On Tue, Oct 08, 2002 at 12:22:15PM +0530, Savita wrote:
> Hi,
>
> What does the row indicate in the NOTICE: QUERY PLAN:
>
> I am getting diff-2 values which is not same as the actual row present in the table.
Note that EXPLAIN produces an *estimate* of the number of rows. Obviously it
can't know the exact number unless it actually runs the query. EXPLAIN
ANALYZE will give you both the estimate and the actual.
> Seq Scan on os_customer_master (cost=0.00..22.50 rows=10 width=112)
> Index Scan using cust_1 on os_customer_master (cost=0.00..12.22 rows=11 width=112)
>
> I can see that the cost has reduced but the rows has increased. What does
> this means and also what does width means.
It just means that due to some extra info, it estimates closer to 11 than 10
rows. It doesn't say anything about how many rows there really are.
The width is the estimated size of the tuples. If there is only one field
needed, the width will be small. You can see it change if you change the
columns output.
Try EXPLAIN ANALYZE.
--
Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/
> There are 10 kinds of people in the world, those that can do binary
> arithmetic and those that can't.
