Limits

This topic describes the limits of PolarDB for MySQL.

Edition	Node instance type CPU and memory	Memory for a file system	Maximum number of files	Maximum connections
Cluster Edition (Dedicated)	polar.mysql.x4.medium 2 cores, 8 GB memory	800 MB	1,024,000	6,000
	polar.mysql.x4.large 4 cores, 16 GB memory	1,300 MB	2,048,000	8,000
	polar.mysql.x4.xlarge 8 cores, 32 GB memory	2,400 MB	4,096,000	10,000
	polar.mysql.x8.xlarge 8 cores, 64 GB memory	3,500 MB	6,144,000	16,000
	polar.mysql.x8.2xlarge 16 cores, 128 GB memory	10,240 MB	20,480,000	32,000
	polar.mysql.x8.4xlarge 32 cores, 256 GB memory	10,240 MB	20,480,000	64,000
	polar.mysql.x8.8xlarge 64 cores, 512 GB memory	10,240 MB	20,480,000	64,000
	polar.mysql.x8.12xlarge 88 cores, 710 GB memory	10,240 MB	20,480,000	100,000
Cluster Edition (General-purpose)	polar.mysql.g2.medium 2 cores, 4 GB memory	800 MB	1,024,000	1,800
	polar.mysql.g4.medium 2 cores, 8 GB memory	800 MB	1,024,000	2,000
	polar.mysql.g2.large 4 cores, 8 GB memory	1,300 MB	2,048,000	3,000
	polar.mysql.g4.large 4 cores, 16 GB memory	1,300 MB	2,048,000	6,000
	polar.mysql.g2.xlarge 8 cores, 16 GB memory	1,300 MB	2,048,000	6,000
	polar.mysql.g4.xlarge 8 cores, 32 GB memory	2,400 MB	4,096,000	10,000
	polar.mysql.g4.2xlarge 16 cores, 64 GB memory	3,500 MB	6,144,000	16,000
	polar.mysql.g4.4xlarge 32 cores, 128 GB memory	10,240 MB	20,480,000	32,000

The preceding table describes the limits of PolarDB for MySQL on the following metrics:

Memory for a file system
This metric refers to 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 amount of consumed 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 regular PolarDB table occupies two files. However, in the case of a partitioned table, the number of files occupied is N + 2, where N represents 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 must delete some tables or upgrade your cluster.
Maximum 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.

Other limits

Item	Limits
Table name	The name of a table in a cluster can be up to 64 letters and digits or 50 Chinese characters in length.
Serializable isolation level	Serializable isolation is not supported.

FAQ

Can I create 10,000 databases in PolarDB? What is the maximum number of databases in PolarDB?
Yes, you can create 10,000 databases in PolarDB. PolarDB does not impose a limit on the number of databases within a cluster. However, the number of databases can be constrained by the specifications of the cluster and the maximum number of files.
What is the maximum size of data that a single table can store in PolarDB compared with native MySQL?
PolarDB does not impose a limit on the size of a single table. However, the size of a table is constrained by the available disk space.
Does the maximum number of connections depend on the number of read-only nodes? Can I increase the maximum number of connections by adding read-only nodes?
No, the maximum number of connections does not depend on the number of read-only nodes. The maximum number of connections for a PolarDB cluster is determined by the node specifications. To increase the maximum number of connections, you can upgrade the cluster. For more information, see Manually upgrade or downgrade a PolarDB cluster.