removing specific Key and value from Hstore in postgres

Question

how to select just red area i have a data which is in Hstore form so i want to select a specific key and value from data and then delete them, as i use this query it is find all rows which this key and value exist on it but i want those rows which is only involve this key and value not all

select * from topdog where tags @> 'created_by=>JOSM'

thanks

• Erwin Brandstetter: I have read your question several times but still don't understand what you want to achieve exactly. Can you clarify? And provide your Postgres version and table definition.
• jack: i am using Postgres 9.3 the question is "i want to delete those rows which has just tags("created_by"=>''JOSM'). when i use this query select * from topdog where tags @> 'created_by=>JOSM' the result is : 16382115;""name"=>"Vazební věznice Brno", "amenity"=>"prison", "created_by"=>"JOSM""; 18008930;""created_by"=>"JOSM""; 21288991;""created_by"=>"JOSM""; 8166183;""source"=>"uhul:ortofoto", "highway"=>"footway", "created_by"=>"JOSM""; but i want to selected and then delete only rows with tags ""created_by"=>"JOSM"" not all rows
• til_b: I hope you don't want to do a OSM mechanical edit to remove those created_by tags; this is discouraged. See wiki.openstreetmap.org/wiki/Key:created_by , specially You should not remove the created_by tag on objects you are not otherwise modifying. If we wanted to remove them in bulk we'd do it some other way.

Answer 1

Seems that you should use the = (equality) operator instead of @>(containment).

It will filter only the exact rows and you could use them in a delta statment.

• jack: i have try this and works : select * from topdog where tags = '"created_by"=>"JOSM"' thanks

Answer 2

use

select * from <table> where tags->'created_by' = 'JOSM' and len(akeys("tags"))=1

That way you select those that have the created_by tag and only one hstore key.

I don't know if len() is the correct function to use for "array element count" (maybe it's array_length()).

See the hstore doc at https://www.postgresql.org/docs/9.1/static/hstore.html .

(Disclaimer: I dont have a hstore enabled db to test with)