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For GIS/Geometry types, constructor functions are provided. For example, for the LINESTRING data type, the LineString() constructor function can be used to construct a LINESTRING value. Currently, when MariaDB Server tries to cast or convert a value from one geometry type to another (either implicitly or explicitly), different rules appear to be used.
I only tested this on 10.6, but I assume this issue is present on all versions.
Steps to reproduce
Create some objects:
CREATE DATABASE db1;
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USE db1;
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CREATE TABLE linestring_example (
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g LINESTRING
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);
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Try out some different operations:
-- 1.) explicitly call constructor function
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INSERT INTO linestring_example VALUES (LineString(Point(1,1)));
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-- 2.) implicit conversion from POINT to LINESTRING
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INSERT INTO linestring_example VALUES (Point(1,1));
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-- 3.) explicit cast from POINT to LINESTRING
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INSERT INTO linestring_example VALUES (CAST(Point(1,1) AS LINESTRING));
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-- 4.) explicit conversion from POINT to LINESTRING
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INSERT INTO linestring_example VALUES (CONVERT(Point(1,1), LINESTRING));
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Actual results
The only statement that works is the one that explicitly calls the constructor function:
MariaDB [db1]> -- 1.) explicitly call constructor function
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MariaDB [db1]> INSERT INTO linestring_example VALUES (LineString(Point(1,1)));
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Query OK, 1 row affected (0.009 sec)
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MariaDB [db1]> -- 2.) implicit conversion from POINT to LINESTRING
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MariaDB [db1]> INSERT INTO linestring_example VALUES (Point(1,1));
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ERROR 1366 (22007): Incorrect LINESTRING value: 'POINT(1 1)' for column `db1`.`linestring_example`.`g` at row 1
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MariaDB [db1]> -- 3.) explicit cast from POINT to LINESTRING
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MariaDB [db1]> INSERT INTO linestring_example VALUES (CAST(Point(1,1) AS LINESTRING));
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ERROR 4162 (HY000): Operator does not exists: 'CAST(expr AS linestring)'
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MariaDB [db1]> -- 4.) explicit conversion from POINT to LINESTRING
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MariaDB [db1]> INSERT INTO linestring_example VALUES (CONVERT(Point(1,1), LINESTRING));
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ERROR 4162 (HY000): Operator does not exists: 'CAST(expr AS linestring)'
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Expected results
Should all of these cases use similar conversion rules?
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