[R-sig-Geo] Using duckdb spatial module from R (with sf)?

[Carl Boettiger]

Ah ha.  if we ask duckdb to coerce it's geometry format to hex, it
appears sf can understand it just fine!

replacing the above query with the following we are good to go.



query <- paste(
  'SELECT *, ST_AsHEXWKB(ST_Point(longitude, latitude)) AS geom',
  'FROM "test"'
)
ex <- st_read(con, query=query, geometry_column = "geom", EWKB=FALSE)
ex


I'll experiment further.  I'm terrible at SQL, and to my eyes it looks
needlessly verbose.  I'm keen to understand how I can better leverage
sf's notation to compose the sql queries to duckdb....  but it seems
to work!   I'm also still trying to determine if duckdb is using EWKB
or vanilla WKB....

---
Carl Boettiger
http://carlboettiger.info/

On Tue, Aug 15, 2023 at 4:02 PM Carl Boettiger <cboettig using gmail.com> wrote:
>
> Hi folks,
>
>
> I'm curious if anyone has explored the relatively new spatial
> extension in duckdb (https://duckdb.org/docs/extensions/spatial.html)
> or has any pointers/tutorials regarding its use from R?
>
> Consider the following minimal example that seeks to use the sf
> library to speak to duckdb:
>
>   library(duckdb)
>   library(sf)
>   conn <- DBI::dbConnect(duckdb::duckdb())
>   status <- DBI::dbExecute(conn, "INSTALL 'spatial';")
>   status <- DBI::dbExecute(conn, "LOAD 'spatial';")
>
>   test <- data.frame(site = letters[1:10], latitude = 1:10, longitude = 1:10)
>   DBI::dbWriteTable(conn, "test", test)
>
> # Ok, let's try and make a geometry column
>   query <- paste(
>     'SELECT *, ST_Point(longitude, latitude) AS geom',
>     'FROM "test"'
>   )
>
>   ex <- st_read(con, query=query, geometry_column = "geom")
>   ## error: reading wkb type 0 is not supported
>
>
>   ex <- st_read(con, query=query, geometry_column = "geom", EWKB = FALSE)
>   ## prints: wkbType: 1572864
>   ## Error in CPL_read_wkb(x, EWKB, spatialite) : unsupported wkbType
> dim in switch
>
>  We seem to get closer than I might have hoped (sf doesn't just insist
> that conn isn't postgresgis), but is getting stuck on the encoding of
> the wkb.  Is this something we can work around?  The queries seem to
> run successfully, I just seem to be getting some unsupported ecoding
> of the WKB geometry column....
>
> ---
> Carl Boettiger
> http://carlboettiger.info/