Supabase Backend as a Service · 课时

高级地理空间数据（PostGIS）

集成 PostGIS 以处理复杂的地理空间数据、执行基于位置的查询，并在应用中构建地图功能

高级地理空间数据（PostGIS） 是 CoddyKit 上的免费 Supabase Backend as a Service 课时。这是第 2 节课，共 3 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 Supabase Backend as a Service 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Supabase Backend as a Service 课程共包含 3 节课。

本课时的部分内容尚未翻译，以英文显示。

Unlocking Geospatial Power

Welcome to Advanced Geospatial Data (PostGIS)! In this lesson, we'll explore how to handle location-based data directly within your Supabase database.

Geospatial data is crucial for apps that deal with maps, locations, navigation, or proximity services.

What is PostGIS?

PostGIS is a powerful, open-source extension for PostgreSQL that adds support for geographic objects.

It transforms your database into a spatial database.
It allows you to store, query, and analyze location data (points, lines, polygons).
Supabase, being built on PostgreSQL, fully supports PostGIS.

Why Use PostGIS?

Traditional databases store locations as separate latitude/longitude columns, making complex queries difficult.

PostGIS provides specialized functions to:

Calculate distances between points.
Find locations within a specific radius.
Determine if points are inside an area.
Perform complex spatial joins and analyses.

Enabling PostGIS Extension

Before using PostGIS, you need to enable the extension in your Supabase project. This is a one-time step done via the SQL Editor in your Supabase dashboard.

Simply run the following command:

CREATE EXTENSION IF NOT EXISTS postgis;

Geospatial Data Types

PostGIS introduces new data types to store spatial information:

GEOMETRY: Stores data on a 2D Cartesian plane (flat earth model). Good for small-scale, local areas.
GEOGRAPHY: Stores data on a spherical globe (real-world coordinates). Best for large-scale, global applications.

We'll primarily use GEOMETRY for simplicity in examples, but GEOGRAPHY is often preferred for real-world distances.

Creating a Table with Spatial Data

Let's create a table to store points of interest, like coffee shops, using a GEOMETRY column. The SRID (Spatial Reference ID) 4326 is standard for latitude/longitude.

CREATE TABLE coffee_shops (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  name TEXT NOT NULL,
  location GEOMETRY(Point, 4326)
);

Inserting Geospatial Points

To insert a point, we use the ST_GeomFromText() function, which converts a Well-Known Text (WKT) representation into a PostGIS geometry object. The format is 'POINT(longitude latitude)'.

INSERT INTO coffee_shops (name, location) VALUES
('Espresso Hub', ST_GeomFromText('POINT(-0.1278 51.5074)', 4326)),
('Bean Scene', ST_GeomFromText('POINT(-0.1419 51.5085)', 4326)),
('Daily Grind', ST_GeomFromText('POINT(-0.1000 51.5200)', 4326));

Finding Nearest Locations

One common task is finding locations near a specific point. We can use ST_Distance() to calculate the distance between two geometry points. The unit of distance depends on the SRID (e.g., meters for 4326 on GEOGRAPHY type, degrees for GEOMETRY type).

Here, we find shops near a reference point (e.g., user's current location).

SELECT
  name,
  ST_Distance(
    location,
    ST_GeomFromText('POINT(-0.1300 51.5090)', 4326)
  ) AS distance_in_degrees
FROM
  coffee_shops
ORDER BY
  distance_in_degrees
LIMIT 1;

Efficient Proximity Search

For more efficient proximity searches, especially when working with GEOGRAPHY types for real-world distances, ST_DWithin() is excellent. It checks if two geometries are within a specified distance.

Let's find all coffee shops within 1000 meters of a specific point using GEOGRAPHY for accurate distance calculation.

SELECT
  name
FROM
  coffee_shops
WHERE
  ST_DWithin(
    location::geography,
    ST_GeomFromText('POINT(-0.1300 51.5090)', 4326)::geography,
    1000 -- 1000 meters
  );

PostGIS Query Check

You've learned how to enable PostGIS, create tables with spatial columns, and insert/query geospatial data.

Which PostGIS function would you typically use to find all points of interest that are located within 500 meters of a user's current position, assuming you're using the GEOGRAPHY type?

Recap: Geospatial Data

Great job! You've taken your first steps into the world of geospatial data with PostGIS and Supabase.

We enabled the PostGIS extension.
Learned about GEOMETRY and GEOGRAPHY types.
Created tables and inserted data using WKT.
Performed basic spatial queries like distance calculation and proximity searches with ST_Distance() and ST_DWithin().

PostGIS opens up a vast array of possibilities for location-aware applications!

常见问题解答

「高级地理空间数据（PostGIS）」课时是免费的吗？

是的 — 「高级地理空间数据（PostGIS）」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Supabase Backend as a Service 课程的其余内容，请升级到 CoddyKit PRO。 Supabase Backend as a Service 课程共包含 3 节课。

「高级地理空间数据（PostGIS）」这节课中我会学到什么？

集成 PostGIS 以处理复杂的地理空间数据、执行基于位置的查询，并在应用中构建地图功能你通过在浏览器中直接运行的动手代码来练习 Supabase Backend as a Service，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 Supabase Backend as a Service 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Supabase Backend as a Service 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。这是第 2 节课，共 3 节。

「高级地理空间数据（PostGIS）」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 Supabase Backend as a Service 课中编写并运行代码吗？

能。每节 Supabase Backend as a Service 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

此课程中的所有课时

← 返回 Supabase Backend as a Service