[BUGS] BUG #2209: Low performan on consecutive selects
The following bug has been logged online: Bug reference: 2209 Logged by: Fahri CAKIROGLU Email address: [EMAIL PROTECTED] PostgreSQL version: 8.1 Operating system: Windows nt 2000 Description:Low performan on consecutive selects Details: Consecutive selects from three different tables causes low performance(about 1500 ms). Same select count from two tables gives good performance(about 30 ms). All searched keys are indexed and individual execution of each query is very fast. Slow query : select * from orders where ordernum='1' order by ordernum limit 1; select * from customers where custnum='1' order by custnum limit 1; select * from invoice where invnum='1' order by invnum limit 1; Query with good performance : select * from orders where ordernum='1' order by ordernum limit 1; select * from customers where custnum='1' order by custnum limit 1; select * from orders where ordernum='2' order by ordernum limit 1; select * from customers where custnum='2' order by custnum limit 1; ---(end of broadcast)--- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
Re: [BUGS] BUG #2204: Feature Req: Unique output column names
On 1/24/06, Alvaro Herrera <[EMAIL PROTECTED]> wrote: > Tom Lane wrote: > > > I haven't looked at SQL99 or SQL2003, but most likely they say the same > > thing in two or three times as many words ;-) > > Thanks for the pointer. In SQL 2003, this is 7.12 > : > > 17) Case: > a) If the i-th in the specifies an > that contains a CN, then the >of the i-th column of the result is CN. > b) If the i-th in the does not specify an > and the of that is a >single column reference, then the of the i-th column of >the result is the of the column designated by the >column reference. > c) Otherwise, the of the i-th column of the specification> is implementation dependent. > > So they actually simplified the third rule and we comply with it! > > > It would be nice to have this text in HTML or info format. This PDF > mess is really awkward. Well, then the current behavior is kosher in SQL2003 then, but not neccesarily for SQL92 if someone decided to define some literal column names like "count" or "sum" :) It's not a big deal, just seemed that in certain situations the way other vendors have done it ( "count(x)", "count(y)" ... or .. "1", "2") at least avoid duplication in common cases. -- Brandon ---(end of broadcast)--- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
[BUGS] BUG #2208: Low performance on select
The following bug has been logged online: Bug reference: 2208 Logged by: Fahri CAKIROGLU Email address: [EMAIL PROTECTED] PostgreSQL version: 8.1 Operating system: windows nt 2000 Description:Low performance on select Details: Consecutive selects from three different tables causes low performance(about 1500 ms). Same select count from two tables gives good performance(about 30 ms). All searched keys are indexed and individual execution of each query is very fast. Slow query : select * from orders where ordernum='1' order by ordernum limit 1; select * from customers where custnum='1' order by custnum limit 1; select * from invoice where invnum='1' order by inv limit 1; Query with good performance : select * from orders where ordernum='1' order by ordernum limit 1; select * from customers where custnum='1' order by custnum limit 1; select * from orders where ordernum='2' order by ordernum limit 1; select * from customers where custnum='2' order by custnum limit 1; ---(end of broadcast)--- TIP 2: Don't 'kill -9' the postmaster
[BUGS] BUG #2207: PG Database Server 8.1 Service doesnt start
The following bug has been logged online: Bug reference: 2207 Logged by: Pramod Kudva Email address: [EMAIL PROTECTED] PostgreSQL version: 8.1 Operating system: Windows XP Professional Description:PG Database Server 8.1 Service doesnt start Details: This seems to be a problem since 8.0 and before .. I see a lot of forum activity but never a solution. I installed PG 8.1 with a non-admin user postgres on my windows xp pro laptop. The service doesnt start - and stops saying 'Some services stop automatically when they have nothing to do'. I do have the McAfee Internet Suite 8.0 on my machine but then this error continues even when the mcafee is disabled. Any help is very much appreciated. thanks, pramod ---(end of broadcast)--- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
Re: [BUGS] BUG #2208: Low performance on select
On Wed, Jan 25, 2006 at 12:32:31PM +, Fahri CAKIROGLU wrote: > Consecutive selects from three different tables > causes low performance(about 1500 ms). > Same select count from two tables gives good performance(about 30 ms). This might be due to caching. When you query two tables all of the pages you need might be cached, but when you query a third table some of the pages from the other tables might be evicted from the cache. When you query one of those tables again the pages have to be fetched from disk. How big are the tables in question? > All searched keys are indexed and individual execution > of each query is very fast. Could you post the EXPLAIN ANALYZE output of each query? Have you tuned any of your postgresql.conf settings, in particular shared_buffers? How much memory do you have? -- Michael Fuhr ---(end of broadcast)--- TIP 5: don't forget to increase your free space map settings
