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System Limits
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This topic does not apply to MemSQL Helios.
This topic specifies maximum sizes and numbers of various MemSQL components. Use the following links to navigate to a section below:
Cluster-Level Limits
| Item | Max Spec (enforced) | Max Spec (recommended) | Comments |
|---|---|---|---|
| Number of hosts in a cluster | None | Workloads that generate significant network traffic between hosts should be limited to clusters with smaller number of hosts. | |
| Number of nodes in a cluster (includes leaves and aggregators) | None | Workloads that generate significant network traffic between nodes should be limited to clusters with smaller number of nodes. | |
| Number of databases in a cluster | None | Each database requires memory for transaction buffer and more databases implies greater demand on available memory. | |
| Concurrent queries in a cluster | None | Each aggregator will only actually execute a limited number of queries at once (defined by max_connection_threads, default 192). Beyond that concurrency, queries will be queued up. | |
| Simultaneous client connections | 100,000 per aggregator | For more information, read about max_connections |
Database-Level Limits
| Item | Max Spec (enforced) | Max Spec (recommended) | Comments |
|---|---|---|---|
| Number of tables in a database | Each table costs some per-table memory overhead. | ||
| Number of partitions in a cluster | None |
Table-Level Limits
| Item | Max Spec (enforced) | Max Spec (recommended) | Comments |
|---|---|---|---|
| Number of columns per table | 4096 | ||
| Row size in bytes | 64KB | Limit does not apply to variable-length strings such as VARCHAR, VARBINARY, TEXT, etc. | |
| Length of names in characters (applies to table names, column names) | 64 | ||
| Number of indexes per table | 63 | ||
| Number of columns per index | 32 | ||
| Number of tables in a join for each SELECT | 253 |
Naming Constraints
| Item | Constraints |
|---|---|
| Names | Database names only allow alphanumeric characters and cannot start with a digit. Table names can contain both alphanumeric and non-alphanumeric characters. |
| User names | Maximum length of 32 characters. |
| Role names | No length limit. |
| Group names | No length limit. |
