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According to the OpenGIS specifications for SQL, geometry sub-types like POINT, LINESTRING, etc. are separate data types. Having separate type handlers Type_handler_point, Type_handler_linestring, etc (instead of a single Type_handler_geometry with a geometry type attribute) will look more natural in the code:
- It will be easier to turn Type_handler_geometry into a plugin, e.g. in the parser. The geometry specific fields in %union in sql_yacc.yy, such as geom_type, will be removed.
- Better error reporting, e.g. precise data type instead of GEOMETRY:
SELECT POINT(0,0)+POINT(0,0);
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ERROR HY000: Illegal parameter data types point and point for operation '+'
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- It will make implementing
MDEV-17832 easier (with a cleaner API).
- It will allow to localize geometry specific things inside Type_handler_geometry, e.g.
- move enum geometry_type from Field to Type_handler_geometry
- remove Item::geometry_type() and Item::set_geometry_type()
To remove geometry specific tests, such as f_is_geom(), from the loop handling keys in mysql_prepare_create_table(), and to simplify adding new data typesr, lets add a few virtual methods:
virtual bool Key_part_spec_init_primary(Key_part_spec *part,
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const Column_definition &def,
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const handler *file) const;
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virtual bool Key_part_spec_init_unique(Key_part_spec *part,
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const Column_definition &def,
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const handler *file,
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bool *has_key_needed) const;
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virtual bool Key_part_spec_init_multiple(Key_part_spec *part,
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const Column_definition &def,
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const handler *file) const;
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virtual bool Key_part_spec_init_foreign(Key_part_spec *part,
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const Column_definition &def,
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const handler *file) const;
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virtual bool Key_part_spec_init_spatial(Key_part_spec *part,
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const Column_definition &def) const;
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With these new methods, data type plugins will be able to decide how to handle various key types.
This also will help to move POINT specific global declaration from sql_table.h inside Type_handler_point:
/* Maximum length of GEOM_POINT Field */
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#define MAX_LEN_GEOM_POINT_FIELD 25
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Let's also add separate classes under Item_func_spatial_collection for all constructor-alike SQL functions, so the hierarchy looks like this:
Item_func_spatial_collection
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Item_func_geometrycollection
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Item_func_linestring
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Item_func_polygon
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Item_func_multilinestring
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Item_func_multipoint
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Item_func_multipolygon
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In the future, it will allow to remove geometry-specific code in the grammar, e.g.:
| GEOMETRYCOLLECTION '(' expr_list ')'
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{
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$$= GEOM_NEW(thd,
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Item_func_spatial_collection(thd, *$3,
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Geometry::wkb_geometrycollection,
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Geometry::wkb_point));
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$$= GEOM_NEW(thd, Item_func_geometrycollection(thd, *$3));
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}
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In a separate MDEV later we'll replace it to something like this:
| user_defined_type_handler_name '(' expr_list ')'
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{
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if (!($$= $1->make_constructor_item($3))
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MYSQL_YYABORT;
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}
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