id,page,ref,title,content,breadcrumbs,references
spatialite:making-use-of-a-spatial-index,spatialite,making-use-of-a-spatial-index,Making use of a spatial index,"SpatiaLite spatial indexes are R*Trees. They allow you to run efficient bounding box queries using a sub-select, with a similar pattern to that used for  Searches using custom SQL . 
             In the above example, the resulting index will be called  idx_museums_point_geom . This takes the form of a SQLite virtual table. You can inspect its contents using the following query: 
             select * from idx_museums_point_geom limit 10; 
             Here's a live example:  timezones-api.datasette.io/timezones/idx_timezones_Geometry 
             
                 
                     
                     
                     
                     
                     
                     
                         
                             
                                 pkid 
                             
                             
                                 xmin 
                             
                             
                                 xmax 
                             
                             
                                 ymin 
                             
                             
                                 ymax 
                             
                         
                     
                     
                         
                             
                                 1 
                             
                             
                                 -8.601725578308105 
                             
                             
                                 -2.4930307865142822 
                             
                             
                                 4.162120819091797 
                             
                             
                                 10.74019718170166 
                             
                         
                         
                             
                                 2 
                             
                             
                                 -3.2607860565185547 
                             
                             
                                 1.27329421043396 
                             
                             
                                 4.539252281188965 
                             
                             
                                 11.174856185913086 
                             
                         
                         
                             
                                 3 
                             
                             
                                 32.997581481933594 
                             
                             
                                 47.98238754272461 
                             
                             
                                 3.3974475860595703 
                             
                             
                                 14.894054412841797 
                             
                         
                         
                             
                                 4 
                             
                             
                                 -8.66890811920166 
                             
                             
                                 11.997337341308594 
                             
                             
                                 18.9681453704834 
                             
                             
                                 37.296207427978516 
                             
                         
                         
                             
                                 5 
                             
                             
                                 36.43336486816406 
                             
                             
                                 43.300174713134766 
                             
                             
                                 12.354820251464844 
                             
                             
                                 18.070993423461914 
                             
                         
                     
                 
             
             You can now construct efficient bounding box queries that will make use of the index like this: 
             select * from museums where museums.rowid in (
    SELECT pkid FROM idx_museums_point_geom
    -- left-hand-edge of point > left-hand-edge of bbox (minx)
    where xmin > :bbox_minx
    -- right-hand-edge of point < right-hand-edge of bbox (maxx)
    and xmax < :bbox_maxx
    -- bottom-edge of point > bottom-edge of bbox (miny)
    and ymin > :bbox_miny
    -- top-edge of point < top-edge of bbox (maxy)
    and ymax < :bbox_maxy
); 
             Spatial indexes can be created against polygon columns as well as point columns, in which case they will represent the minimum bounding rectangle of that polygon. This is useful for accelerating  within  queries, as seen in the Timezones API example.","[""SpatiaLite""]","[{""href"": ""https://timezones-api.datasette.io/timezones/idx_timezones_Geometry"", ""label"": ""timezones-api.datasette.io/timezones/idx_timezones_Geometry""}]"