Use constraints and recommendations
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To keep your cluster stable and performant, stay within the limits listed below. Exceeding these values can degrade query performance, destabilize the system, and increase the risk of crashes or service interruptions.
If you need to exceed a recommended maximum value, join the Hologres DingTalk group for technical support. See Get support for Hologres.
| Item | Recommended maximum |
|---|---|
| Databases per instance | 10 |
| Instance purchases, scale-outs, or scale-ins per day | 10 |
| Accounts per instance (Alibaba Cloud accounts, RAM users, and custom accounts) | 256. See Manage users. |
| Connections per instance | Varies by instance type. See Instance types. |
| Tables per table group (including child partitioned tables, excluding foreign tables) | 10,000. To check the current table count per table group, run: SELECT property_value, count(1) FROM hologres.hg_table_properties WHERE property_key = 'table_group' GROUP BY 1; |
| Columns per column-oriented table | 300 |
| Columns per row-oriented table | 3,000 |
| Columns per row-column hybrid table | 300 |
| Total columns across all tables in a table group | 1,000,000 |
| Table comment length | 1,024 characters |
| Column comment length | 1,024 characters |
| Maximum value size (TEXT, CHAR, VARCHAR, JSON, JSONB, BLOB, BYTEA, BIT, VARBIT) | 4 MB |
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