From: Dan Langille <dan@langille.org>
To: pgsql-sql@postgresql.org
Subject: subselect instead of a view...
Date: Mon, 25 Nov 2002 22:15:41 -0500
Message-ID: <3DE2A10D.5202.D543B95A@localhost> (raw)
Create view WLE_pathnames as
SELECT E.name, EP.pathname
FROM element E,
element_pathnames EP,
watch_list_element WLE
WHERE WLE.watch_list_id = 3724
and WLE.element_id = E.id
and E.id = EP.id;
name | pathname
-------------+-----------------------------
euchre | /ports/games/euchre
reallyslick | /ports/graphics/reallyslick
The above query is pretty well optimized:
Nested Loop (cost=0.00..647.08 rows=62 width=61) (actual
time=0.99..1.19 rows=2 loops=1)
-> Nested Loop (cost=0.00..437.06 rows=62 width=20) (actual
time=0.66..0.78 rows=2 loops=1)
-> Index Scan using watch_list_element_pkey on
watch_list_element wle (cost=0.00..229.64 rows=62 width=4) (actual
time=0.34..0.36 rows=2 loops=1)
-> Index Scan using element_pkey on element e
(cost=0.00..3.34 rows=1 width=16) (actual time=0.16..0.17 rows=1
loops=2)
-> Index Scan using element_pathnames_pkey on element_pathnames ep
(cost=0.00..3.38 rows=1 width=41) (actual time=0.16..0.17 rows=1
loops=2)
Total runtime: 1.44 msec
Now I want to get all the stuff from element_pathnames like
pathname || '/%'. Does that make sense?
Essentially, I want this using the above view:
explain analyze
SELECT E.id, CLE.commit_log_id, E.name, EP.pathname
FROM element E,
element_pathnames EP,
commit_log_elements CLE,
WLE_pathnames WLEP
WHERE E.id = EP.id
AND EP.pathname like WLEP.pathname || '/%'
AND CLE.element_id = E.id
ORDER BY EP.pathname;
I know this can be done better, I just can't figure out how. I keep
thinking of a subselect but I'm totally blocked. It must be bed
time.
Sort (cost=285579.85..285579.85 rows=67012 width=114) (actual
time=9463.95..9464.01 rows=11 loops=1)
-> Hash Join (cost=264060.42..272748.13 rows=67012 width=114)
(actual time=9154.69..9463.55 rows=11 loops=1)
-> Seq Scan on commit_log_elements cle (cost=0.00..3936.75
rows=216575 width=8) (actual time=0.18..1762.38 rows=216575 loops=1)
-> Hash (cost=263370.92..263370.92 rows=36997 width=106)
(actual time=5716.62..5716.62 rows=0 loops=1)
-> Hash Join (cost=258032.99..263370.92 rows=36997
width=106) (actual time=5524.78..5695.47 rows=10 loops=1)
-> Seq Scan on element e (cost=0.00..2286.70
rows=119570 width=16) (actual time=0.15..892.40 rows=119570 loops=1)
-> Hash (cost=257416.50..257416.50 rows=36997
width=90) (actual time=3481.05..3481.05 rows=0 loops=1)
-> Nested Loop (cost=0.00..257416.50
rows=36997 width=90) (actual time=1847.01..3465.54 rows=10 loops=1)
-> Nested Loop (cost=0.00..647.08
rows=62 width=49) (actual time=0.96..1.50 rows=2 loops=1)
-> Nested Loop
(cost=0.00..437.06 rows=62 width=8) (actual time=0.64..0.94 rows=2
loops=1)
-> Index Scan using
watch_list_element_pkey on watch_list_element wle (cost=0.00..229.64
rows=62 width=4) (actual time=0.34..0.37 rows=2 loops=1)
-> Index Scan using
element_pkey on element e (cost=0.00..3.34 rows=1 width=4) (actual
time=0.21..0.22 rows=1 loops=2)
-> Index Scan using
element_pathnames_pkey on element_pathnames ep (cost=0.00..3.38
rows=1 width=41) (actual time=0.21..0.23 rows=1 loops=2)
-> Seq Scan on element_pathnames ep
(cost=0.00..2355.70 rows=119570 width=41) (actual time=0.08..858.74
rows=119570 loops=2)
Total runtime: 9464.51 msec
Clues please?
--
Dan Langille : http://www.langille.org/
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-sql@postgresql.org
Cc: dan@langille.org
Subject: Re: subselect instead of a view...
In-Reply-To: <3DE2A10D.5202.D543B95A@localhost>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox