Bug #64653 ST_Contains() reports that a polygon does not contain itself

• Submitted: 15 Mar 2012 1:19
• Modified: 5 Oct 2012 17:04
• Reporter: Benjamin Morel
• Status: Closed
• Category: MySQL Server: GIS
• Severity: S3 (Non-critical)
• Version: 5.6.4 m7, 5.6.5 m8
• OS: Any
• CPU Architecture: Any
• Tags: Geometry, gis, polygon, spatial, ST_Contains

[15 Mar 2012 1:19] Benjamin Morel

Description:
This bug has probably the same roots as the following bug:
http://bugs.mysql.com/bug.php?id=64649

In the example below, we're checking whether a polygon contains itself. PostGIS reports true, MySQL reports false.

How to repeat:
SET @a = ST_GeomFromText('POLYGON((0 0, 1 0, 1 1, 0 1, 0 0))', 4326);
SELECT ST_Contains(@a, @a);

Expected result: 1
Actual result: 0

[15 Mar 2012 7:55] Valeriy Kravchuk

Thank you for the bug report. Verified with current mysql-trunk also:

[openxs@chief trunk]$ bin/mysql -uroot test
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.6.5-m8-debug Source distribution

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Oracle is a registered trademark of Oracle Corporation and/or its
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Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> SET @a = ST_GeomFromText('POLYGON((0 0, 1 0, 1 1, 0 1, 0 0))', 4326);
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT ST_Contains(@a, @a);
+---------------------+
| ST_Contains(@a, @a) |
+---------------------+
|                   0 |
+---------------------+
1 row in set (0.00 sec)

[11 Sep 2012 14:18] Reinis Rozitis

Present in 5.6.6 m9 too.

[5 Oct 2012 17:04] Paul DuBois

Noted in 5.6.8, 5.7.0 changelogs.

ST_Contains() and ST_Within() incorrectly reported that a polygon did
not contain itself. ST_Equals() incorrectly returned 0 for polygons
that differed only in shifted vertices.