The first thing to point out is that the estimated cost is measured in terms of page reads while the actual time is measured in milliseconds. So even if the cost estimate is accurate it is unlikely that those numbers will be the same.
-N -- Nathan C. Burnett Research Assistant, Wisconsin Network Disks Department of Computer Sciences University of Wisconsin - Madison [EMAIL PROTECTED] On Wed, 17 Jul 2002, Luis Alberto Amigo Navarro wrote: > I have a query and estimations and results donīt look similar, here is explain >analyze: > > NOTICE: QUERY PLAN: > > Sort (cost=12443.90..12443.90 rows=1 width=93) (actual time=505331.94..505332.67 >rows=175 loops=1) > -> Aggregate (cost=12443.88..12443.89 rows=1 width=93) (actual >time=472520.29..505326.48 rows=175 loops=1) > -> Group (cost=12443.88..12443.89 rows=1 width=93) (actual >time=472307.31..485173.92 rows=325302 loops=1) > -> Sort (cost=12443.88..12443.88 rows=1 width=93) (actual >time=472307.24..473769.79 rows=325302 loops=1) > -> Nested Loop (cost=12439.25..12443.87 rows=1 width=93) >(actual time=103787.68..441614.43 rows=325302 loops=1) > -> Hash Join (cost=12439.25..12440.64 rows=1 width=85) >(actual time=103733.76..120916.86 rows=325302 loops=1) > -> Seq Scan on nation (cost=0.00..1.25 rows=25 >width=15) (actual time=7.81..8.72 rows=25 loops=1) > -> Hash (cost=12439.25..12439.25 rows=1 width=70) >(actual time=103722.25..103722.25 rows=0 loops=1) > -> Nested Loop (cost=0.00..12439.25 rows=1 >width=70) (actual time=95.43..100162.91 rows=325302 loops=1) > -> Nested Loop (cost=0.00..12436.23 >rows=1 width=62) (actual time=84.91..47502.93 rows=325302 loops=1) > -> Nested Loop >(cost=0.00..12412.93 rows=4 width=24) (actual time=66.86..8806.01 rows=43424 loops=1) > -> Seq Scan on part >(cost=0.00..12399.00 rows=1 width=4) (actual time=24.88..4076.81 rows=10856 loops=1) > -> Index Scan using >partsupp_pkey on partsupp (cost=0.00..13.89 rows=4 width=20) (actual time=0.20..0.34 >rows=4 loops=10856) > -> Index Scan using >l_partsupp_index on lineitem (cost=0.00..6.02 rows=1 width=38) (actual >time=0.20..0.61 rows=7 loops=43424) > -> Index Scan using supplier_pkey on >supplier (cost=0.00..3.01 rows=1 width=8) (actual time=0.08..0.10 rows=1 >loops=325302) > -> Index Scan using orders_pkey on orders >(cost=0.00..3.22 rows=1 width=8) (actual time=0.85..0.87 rows=1 loops=325302) > Total runtime: 505563.85 msec > > estimated 12000msec > > here is the query: > SELECT > nation, > o_year, > CAST((sum(amount))AS NUMERIC(10,2))AS sum_profit > FROM( > SELECT > nation.name AS nation, > EXTRACT(year FROM orders.orderdate) AS o_year, > lineitem.extendedprice*(1-lineitem.discount)-partsupp.supplycost*lineitem.quantity >AS amount > FROM > part, > supplier, > lineitem, > partsupp, > orders, > nation > WHERE > supplier.suppkey=lineitem.suppkey > AND partsupp.suppkey=lineitem.suppkey > AND partsupp.partkey=lineitem.partkey > AND part.partkey=lineitem.partkey > AND orders.orderkey=lineitem.orderkey > AND supplier.nationkey=nation.nationkey > AND part.name LIKE '%green%' > ) AS profit > GROUP BY > nation, > o_year > ORDER BY > nation, > o_year DESC; > > lineitem is about 6M rows > partsupp 800K rows > part 200K rows > > any advice? > Thanks and regards > > > ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster
