PostGIS Snippets: Unterschied zwischen den Versionen
Aus Geoinformation HSR
Stefan (Diskussion | Beiträge) (→hstore) |
Stefan (Diskussion | Beiträge) (→hstore) |
||
Zeile 34: | Zeile 34: | ||
=== Index === | === Index === | ||
+ | Create index for a field of type hstore: | ||
DROP INDEX planet_osm_point_tags; | DROP INDEX planet_osm_point_tags; | ||
CREATE INDEX planet_osm_point_tags | CREATE INDEX planet_osm_point_tags | ||
Zeile 39: | Zeile 40: | ||
USING gin (tags) | USING gin (tags) | ||
+ | Create a index with expression: | ||
DROP INDEX planet_osm_point_tags2; | DROP INDEX planet_osm_point_tags2; | ||
CREATE INDEX planet_osm_point_tags2 | CREATE INDEX planet_osm_point_tags2 | ||
Zeile 54: | Zeile 56: | ||
"italian";197 | "italian";197 | ||
"pizza";123 | "pizza";123 | ||
− | + | ||
− | |||
− | |||
SELECT count(*) AS c, cuisine FROM ( | SELECT count(*) AS c, cuisine FROM ( | ||
SELECT lower(tags->'cuisine') AS cuisine FROM planet_osm_point WHERE tags ? 'cuisine' | SELECT lower(tags->'cuisine') AS cuisine FROM planet_osm_point WHERE tags ? 'cuisine' |
Version vom 16. Februar 2011, 15:24 Uhr
See also:
Inhaltsverzeichnis
Point Constructors
Point constructors for geometry and geography types: Howto construct and print a coordinate in EPSG:4326 and in lon/lat format in either textual or 'symbolic' form?
Works...
/*1 */ SELECT ST_AsEWKT(ST_GeomFromText('POINT(-71.06 42.28)', 4326)) -- ok, preferred if text input /*2 */ SELECT ST_AsEWKT(ST_GeomFromText('SRID=4326;POINT(-71.06 42.28)')) -- ok (if srid 'inline') /*3 */ SELECT ST_AsEWKT(ST_GeomFromEWKT('SRID=4326;POINT(-71.06 42.28)')) -- ok, but why then ST_GeomFromText? /*4 */ SELECT ST_AsEWKT('SRID=4326;POINT(-71.06 42.28)'::geometry) -- ok, but prefer 1/ST_GeomFromText /*5 */ SELECT ST_AsEWKT(ST_SetSRID('POINT(-71.06 42.28)'::geometry, 4326)) -- ok, but prefer 1/ST_GeomFromText /*6 */ SELECT ST_AsEWKT(ST_MakePoint(-71.06, 42.28, 4326)) -- ok for 'symbolic' form. But why no EWKT returning?
Does not work...!
/*1 */ SELECT ST_AsEWKT(ST_GeogFromText('POINT(-71.06 42.28)', 4326)) -- ERROR: unknown ST_GeogFromText(): why? /*2a*/ SELECT ST_AsEWKT(ST_GeogFromText('SRID=4326;POINT(-71.06 42.28)')) -- ERROR: no ST_AsEWKT: why not? /*2b*/ SELECT ST_AsText(ST_GeogFromText('SRID=4326;POINT(-71.06 42.28)')) -- ok (if srid 'inline'); no AsEWKT /*3 */ SELECT ST_AsText(ST_GeogFromEWKT('SRID=4326;POINT(-71.06 42.28)')) -- ERROR: no ST_GeogFromEWKT: why? /*4 */ SELECT ST_AsText('SRID=4326;POINT(-71.06 42.28)'::geography) -- ok (no AsEWKT), but prefer 1/ST_GeomFromText /*5 */ SELECT ST_AsText(ST_SetSRID('POINT(-71.06 42.28)'::geography, 4326)) -- ERROR: ok SetSRID w. geography unnecessary /*6 */ Equivalent to ST_MakePoint for geography types missing: => ST_MakePointG?
Wishlist for future(!) PostGIS developments:
- Create ST_AsEWKT for geography and harmonize ST_AsText (depreciate with EWKT).
- Create ST_GeogFromEWKT for geography and harmonize ST_GeogFromText (depreciate with EWKT).
hstore
Key-Value data type of PostgreSQL.
Index
Create index for a field of type hstore:
DROP INDEX planet_osm_point_tags; CREATE INDEX planet_osm_point_tags ON planet_osm_point USING gin (tags)
Create a index with expression:
DROP INDEX planet_osm_point_tags2; CREATE INDEX planet_osm_point_tags2 ON planet_osm_point USING btree (tags) WHERE tags->'natural'='peak';
Statistics: Counting the different values in hstore
SELECT lower(tags->'cuisine') as tags, count(*) AS count FROM planet_osm_point WHERE tags ? 'cuisine' GROUP BY 1 ORDER BY 2 DESC; "regional";416 "italian";197 "pizza";123 SELECT count(*) AS c, cuisine FROM ( SELECT lower(tags->'cuisine') AS cuisine FROM planet_osm_point WHERE tags ? 'cuisine' UNION ALL SELECT lower(tags->'cuisine') AS cuisine FROM planet_osm_polygon WHERE tags ? 'cuisine' ) AS t GROUP BY cuisine ORDER BY c DESC;