Re: How to properly index hstore tags column to faster search for keys

On 07/07/13 08:28, Radu-Stefan Zugravu wrote:
> Each node has a geometry column called geom and a hstore column
> called tags. I need to extract nodes along a line that have certain
> keys in the tags column. To do that I use the following query:

> SELECT id, tags
> FROM nodes
> WHERE ST_DWithin(nodes.geom, ST_MakeLine('{$geom1}', '{$geom2}'), 0.001)
> AND tags ? '{$type}';

> CREATE  INDEX  nodes_tags_idx ON nodes USING GIN(tags);
>
> After creating the index I searched again for nodes using the same first
> query but there is no change in performance.
>
> How can I properly use GIN and GIST to index tags column so I can faster
> search for nodes that have a certain key in tags column?

Your index definition looks OK. Try showing the output of EXPLAIN 
ANALYSE for your query - that way we'll see if the index is being used. 
You can always paste explain output to: http://explain.depesz.com/ if 
it's too long for the email.

-- 
   Richard Huxton
   Archonet Ltd