How the IsSimple() function works in Mariadb?

The MariaDB IsSimple() function is used to verify that a given geometry does not have any anomalous geometric points, such as self-intersections or complex loops. It is an essential function for ensuring the integrity of geometric data in spatial databases.

Syntax

The syntax for the MariaDB IsSimple() function is as follows:

IsSimple(g)

or

ST_IsSimple(g)

Where g is the geometry to be tested. The function returns true if the geometry is simple, false if it is not, or NULL if the geometry is NULL.

Examples

Example 1: Simple LineString

This example demonstrates checking the simplicity of a LineString.

SELECT IsSimple(ST_GeomFromText('LINESTRING(0 0, 1 1, 2 2)'));

The output for this statement is:

+--------------------------------------------------------+
| IsSimple(ST_GeomFromText('LINESTRING(0 0, 1 1, 2 2)')) |
+--------------------------------------------------------+
|                                                      1 |
+--------------------------------------------------------+

This indicates that the LineString does not intersect itself and is considered simple.

Example 2: Non-Simple LineString

Here, we check a LineString that intersects itself.

SELECT IsSimple(ST_GeomFromText('LINESTRING(0 0, 2 2, 1 1, 3 3)'));

The output for this statement is:

+-------------------------------------------------------------+
| IsSimple(ST_GeomFromText('LINESTRING(0 0, 2 2, 1 1, 3 3)')) |
+-------------------------------------------------------------+
|                                                           0 |
+-------------------------------------------------------------+

This result confirms that the LineString is not simple due to self-intersection.

Example 3: Simple Polygon

To demonstrate IsSimple() with a Polygon, we’ll create a simple Polygon without self-intersections.

SELECT IsSimple(ST_GeomFromText('POLYGON((0 0, 1 0, 1 1, 0 1, 0 0))'));

The output for this statement is:

+-----------------------------------------------------------------+
| IsSimple(ST_GeomFromText('POLYGON((0 0, 1 0, 1 1, 0 1, 0 0))')) |
+-----------------------------------------------------------------+
|                                                               1 |
+-----------------------------------------------------------------+

This shows that the Polygon is simple and does not intersect itself.

Example 4: Complex Polygon

This example checks a Polygon that intersects itself.

SELECT IsSimple(ST_GeomFromText('POLYGON((0 0, 1 1, 1 0, 0 1, 0 0))'));

The output for this statement is:

+-----------------------------------------------------------------+
| IsSimple(ST_GeomFromText('POLYGON((0 0, 1 1, 1 0, 0 1, 0 0))')) |
+-----------------------------------------------------------------+
|                                                               0 |
+-----------------------------------------------------------------+

This confirms that the Polygon is not simple due to self-intersection.

Example 5: Using IsSimple() with a MultiLineString

IsSimple() can also be used to check the simplicity of a MultiLineString.

SELECT IsSimple(ST_GeomFromText('MULTILINESTRING((0 0, 1 1),(2 2, 3 3))'));

The output for this statement is:

+---------------------------------------------------------------------+
| IsSimple(ST_GeomFromText('MULTILINESTRING((0 0, 1 1),(2 2, 3 3))')) |
+---------------------------------------------------------------------+
|                                                                   1 |
+---------------------------------------------------------------------+

This indicates that the MultiLineString is simple as there are no self-intersections.

Related Functions

Below are a few functions related to MariaDB IsSimple():

• MariaDB ST_Overlaps() function is used to determine if two geometries share space as a surface.
• MariaDB ST_Intersects() function is used to determine if two geometries intersect at any point.
• MariaDB ST_Touches() function is used to determine if two geometries have common boundaries but do not overlap.

Conclusion

The IsSimple() function is a vital tool for working with spatial data in MariaDB. It allows developers to ensure that geometries are free of complexities that could affect spatial queries and operations. By using IsSimple() and related functions, one can maintain the integrity of spatial data and perform accurate spatial analysis. Understanding and utilizing these functions effectively is key to managing and analyzing spatial data in MariaDB.