PostgreSQL: postGIS functions

Change to Posgres (database user)

pi@raspberrypi /home/uki $ su postgres

Password: 

postgres@raspberrypi:/home/uki$

Select correct database

postgres@raspberrypi:/home/uki$  psql -d polygons

psql (9.1.12)

Type "help" for help.

polygons=#

To exit PostgreSQL shell

polygons=# \q

Select number of Points per Polygon in database

polygons=# select ST_NPoints(polygon) from polygon;

107ms on Respberry Pi

 st_npoints
------------
        132
        132
         12
          6
         26
         57
         15
          6
         18
         26
         19
          8
          6
          6
         14
         13
         10
         58
         10
          8
        171
        171

Select polygons for the GEO point

polygons=# select ST_NPoints(polygon) points from polygon where ST_Contains(polygon, ST_GeomFromText('POINT(-89.2535979 37.9210949)'));

Alternatively you can run query from Linux user prompt

postgres@raspberrypi:/home/pi$ psql -d polygons -c 'select ST_NPoints(polygon) from polygon;' 

If you testing timing of your query then you have to turn it on

polygons=# \timing

Timing is on.

polygons=# select ST_NPoints(polygon) from polygon;

Time: 17.256 ms