Danny Tramnitzke wrote: > > Hi all back > > Today I tried out the 25-BuildVersion of sapdb, hopening for > a performance > increase. But there is still a Query, which takes more than > 10 minutes ( > after that time I killed the process). > > So I seperated the subqueries from that Query, and found out, > that they are > the main reason for the performance lag. They take about 20 > seconds while > first executing. Strange: they only take 2-3 seconds, while > executing them > a second or a thirt time.. (maybe, there is saved some DATA > in a Cache ? ) > But I guess, the main problem are the ca. 20 seconds, they > need the first > time. So the hole query has 3 Subqueries. The main Query without the > subqueries takes only some seconds, and so should it be. > > The Subqueries have the following form : > > ( > Select 1 from SYSDBA.DUAL where exists ( > select a.column from view a, view b, view c where condition1 > and condition2 > and condition3 and condition4 and condition5 and not exist ( > select d.column from view d, view e, view f where condition1 > and condition2 > and condition3 and condition4 and condition5) > ) > > > You see, there are also Subqueries in Subqueries. > The EXPLAIN Statement tells me, that there is only one > Tablescan on the > DUAL Table, else only used Indices. > The Statistics is also up to date...
I do not think that you told us all what is needed. Exists-Subqueries are ... well, strange, not to say stupid if they do not include correlations. Therefore I assume you do not have a simple subquery (as it seems if your shortened 'example' is seen) but a correlated subquery. But then I do not know how you could seperate those subqueries from the whole subquery without changing the conditions. To shorten things: please provide the real statement and the explain for this. Thank you Elke SAP Labs Berlin _______________________________________________ sapdb.general mailing list [EMAIL PROTECTED] http://listserv.sap.com/mailman/listinfo/sapdb.general
