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Re: Question about difference in performance of 2 queries

From: Sean Shanny <shannyconsulting(at)earthlink(dot)net>
To: pgsql-performance(at)postgresql(dot)org
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: Question about difference in performance of 2 queries
Date: 2003-12-29 18:46:09
Message-ID: 3FF07671.7050706@earthlink.net (view raw or flat)
Thread:
Lists: pgsql-performance
Here is the pg_stats data.  The explain analyze queries are still running.

select * from pg_stats where tablename = 'f_pageviews' and attname = 
'date_key';
 schemaname |  tablename  | attname  | null_frac | avg_width | 
n_distinct |             most_common_vals              
|                                         
most_common_freqs                                         
|               histogram_bounds                | correlation
------------+-------------+----------+-----------+-----------+------------+-------------------------------------------+---------------------------------------------------------------------------------------------------+-----------------------------------------------+-------------
 public     | f_pageviews | date_key |         0 |         4 |         
60 | {335,307,309,336,308,321,314,342,322,316} | 
{0.0283333,0.0243333,0.0243333,0.0243333,0.024,0.0233333,0.0226667,0.0226667,0.0223333,0.0216667} 
| {304,311,318,325,329,334,341,346,351,356,363} |    0.345026
(1 row)

select * from pg_stats where tablename = 'f_pageviews' and attname = 
'content_key';
 schemaname |  tablename  |   attname   | null_frac | avg_width | 
n_distinct | most_common_vals |   most_common_freqs   
|                                  
histogram_bounds                                   | correlation
------------+-------------+-------------+-----------+-----------+------------+------------------+-----------------------+-------------------------------------------------------------------------------------+-------------
 public     | f_pageviews | content_key |         0 |         4 |        
983 | {-1,1528483}     | {0.749333,0.00166667} | 
{38966,323835,590676,717061,919148,1091875,1208244,1299702,1375366,1434079,1528910} 
|    0.103399
(1 row)

Thanks.

--sean


Tom Lane wrote:

>Please show EXPLAIN ANALYZE output for your queries, not just EXPLAIN.
>Also it would be useful to see the pg_stats rows for the date_key and
>content_key columns.
>
>			regards, tom lane
>
>  
>


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