Hi NIck Thank you so much! So if I have merge join queries and if I can spare resources on a custom index, there may be room for improvement on read performance? I guess I could find this out with a larger data set on the production server and query before / after building a custom index.
Herbert On Apr 28, 5:38 pm, "Nick Johnson (Google)" <[email protected]> wrote: > Hi Herbert, > > Merge join queries - queries with multiple equality filters but no > inequalities or sort orders - are a special case. They can be satisfied > using the built in indexes and a merge join strategy, but they can also use > a custom index. The production environment will use the index if it's > present, and otherwise will do a merge join. > > Generally, a merge join works well, but there are situations in which it > doesn't - in which case you may need to add an explicit index. > > -Nick Johnson > > > > On Wed, Apr 28, 2010 at 4:42 AM, Herbert <[email protected]> wrote: > > Hi Nick > > > Thank you. One thing I'm still a bit confused about index. I had the > > impression that if I've executed all kinds of queries before I deploy, > > all required indexes would be included, am I correct? > > > Does building a custom index improve performance on complex queries > > even though it is not required? Or I could just stick to the rules > > from the doc, and make sure I cover all queries before I deploy? > > > Thanks! > > > On Apr 27, 6:59 pm, "Nick Johnson (Google)" <[email protected]> > > wrote: > > > Hi Herbert, > > > > A query like this will use the merge join strategy by default. If it's > > too > > > slow for the merge join strategy, you could have to build a custom index > > for > > > it, which would indeed be 'exploding' - each User entity would have > > > len(friends)*len(likes) index entries. > > > > -Nick > > > > On Mon, Apr 26, 2010 at 3:20 PM, Herbert <[email protected]> wrote: > > > > Sorry, suddenly got a thought on it. > > > > > Can I do two equality check on both User.friends and User.likes ? > > > > would that be cause an "exploding index?" > > > > > I.E. User.all().filter("friends =", me).filter("likes =", A).fetch(3) > > > > > thanks! > > > > Herbert > > > > > -- > > > > You received this message because you are subscribed to the Google > > Groups > > > > "Google App Engine" group. > > > > To post to this group, send email to [email protected] > > . > > > > To unsubscribe from this group, send email to > > > > [email protected]<google-appengine%[email protected]> > > <google-appengine%[email protected]<google-appengine%[email protected]> > > > > > . > > > > For more options, visit this group at > > > >http://groups.google.com/group/google-appengine?hl=en. > > > > -- > > > Nick Johnson, Developer Programs Engineer, App Engine Google Ireland Ltd. > > :: > > > Registered in Dublin, Ireland, Registration Number: 368047 > > > Google Ireland Ltd. :: Registered in Dublin, Ireland, Registration > > Number: > > > 368047 > > > > -- > > > You received this message because you are subscribed to the Google Groups > > "Google App Engine" group. > > > To post to this group, send email to [email protected]. > > > To unsubscribe from this group, send email to > > [email protected]<google-appengine%[email protected]> > > . > > > For more options, visit this group athttp:// > > groups.google.com/group/google-appengine?hl=en. > > > -- > > You received this message because you are subscribed to the Google Groups > > "Google App Engine" group. > > To post to this group, send email to [email protected]. > > To unsubscribe from this group, send email to > > [email protected]<google-appengine%[email protected]> > > . > > For more options, visit this group at > >http://groups.google.com/group/google-appengine?hl=en. > > -- > Nick Johnson, Developer Programs Engineer, App Engine Google Ireland Ltd. :: > Registered in Dublin, Ireland, Registration Number: 368047 > Google Ireland Ltd. :: Registered in Dublin, Ireland, Registration Number: > 368047 > > -- > You received this message because you are subscribed to the Google Groups > "Google App Engine" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group > athttp://groups.google.com/group/google-appengine?hl=en. -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en.
