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Database Limits
This section lists the limits that are applied to database objects in Yellowbrick databases.
| Database Limit | Value | Notes |
|---|---|---|
| Databases per appliance | 1,000 | The maximum number of databases includes the yellowbrick database, so the effective limit is 999 user-created databases. |
| Tables per appliance | 70,000 | There is no limit on the number of tables per database, only a limit on the total number per appliance. This limit applies to persistent tables only. |
| Size of internal temporary tables | 30MB | Temporary tables that the system creates during queries are limited to a size of 30MB. This limitation does not apply to temporary tables created by users. |
| Columns per table | 1600 | |
| Rows per table | 264 | |
| Width of a row in a column | 64256 bytes | A single row can be 256 bytes longer than any single VARCHAR column. |
Length of a VARCHAR column | 64000 bytes | For other data type limits, see SQL Data Types. |
| Length of database object names | 128 bytes | See SQL Identifiers. |
| Number of distribution columns per table | 1 | See Distribution Options. |
| Number of sort columns per table | 1 | See Sorted and Clustered Tables. |
| Number of cluster columns per table | 4 | See Sorted and Clustered Tables. |
| Number of partition columns per table | 4 | See Partitioning Options. |
Maximum number of IN list items | 200000 | See IN. |
Maximum number of WHEN clauses in a CASE expression | 8192 | |
| Maximum number of ACLs per database object | 1000 (default) | The number of privileges you can grant to a database object defaults to 1000 but can be increased to a maximum of 5000. |
User connection/session limits (max_user_connections) | 2000 | The maximum number of database user connections is 2000. (The related max_connections value is 2300, which allows for 300 additional system user connections; max_user_connections must be set to a lower value than max_connections.) See also Managing Idle Sessions. |
| Replicas per database | 1 | See Database Replication. |
Practical Limits for Tables and Partitions
Yellowbrick does not enforce limits on either the number of tables per database or the number of partitions per table. The maximum number of tables is 70,000 per appliance, regardless of the number of databases you create. Ideally, the number of partitions created per table should be less than 1,000. (See Partitioning Tables for details about how the actual number of partitions is computed, based on the partitioning columns you define. The enforced maximum is approximately 250,000 partitions.)
Respecting these more practical limits will help to optimize the storage system and improve both query performance and the efficiency of background database operations. In addition to monitoring the number of tables and partitions on your system, try to avoid rapid loading of a large number of small tables with a few rows at a time. When many thousands of small write transactions are committed to the database, fragmentation of the storage media is likely to occur.
Parent topic:Database Administration