Re: Creating index does not make any change in query plan.

Hi Martijn,

After doing Vacuum analyzing only I started doing the test. The
table also had nearly 1 lakh record. Then what could be the possible
reason.

On Mon, 17 Feb 2003, Martijn van Oosterhout wrote:

> On Mon, Feb 17, 2003 at 01:06:26PM +0530, Deepa wrote:
> > Hi,
> > When I do explain on 'activealarms' table while selecting
> > a row with primary key (AFAIK while creating primary key, an index will be
> > created on that column), the following result occurs.
> >
> > EXPLAIN SELECT * from activealarms where recordid = 2;
> > NOTICE: QUERY PLAN:
> >
> > Seq Scan on activealarms (cost=0.00..7122.86 rows=1 width=189)
> >
> > EXPLAIN
> >
> > Here 'recordid' is the primary key whose datatype is bigint.
>
> Out of curiosity, what happens with:
>
> EXPLAIN SELECT * from activealarms where recordid = '2';
>
> > I cannot see difference in Query plan for a select query using primary key
> > and non primary key value. Then what could be the use of a field to be
> > used as a primary key.
>
> The planner doesn't care about primary and non-primary keys, it cares about
> indexes (unique and non-unique).
>
> Make sure you've run analyze recently and your tables are big enough to make
> an index scan worthwhile.
>
> Hope this helps,
>

--

Bye,
Deepa. K

--
Engineer,
Network Management System,
Midas Communication Technologies private Ltd,
Chennai.