Key Concepts
Last updated: 2025-04-24 17:12:00
This document will introduce the key concepts of using the TencentDB for CTSDB 3.0 to help you better understand the product capabilities. For more information, see InfluxDB v1.7 Official Documentation.
DataBase
The concept of database is included in CTSDB 3.0. Users can create a database through the create database xxx command.
Point
A point consists of time, field, and tags, equivalent to a row of data in a traditional database.
Measurement
In CTSDB 3.0, a measurement refers to the metric name of the measured time series data, and the measurement results are calculated on the time scale. For example, cpu_usage indicates the CPU utilization. It can be understood as a database table.
Aggregation
In CTSDB 3.0, aggregation refers to the process of combining multiple data points into a single data point, usually applied to perform statistical analysis on data, such as calculating the average value, maximum value, minimum value, or sum value. Aggregation can also be applied to combinations of multiple measurements or tags, such as calculating the average value of an entire measurement, or calculating the sum value of a specific tag value. Aggregation can help you better understand data and extract useful information.
Typically, aggregation is used together with query. You can use InfluxQL to specify the data to be aggregated, the aggregate function, and the time range. For example, the SQL statement for querying the average value of all data points with the tag "server1" in the measurement "cpu" is
SELECT MEAN("usage_idle") FROM "cpu" WHERE "server" = 'server1' AND time >= now() - 1h.Retention Policy (RP)
RP is a storage policy used to set the retention time of data. Each database will automatically create a default storage policy at first, with the data retention time set to permanent. Later, users can set it themselves, such as retaining the data of the last 2 hours. If no storage policy is specified when you insert and query data, the default storage policy will be used and can be modified. CTSDB 3.0 will periodically clear the expired data.
Continuous Query (CQ)
In CTSDB 3.0, a CQ is an automatically executed query that periodically queries a group of measurements and writes the results into another measurement. It is usually used for data aggregation, compression, or statistics to achieve better management and analysis.
Series
In CTSDB 3.0, a series is a unique data collection composed of a measurement and a group of tags. It is the basic unit for query and aggregation. When you perform a query, you can specify the measurement, tags, and time range to be queried to return data points of one or more series. You can also use InfluxQL to aggregate series and calculate the average value and sum value of each series, or collect other statistical information.
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