Greetings, I've been toying aroudn with postgres 7.1beta5's ability to control the planner via explicitely JOINing
tables.I then (just for giggles) compare the difference in the EXPLAIN results.
I'm no super-mondo-DBA or anything, but in my two attempts so far, the numbers I get out of EXPLAIN have been about
1/2as small.
Below are two EXPLAIN results, am I correct in reading that one is indeed "twice as fast" as the other? I say twice as
fastbecause the top-most cost in the first query is 58.62, but in the second one it's only 32.09. Am I reading this
correctly?
-- First EXPLAIN --
Sort (cost=58.62..58.62 rows=14 width=60) -> Nested Loop (cost=0.00..58.35 rows=14) -> Nested Loop
(cost=0.00..29.99rows=14) -> Seq Scan on playlist p (cost=0.00..1.61 rows=14) -> Index Scan using songs_pkey
onsongs s (cost=0.00..2.01 rows=1) -> Index Scan using artists_pkey on artists a (cost=0.00..2.01 rows=1)
-- Second EXPLAIN --
Sort (cost=32.09..32.09 rows=1) -> Nested Loop (cost=0.00..32.08 rows=1) -> Nested Loop (cost=0.00..30.06
rows=1) -> Seq Scan on playlist p (cost=0.00..1.61 rows=14) -> Index Scan using songs_pkey on songs s
(cost=0.00..2.02rows=1) -> Index Scan using artists_pkey on artists a (cost=0.00..2.01 rows=1)
-- Dave
