Re: disable seqscan - Mailing list pgsql-general

Andrew Sullivan <ajs@crankycanuck.ca> wrote:

> On Mon, May 23, 2011 at 05:31:04PM +0530, Nick Raj wrote:
> > Hi,
> > I have build an index. When, i execute the query, it gives the result by
> > sequential scan, not by using my index.
>
> > For that, i have set enable_seqscan=off in postgresql.conf. But it still
> > going through sequential scan.
>
> It sounds like your index can't actually be used to satisfy your
> query.  Without seeing the table definition, index definition, and
> query, however, it's pretty hard to give you a real answer.

... and the output produced by

explain analyse <insert your query>

Explain analyze of my query
explain analyze select * from vehicle_stindex where ndpoint_overlap('(116.4,39.3,2008/02/11 11:11:11),(117.8,39.98,2008/02/13 11:11:11)',stpoint);
                                                                    QUERY PLAN                                                                   
--------------------------------------------------------------------------------------------------------------------------------------------------
 Seq Scan on vehicle_stindex  (cost=10000000000.00..10000050870.86 rows=698823 width=66) (actual time=3285.106..3285.106 rows=0 loops=1)
   Filter: ndpoint_overlap('(116.400000,39.300000,2008-02-11 11:11:11+05:30),(117.800000,39.980000,2008-02-13 11:11:11+05:30)'::ndpoint, stpoint)
 Total runtime: 3285.153 ms
(3 rows)


Table Defination

Table "public.vehicle_stindex"
 Column  |  Type   | Modifiers
---------+---------+-----------
 regno   | text    |
 stpoint | ndpoint |
Indexes:
    "stindex" gist (stpoint)

It has 2099192 tuples.


Index defination
create index stindex on vehicle_stindex using gist(stpoint).


I have defined a datatype called ndpoint. It works same as contrib/cube code (cube datatype).
Query is working fine. I mean no error from query or my datatype. All are giving right result.

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