explain analyze functionality

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От Tourtounis Sotiris
Тема explain analyze functionality
Дата
Msg-id Pine.GSO.4.44.0209162008570.10094-100000@fryni.csd.uch.gr
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Ответы Re: explain analyze functionality  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-general
i have an SQL query of the general type

select att0 from table where 1 <= att0 and att0 < 1000000

to a table of the general format (att0 int4, att1 int4) where there is an
index on att0 and when i run the explain analyze on that question it
returns me the following result:

NOTICE:  QUERY PLAN:

Index Scan using index1 on class y  (cost=0.00..3662.16 rows=1266 width=4)
(actual time=0.44..4323.38 rows=1000000 loops=1)
Total runtime: 4563.40 msec

NOTICE:  QUERY PLAN:

Index Scan using index1 on class y  (cost=0.00..3662.16 rows=1266 width=4)
(actual time=0.44..4323.38 rows=1000000 loops=1)
Total runtime: 4563.40 msec

doews anyone know each of those two index scans, which are stated there
are unique to which of the two conditions refer: to condition 1 <= att0,
to condition att0 < 1000000 or to the union of those two questions? I
would appreciate any opinion, help.




                                                 SWTHRHS TOYRTOYNHS
                                                (tourtoun@csd.uch.gr)




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