Our production database is running under 7.2.4; our test database running almost the same data is at 7.3.3. One table has about 400,000 rows in each schema. A query against an indexed column uses an index scan under 7.2.4, but a sequential scan under 7.3.3. A count of the table in question shows that they have comparable numbers of matching rows.
On 7.2.4: select count(*) from articles; count -------- 420213 select count(*) from articles where path_base like 'http://news.findlaw.com/hdocs%'; count ------- 38 (and it returns this nearly instantaneously) explain select count(*) from articles where path_base like 'http://news.findlaw.com/hdocs%' Aggregate (cost=6.02..6.02 rows=1 width=0) -> Index Scan using ix_articles_3 on articles (cost=0.00..6.01 rows=1 width=0) On 7.3.3: select count(*) from articles; count -------- 406319 select count(*) from articles where path_base like 'http://news.findlaw.com/hdocs%' count ------- 23 (and it takes many seconds to return) explain select count(*) from articles where path_base like 'http://news.findlaw.com/hdocs%' Aggregate (cost=205946.65..205946.65 rows=1 width=0) -> Seq Scan on articles (cost=0.00..205946.65 rows=1 width=0) Filter: (path_base ~~ 'http://news.findlaw.com/hdocs%'::text) I can't find any differences between the indexes (ix_articles_3 exists in both schemas); the column statistics are set up the same (the default); and the optimizer settings (costs in postgresql.conf) are the same. -- Jeff Boes vox 269.226.9550 ext 24 Database Engineer fax 269.349.9076 Nexcerpt, Inc. http://www.nexcerpt.com ...Nexcerpt... Extend your Expertise ---------------------------(end of broadcast)--------------------------- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])
