Help Center/ GeminiDB/ GeminiDB Cassandra API/ Service Overview/ Database Constraints/ Database Usage
Updated on 2024-08-03 GMT+08:00
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Database Usage

Mandatory Constraints

General rules

  • If the size of a request or any configuration value in it exceeds the preset alarm threshold, the client receives a warning and Cloud Eye generates an alarm. For some requests, events are also generated.
  • If the size of a request or any configuration value in it exceeds the preset failure threshold, the request fails and an event is generated.

Specific constraints

  • Data volume of a single table row:
    • When a database reads data, it will combine multiple writes of the same primary key into one row. When the amount of data in a single row exceeds the preset threshold, an alarm and event are generated.
  • A single partition:
    • The database background scanning task periodically collects partitions, rows in a partition, and total size of all rows in a partition. When the amount of data in a single row exceeds the preset threshold, an alarm and event are generated.
  • Number of elements of the collection type:
    • When your database reads data (of the types like Map, List, Set, and Tuple) in the collection column, the database will count all elements in the column. An alarm and event is generated when the number of elements exceeds the preset threshold.
  • Amount of data returned by a query:
    • Before a response is returned to the client, the database checks the amount of data in the response. If the amount exceeds the preset threshold, an alarm is generated or the request fails.
  • Number of tombstones returned by a query:
    • After a query request is submitted, the database checks the number of tombstones scanned. When the number exceeds the preset threshold, an alarm is generated or the request fails.
Table 1 Thresholds for GeminiDB Cassandra constraints

Constraint

Alarm Threshold

Failure Threshold

Amount of data in a single row

100KB

-

A single partition
  • Rows: 100,000
  • Size: 100 MB.

-

Number of elements of the collection type

500

-

Amount of data returned by a query

2MB

100MB

Number of tombstones returned by a query

1,000

100,000

Optional Constraints

  • Do not use ALLOW FILTERING:
    • A warning is returned when the ALLOW FILTERING statement is executed.
  • Use a proper limit value for a RANGE query:
    • Using a proper limit for prefetching can accelerate RANGE queries. You can check whether a limit value is proper based on the average limit values of all monitoring items.
Parent topic: Database Constraints