MySql spatial index implementation

What is spatial index

Spatial index is a data structure specially used to optimize geospatial data queries. It accelerates the search speed of spatial objects such as points, lines, and surfaces by organizing and storing geometric properties of spatial data. In MySQL, spatial indexing is mainly implemented based on R-Tree (recursive tree) data structure.

In MySQL, directly use geometric data types (e.g.POINT, LINESTRING, POLYGONetc.) The concept of using "geometric index" is not completely accurate, because MySQL does not directly provide an index type named "geometric index". However, you can create a Spatial Index for these geometric data types, which allows you to efficiently query and manipulate spatial data.

MySQL's spatial data types and spatial functions areSPATIALDefined in extensions, these extensions are mainly used to process geospatial data. MySQL usageR-treeThe data structure stores spatial indexes to support the rapid search of spatial data.

Here are the steps to create a spatial index for geometric data types in MySQL:

Define the space column:

First, you need to define one or more spatial columns in the table. This can be usedSPATIALData type (such asPOINT, LINESTRING, POLYGONetc.) to complete.

CREATE TABLE geo_table (  
    id INT AUTO_INCREMENT PRIMARY KEY,  
    name VARCHAR(255),  
    location POINT SPATIAL NOT NULL,  
    SPATIAL INDEX(location)  
);

Note: In the example above,SPATIAL INDEX(location)A spatial index was created. However, in MySQL 5.7 and earlier, you may need to create a spatial index separately after the table definition, as follows:

CREATE SPATIAL INDEX idx_location ON geo_table(location);

Insert spatial data:

You can useGeomFromText()orPointFromText()Wait for functions to insert spatial data.

INSERT INTO geo_table (name, location)  
VALUES ('Location 1', GeomFromText('POINT(10 20)'));

Perform a space query:

Space functions using MySQL (such asST_Distance_Sphere(), ST_Within(), MBRContains(), MBRIntersects()etc.) to perform spatial query.

For example, find a distance given point(10, 20)All locations within a certain distance:

SELECT * FROM geo_table  
WHERE ST_Distance_Sphere(location, GeomFromText('POINT(10 20)')) < 100; -- Assume the distance is 100 rice（Notice：The unit of distance depends on the coordinate system and Earth model you use）

Optimization and maintenance:

Like other types of indexes, spatial indexes require regular optimization and maintenance to ensure performance. You can useOPTIMIZE TABLECommands to optimize tables and useANALYZE TABLECommand to update the table's statistics. However, be aware that these commands may not have a direct impact on spatial indexes, as they are mainly used to process physical storage and statistics of tables.

Notes:

When using spatial data types and functions, make sure you understand their limitations and performance characteristics. For example, spatial indexes may increase the overhead of insertion, update, and delete operations because they require maintenance of additional index structures. In addition, the performance of spatial queries may be affected by factors such as data distribution, index design, and query complexity. Therefore, when designing and using spatial databases, be sure to conduct adequate testing and evaluation.

Actual case analysis

1. Case 1: Location query in the map application

Suppose we have a map application that needs to quickly query nearby points of interest. We can create a table with geolocation information and create a spatial index for the table.

CREATE TABLE points_of_interest (
    id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(255),
    location POINT NOT NULL,
    SPATIAL INDEX idx_location (location)
);

When we need to query the point of interest closest to a certain point, we can use the following query:

SELECT * FROM points_of_interest 
ORDER BY ST_Distance_Sphere(location, PointFromText('POINT(10 10)')) 
LIMIT 10;

2. Case 2: Delivery point in logistics distribution

Suppose we have a logistics company that needs to manage a large amount of goods delivery information. Each delivery point has a geographical location (latitude and longitude coordinate). We need to quickly find the nearest delivery point based on the customer's geographical location.

CREATE TABLE delivery_points (
    id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(255),
    location POINT NOT NULL,
    SPATIAL INDEX idx_location (location)
);

When we need to query the delivery point closest to a customer, we can use the following query:

SELECT * FROM delivery_points 
ORDER BY ST_Distance_Sphere(location, PointFromText('POINT(10 10)')) 
LIMIT 1;

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