Merge pull request #12 from brownag/gpkg-view

Add spatial view support

NAMESPACE

@@ -28,6 +28,7 @@ export(gpkg_connect)
 export(gpkg_contents)
 export(gpkg_create_contents)
 export(gpkg_create_dummy_features)
+export(gpkg_create_spatial_view)
 export(gpkg_delete_contents)
 export(gpkg_disconnect)
 export(gpkg_execute)

NEWS.md

@@ -1,3 +1,7 @@
+# gpkg 0.0.8
+
+ - Added `gpkg_create_spatial_view()` for creating spatial views, which dynamic layers that are accessible as if they were typical static geometry layers (for #6).
+
 # gpkg 0.0.7
 
  - Added `gpkg_bbox()` as an application of `gpkg_ogr_query()`

R/gpkg-view.R

@@ -0,0 +1,41 @@
+#' Create a Spatial View
+#'
+#' @param g a `geopackage`
+#' @param viewname _character_. Name of view.
+#' @param viewquery _character_. Query for view contents. 
+#' @param geom_column _character_. Column name of view geometry. Default: `"geom"`
+#' @param geometry_type_name _character_. View geometry type. Default: `"GEOMETRY"`
+#' @param spatialite_computed _logical_. Register definition of `geom_column` as
+#'                            the result of a Spatialite spatial function via 
+#'                            `"gdal_spatialite_computed_geom_column"` extension. 
+#'                            Default: `FALSE`
+#' @param data_type _character_. View data type. Default `"features"`
+#' @param srs_id _integer_. Spatial Reference System ID. Default: `4326` (WGS84)
+#' @param z _integer_. Default: `0`
+#' @param m _integer_. Default: `0`
+#'
+#' @return _integer_. Returns `1` if a new record in `gpkg_geometry_columns` is successfully made.
+#' @export
+#'
+gpkg_create_spatial_view <- function(g,
+                                     viewname,
+                                     viewquery, 
+                                     geom_column = "geom",
+                                     geometry_type_name = "GEOMETRY",
+                                     spatialite_computed = FALSE,
+                                     data_type = "features",
+                                     srs_id = 4326,
+                                     z = 0,
+                                     m = 0) {
+gpkg_execute(g, sprintf("CREATE VIEW %s AS %s", viewname, viewquery))
+gpkg_execute(g, sprintf("INSERT INTO gpkg_contents (table_name, identifier, data_type, srs_id) 
+                        VALUES ('%s', '%s', '%s', %s)", 
+                                viewname, viewname, data_type, srs_id))
+gpkg_execute(g, sprintf("INSERT INTO gpkg_geometry_columns (table_name, column_name, geometry_type_name, srs_id, z, m) 
+                        VALUES ('%s', '%s', '%s', %s, %s, %s)",
+                                viewname, geom_column, geometry_type_name, srs_id, z, m))
+if (spatialite_computed)
+  gpkg_execute(g, sprintf("INSERT INTO gpkg_extensions (table_name, column_name, extension_name, definition, scope) 
+                        VALUES ('%s', '%s', 'gdal_spatialite_computed_geom_column', 'https://gdal.org/drivers/vector/gpkg_spatialite_computed_geom_column.html', 'read-write');",
+                                viewname, geom_column))
+}

misc/gpkg-view-voronoi.R

@@ -0,0 +1,34 @@
+library(gpkg)
+library(terra)
+
+gpkg_tmp <- tempfile(fileext = ".gpkg")
+
+if (file.exists(gpkg_tmp))
+  file.remove(gpkg_tmp)
+
+v <- vect(system.file("ex", "lux.shp", package = "terra"))
+
+gpkg_write(list(lux = v), destfile = gpkg_tmp, append = TRUE)
+
+g <- geopackage(gpkg_tmp, connect = TRUE)
+
+gpkg_create_spatial_view(g, "my_vor", "SELECT lux.fid AS OGC_FID, 
+                                              lux.fid AS fid,
+                                              ST_VoronojDiagram(geom) AS geom2 
+                                       FROM lux WHERE ID_2 <= 3", 
+                         geom_column = "geom2", 
+                         geometry_type_name = "MULTIPOLYGON",
+                         spatialite_computed = TRUE) 
+                         # NB: terra::vect() sensitive to geom type
+gpkg_contents(g)
+
+plot(gpkg_vect(g, "my_vor"))        
+gpkg_vect(g, "lux") |> 
+  subset(ID_2 <= 3, NSE = TRUE) |> 
+  as.lines() |> 
+  plot(col = "BLUE", lwd = 2, add = TRUE)
+
+# compare to:
+plot(sf::st_read(g$dsn, layer = "my_vor"))              
+plot(svc(g$dsn, layer = "my_vor")[1])                    
+plot(query(vect(g$dsn, layer = "my_vor", proxy = TRUE)))