1、几何simple和valid有区别，simple主要指线的状态，valid主要指polygon的状态
2、pg默认不做geometry的有效性检查
By default, PostGIS does not apply this validity check on geometry input, because testing for validity needs lots of CPU time for complex geometries, especially polygons. If you do not trust your data sources, you can manually enforce such a check to your tables by adding a check constraint:
ALTER TABLE mytable ADD CONSTRAINT geometry_valid_check CHECK (ST_IsValid(the_geom));
http://www.postgis.net/docs/using_postgis_dbmanagement.html#OGC_Validity
