PolarDB for MySQL enforces resource limits based on node specifications, along with a set of fixed constraints. Use this page to plan cluster sizing, avoid file or connection errors, and understand unsupported features before you encounter them in production.
Resource limits by node specification
Connection limits apply per node, not per cluster. Adding read-only nodes does not increase the connection limit for any individual node. To increase connections, change the cluster specifications.
Cluster Edition (Dedicated)
| Node type | CPU and memory | File system memory | Max files | Max connections |
|---|---|---|---|---|
| polar.mysql.x4.medium | 2 cores, 8 GB | 800 MB | 1,024,000 | 6,000 |
| polar.mysql.x4.large | 4 cores, 16 GB | 1,300 MB | 2,048,000 | 8,000 |
| polar.mysql.x4.xlarge | 8 cores, 32 GB | 2,400 MB | 4,096,000 | 10,000 |
| polar.mysql.x8.xlarge | 8 cores, 64 GB | 3,500 MB | 6,144,000 | 16,000 |
| polar.mysql.x8.2xlarge | 16 cores, 128 GB | 10,240 MB | 20,480,000 | 32,000 |
| polar.mysql.x8.4xlarge | 32 cores, 256 GB | 10,240 MB | 20,480,000 | 64,000 |
| polar.mysql.x8.8xlarge | 64 cores, 512 GB | 10,240 MB | 20,480,000 | 64,000 |
| polar.mysql.x8.12xlarge | 88 cores, 710 GB | 10,240 MB | 20,480,000 | 100,000 |
Cluster Edition (General-purpose)
| Node type | CPU and memory | File system memory | Max files | Max connections |
|---|---|---|---|---|
| polar.mysql.g2.medium | 2 cores, 4 GB | 800 MB | 1,024,000 | 1,800 |
| polar.mysql.g4.medium | 2 cores, 8 GB | 800 MB | 1,024,000 | 2,000 |
| polar.mysql.g2.large | 4 cores, 8 GB | 1,300 MB | 2,048,000 | 3,000 |
| polar.mysql.g4.large | 4 cores, 16 GB | 1,300 MB | 2,048,000 | 6,000 |
| polar.mysql.g2.xlarge | 8 cores, 16 GB | 1,300 MB | 2,048,000 | 6,000 |
| polar.mysql.g4.xlarge | 8 cores, 32 GB | 2,400 MB | 4,096,000 | 10,000 |
| polar.mysql.g4.2xlarge | 16 cores, 64 GB | 3,500 MB | 6,144,000 | 16,000 |
| polar.mysql.g4.4xlarge | 32 cores, 128 GB | 10,240 MB | 20,480,000 | 32,000 |
Column definitions:
File system memory: The memory the file system uses when the cluster reaches its storage limit during normal read and write operations. Normal operations exclude stress testing and Data Definition Language (DDL) operations on large tables. If the cluster has not reached its storage limit, actual file system memory usage is lower than this value.
Max files: The total count across user files, database system files (approximately 100), and log files. Run
SHOW POLAR LOGSto check the current log file count. A non-partitioned table uses one file; a partitioned table uses N+1 files, where N is the number of partitions. If you reach the file limit, the following error is returned:ERROR 3017 (HY000): Too many files. PolarDB only supports 2048 files every 10GB disk size. Please drop some tables/databases before creating new tablesTo resolve this, drop unused tables or upgrade the cluster specifications.
Max connections: Applies to a single node. See the note above for how to increase this limit.
Storage and naming limits
| Category | Limit | Adjustable |
|---|---|---|
| Maximum data volume per table | 64 TB | No |
| Maximum number of databases | 10,000 (no hard limit; actual maximum depends on cluster specifications and max files) | Yes — upgrade specifications to increase the effective limit |
| Maximum number of tables per database | No hard limit (consistent with MySQL behavior); InnoDB supports up to 4 billion tables, but available storage determines the practical limit | Yes — upgrade specifications to increase storage |
| Table name length | Up to 64 letters and digits, or 50 Chinese characters | No |
A 10 GB disk provides a maximum of 2,048 inodes, and each inode corresponds to one file. The number of tables a cluster can hold is ultimately constrained by this file limit. A non-partitioned table uses one file; a partitioned table uses N+1 files, where N is the number of partitions.
Unsupported features
| Feature | Status |
|---|---|
| Serializable isolation level | Not supported |
| Superusers | Not supported |
FAQ
Does adding read-only nodes increase the connection limit?
No. The connection limit is determined by node specifications, not by the number of read-only nodes. To increase the limit, change the cluster specifications.
Does PolarDB support superusers?
No. Superusers are not supported.