Скачать или смотреть Understanding the Use of Postgres Table Inheritance in Database Design

Explore the benefits and use cases of `Postgres table inheritance` compared to partitioning, and uncover how to effectively structure your database.
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Exploring the Use of PostgreSQL Table Inheritance

When designing databases, especially in applications like data management, it’s essential to understand the various options for organizing your data. One such feature offered by PostgreSQL is table inheritance. A common question arises: If PostgreSQL also supports partitioned tables, what is the purpose of child tables through inheritance? In this post, we will break down both concepts and clarify when to use one over the other.

The Problem: Table Inheritance vs. Partitioned Tables

Consider an example where we have a users table with a created_date column. There are typically two approaches to manage this data effectively:

Create numerous child tables of the users table, distributing user data based on created_date — for example, one table for each date (e.g., user_jan01_21).

Implement a partitioned table utilizing created_date as the partitioning key.

Both methods have their advantages, but they also serve different purposes. The key question here is: What problem does table inheritance solve that partitioning cannot?

Understanding the Differences

1. Advantages of Declarative Partitioning

When aiming for simplicity and performance, declarative partitioning is generally superior. This method provides significant ease of use along with enhanced performance and additional features. For instance:

Automatic data management: PostgreSQL handles data distribution across partitions more efficiently.

Optimized queries: Queries can automatically leverage partitioning rules to improve performance.

2. Unique Features of Table Inheritance

While partitioning is advantageous for specific scenarios, table inheritance also offers unique features that partitioning doesn’t provide:

Additional Columns: Child tables can have their own unique columns that are not present in the parent table. This can allow for greater flexibility in data modeling.

Multiple Parent Tables: A table can inherit from more than one parent table, enabling complex relationships and hierarchies in the data structure.

3. Query Behavior with Table Inheritance

One practical aspect of using table inheritance is how queries are executed. When you select from the parent table, you will automatically fetch data from all child tables, behaving like an UNION ALL operation. For example, consider the following query:

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In this query, without the ONLY keyword, all relevant child tables will be scanned along with the parent, providing a comprehensive view of the data across all dates collected.

Conclusion

In summary, while both PostgreSQL table inheritance and partitioned tables serve to manage large datasets effectively, they cater to different needs within a database architecture. Choose partitioning for streamlined performance and simplicity when organizing large datasets. On the other hand, consider using table inheritance for greater flexibility, particularly when your data structure requires additional attributes or complex relational hierarchies.

This understanding will help you make informed decisions about your database design, ensuring efficiency and effectiveness as your data grows.

By evaluating these differences, you can tailor the data architecture to better suit your needs, enhancing both functionality and maintainability.