The geometry dada is stored in different layer tables according to its type. Data access is through reading and writing the data storing in spatial column of layer table.

• 矢量数据按类型存放在层表(layers tables)的空间数据字段(spatial column)中,每个地理实体对应一条记录。 矢量数据的访问就是对层表中空间数据字段的读写操作。