If you blame your lack of skill on a framework then you probably shouldn't be using that framework. Limitby is supposed to be use to page though results, or to have a window through results, with the idea being you get to scroll your window. I think perhaps we could add a 'top(#)' operator which would be the most obvious choice.
On Tuesday, October 8, 2013 4:45:12 PM UTC-7, Michele Comitini wrote: > > Whenever there is a big performance impact it's better not to make > assumptions on what is the most common use case. > I hate to hear the "web2py is slow" refrain because it's false if you have > a good knowledge of web2py. What concerns me is that doing hidden things > that impact on performance scares the newcomer and the casual tester. > > ------- > Suppose I am new to web2py, but not a newbie to programming and python. I > have a big database and I want to publish things out of it with a nice > framework. I know that accessing the db is critical. I heard web2py is > easy to use. > > I do a simple test. I want to know if there are more than one record of > the kind I am looking for: > > len(db(db.long_table.value=='Am I the only one here?').select( > db.long_table.id, limitby(0,2))) > > I expect it faster than count() on a really big table. Result slow as > hell. Consequence is ... ok I will use a better framework and I will post > somewhere that web2py is nice, but slow, not for serious projects. > ------- > > Even worse in older releases doing a db.long_table(value='Am I the only > one here?') was slow, very slow and those shortcuts in web2py code are used > everywhere. To the casual user it was the clear sign that no one did > serious testing on a large database. > > mic > > > > 2013/10/8 Niphlod <nip...@gmail.com <javascript:>> > >> the smartest thing to do would be to avoid orderby when there are less >> records than paginate. >> However, it's unusual to have a query misbehaving for a couple hundreds >> records, and I really don't see the point on using grid with paginate=10000. >> Given that pagination is 99% of the time required, we need to orderby on >> something.... >> What we should orderby to then? The only assured field that has an >> implicit index is the id (being a PK). Orderby(ing) a PK should definitely >> not require a full scan. >> I don't see any particular case other than exceptional misbehaving tables >> to turn off the ordering. >> >> >> On Tuesday, October 8, 2013 1:53:50 PM UTC+2, Anthony wrote: >>> >>> >>> db.table(id=3) is for returning the sole matching record, so you don't >>>>> have to worry about the database's arbitrary ordering of results. But >>>>> when >>>>> using limitby to return a particular subset of records (e.g., when doing >>>>> pagination), don't you need to specify an orderby to guarantee that the >>>>> results on each query will remain in the same order? >>>>> >>>>> Yes you need to do it, and you need to do it in a proper way. That is >>>> why i think that forcing orderby when limitby is used is not a good idea. >>>> Seems just a hack for the grid, not a generic approach. IMHO it's better >>>> to be explicit. >>>> Consider that on datasets of size comparable to the window imposed by >>>> the limitby, the result is that if one uses limitby then he goes slower >>>> than without it, because of the implicit orderby. Maybe he wonders why >>>> (and >>>> all sorts of bad things about web2py ;- ) >>>> >>> >>> I suppose we could default orderby_on_limitby to False in the general >>> case and leave it to the developer to explicitly orderby when using >>> limitby, but what do you propose for the grid? >>> >>> Anthony >>> >>>> -- >> Resources: >> - http://web2py.com >> - http://web2py.com/book (Documentation) >> - http://github.com/web2py/web2py (Source code) >> - https://code.google.com/p/web2py/issues/list (Report Issues) >> --- >> You received this message because you are subscribed to the Google Groups >> "web2py-users" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to web2py+un...@googlegroups.com <javascript:>. >> For more options, visit https://groups.google.com/groups/opt_out. >> > > -- Resources: - http://web2py.com - http://web2py.com/book (Documentation) - http://github.com/web2py/web2py (Source code) - https://code.google.com/p/web2py/issues/list (Report Issues) --- You received this message because you are subscribed to the Google Groups "web2py-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to web2py+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
