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

Any improvement is welcomed. The overall performance of the application is
not very good. It takes about 200 seconds to compute a path for not so far
star and end points. I want to improve this query as much as I can.
How exactly should I post the explain without the index? Do I have to drop
all created indexes for the tags column? It takes some time to create them
back.

On Mon, Jul 8, 2013 at 11:53 AM, Richard Huxton <dev(at)archonet(dot)com> wrote:

> On 08/07/13 09:31, Radu-Stefan Zugravu wrote:
>
>> Hi,
>> Thank you for your answer.
>> My EXPLAIN ANALYZE output can be found here:
>> http://explain.depesz.com/s/**Wbo <http://explain.depesz.com/s/Wbo>.
>>
>
> Thanks
>
> Also, there is a discution on this subject on dba.stackexchange.com
>> <http://dba.stackexchange.com>**:
>> http://dba.stackexchange.com/**questions/45820/how-to-**
>> properly-index-hstore-tags-**column-to-faster-search-for-**keys<http://dba.stackexchange.com/questions/45820/how-to-properly-index-hstore-tags-column-to-faster-search-for-keys>
>>
>
> Thanks - also useful to know.
>
> I can't see anything wrong with your query. Reading it from the bottom
> upwards:
> 1. Index used for "historic" search - builds a bitmap of blocks
> 2. Index used for geometry search - builds a bitmap of blocks
> 3. See where the bitmaps overlap (BitmapAnd)
> 4. Grab those disk blocks and find the rows (Bitmap Heap Scan)
>
> The whole thing takes under 20ms - what sort of time were you hoping for?
>
> The bulk of it (15ms) is taken up locating the "historic" rows. There are
> 36351 of those, but presumably most of them are far away on the map.
>
> Could you post the explain without the index? I'm curious as to how slow
> it is just testing the tags after doing the geometry search.
>
>
> --
> Richard Huxton
> Archonet Ltd
>

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Radu-Stefan Zugravu
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