 
    ERROR 3017 (HY000): Too many files. PolarDB only supports 2048 files every 10GB disk size. Please drop some tables/databases before creating new tables

    In this case, you need to delete some tables or upgrade the specifications of your cluster.

  • The maximum number of connections.

    In the preceding table, the number of connections refers to the number of connections for an individual node. It does not refer to the total number of connections in a cluster.

Table 1. Other limits
Operation Limit
Table name The name of a table in a cluster of any specification must be up to 64 characters and digits or 50 Chinese characters in length.
Serializable isolation level Not supported

FAQ

  • Compared with native MySQL, what is the upper limit of the storage for each PolarDB table?

    The size of a single table is unlimited in PolarDB. However, the size of a table depends on the size of the disk space.

  • Can I create 10,000 databases in a PolarDB cluster? What is the upper limit for the number of databases?

    PolarDB allows you to create 10,000 databases. The maximum number of tables for a PolarDB cluster depends on the number of files.

  • Does the number of read-only nodes depend on the maximum number of connections? Can I increase the maximum number of connections by adding read-only nodes?

    No, the number of read-only nodes does not depend on the maximum number of connections. The maximum number of connections for PolarDB depends on the node specifications. To increase the maximum number of connections, upgrade the specifications. For more information, see Upgrade specifications.