This page defines the core concepts used in ApsaraDB for SelectDB.
Quick reference
| Term | What it is |
|---|---|
| Region | Geographical location where your resources reside |
| Zone | Isolated physical area within a region |
| Instance | A unit that provides computing, storage, and network resources |
| Cluster | A compute unit within an instance; compute-storage separation |
| Storage | Shared storage layer backed by OSS |
| Catalog | A collection of databases; internal or external |
| Database | A named container of tables, views, functions, and data types |
| Table | Structured data stored in rows and columns |
| Index | A structure that speeds up data filtering and queries |
| View | A virtual table derived from one or more base tables |
| Function | A built-in or custom routine for querying and calculating data |
Region
A region is the geographical location where ApsaraDB for SelectDB resources reside. Specify a region when you purchase resources. The region cannot be changed after resources are created.
Zone
A zone is a physical area within a region with an independent power supply and network. Zones within the same region are isolated from each other but can communicate over an internal network. Network latency between instances in the same zone is lower than between instances in different zones.
Instance
An instance provides the computing, storage, and network resources for ApsaraDB for SelectDB. Resources are isolated between instances.
Cluster
A cluster is the compute unit within an ApsaraDB for SelectDB instance. ApsaraDB for SelectDB uses a compute-storage separation architecture, which allows multiple compute clusters to share the same stored data within an instance.
Each cluster provides computing resources (vCPUs and memory) and cache resources. Computing capacity is isolated between clusters, so you can configure different clusters to meet the performance and workload requirements of different services.
ApsaraDB for SelectDB storage
ApsaraDB for SelectDB uses a compute-storage separation architecture. Multiple compute clusters share stored data within an instance, which reduces the number of data replicas needed. Storage is backed by Object Storage Service (OSS), which significantly lowers storage costs.
Catalog
A catalog is a collection of databases. ApsaraDB for SelectDB has two catalog types:
Internal catalog — Contains the internal databases of ApsaraDB for SelectDB.
External catalogs — Connect to external data sources such as Hive, Iceberg, and Hudi for queries.
Database
A database belongs to a catalog and contains tables, columns, views, functions, and data types.
Table
A table belongs to a database and stores structured data as rows and columns. Each row represents a record; each column represents a field.
ApsaraDB for SelectDB supports the following data models:
Aggregate key model
Unique key model
Duplicate key model
Index
An index sorts the values of one or more columns to speed up data filtering and query execution. ApsaraDB for SelectDB provides two categories of indexes:
Built-in intelligent indexes — Created and maintained automatically by the system:
Zone map indexes
Prefix indexes
Custom secondary indexes — Created manually to accelerate specific query patterns:
Inverted indexes
Bitmap indexes
Bloom filter indexes
View
A view is a virtual table derived from one or more base tables or views.
ApsaraDB for SelectDB automatically maintains the data in materialized views to keep them consistent with their base tables whenever data is imported or deleted. When you run a query, the system automatically matches the most suitable materialized view and reads data from it. There is no additional charge for maintaining materialized views.
Function
Functions query, aggregate, and calculate data stored in databases. They can be used in SQL statements or defined as custom SQL functions.
ApsaraDB for SelectDB supports the following function types:
| Type | Purpose | Examples |
|---|---|---|
| Aggregate functions | Calculate a value across a set of rows and return a single result. | SUM, AVG, COUNT, MAX, MIN |
| String functions | Process and transform string data: concatenation, truncation, replacement, and case conversion. | SUBSTRING, CONCAT, REPLACE, UPPER, LOWER |
| Mathematical functions | Perform numeric calculations. | ABS, CEIL, FLOOR, ROUND |
| Date and time functions | Format, calculate, and add or subtract date and time values. | NOW, DATE_FORMAT, DATEDIFF, DATE_ADD |
| Conditional functions | Return different results based on evaluated conditions. | IF, CASE |