BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  OPF Paging List Goto page 1, 2  Next          BorlandTalk.com Forum Index -> Delphi OO design View previous topic :: View next topic   Author Message Marcos Guest Posted: Thu Dec 02, 2004 10:16 pm    Post subject: OPF Paging List I have been using some opf and all of them has two way to return data: 1 - an object list returns 2 - an object list returns based on a criterion In spite of second to be better, when the list of data is big exists always an overhead for bring their and sometimes causing lack of memory (this is a largest problem). I also worked with Datasnap and I noticed the advantages of having an application StateLess. How can I work in the same way in an OPF? I read that Joanna has a Paging List. Will it be that she could explain better how this pagination works? Thanks a lot! Back to top Joanna Carter (TeamB) Guest Posted: Thu Dec 02, 2004 11:14 pm    Post subject: Re: OPF Paging List "Marcos" <mrbar2000 (AT) yahoo (DOT) com.br> a écrit dans le message de news: [email]41af9429 (AT) newsgroups (DOT) borland.com[/email]... Quote: I read that Joanna has a Paging List. Will it be that she could explain better how this pagination works? My paged list eventualy pulls in the whole collection as the user pages through the list GUI. Of course, the problem is if the user does Ctrl-End, in which case you either end up with a delay while the list catches up, or you can reverse the underlying query and start filling from the end of the list. Joanna -- Joanna Carter (TeamB) Consultant Software Engineer TeamBUG support for UK-BUG TeamMM support for ModelMaker Back to top Marcos Guest Posted: Thu Dec 02, 2004 11:53 pm    Post subject: Re: OPF Paging List Quote: My paged list eventualy pulls in the whole collection as the user pages through the list GUI. Of course, the problem is if the user does Ctrl-End, in which case you either end up with a delay while the list catches up, or you can reverse the underlying query and start filling from the end of the list. Ok, but while your list isn't filled your query stay open with data? This not duplicate the data in memory? thanks Back to top Joanna Carter (TeamB) Guest Posted: Fri Dec 03, 2004 12:25 am    Post subject: Re: OPF Paging List "Marcos" <mrbar2000 (AT) yahoo (DOT) com.br> a écrit dans le message de news: [email]41afab11 (AT) newsgroups (DOT) borland.com[/email]... Quote: Ok, but while your list isn't filled your query stay open with data? This not duplicate the data in memory? The only other way would be to run a query that only returns the OIDs into an array or something and then uses the OIDs in theat array to fire off single row queries as the list/grid requires, looking up the OID based on the index of the row in the list/grid as found in the array. Joanna -- Joanna Carter (TeamB) Consultant Software Engineer TeamBUG support for UK-BUG TeamMM support for ModelMaker Back to top Jim Cooper Guest Posted: Fri Dec 03, 2004 1:58 am    Post subject: Re: OPF Paging List Quote: The only other way would be to run a query that only returns the OIDs Or the OIDs and enough data to show in the list (typically ths is small) Cheers, Jim Cooper _______________________________________________ Jim Cooper [email]jim (AT) falafelsoft (DOT) com[/email] Falafel Software http://www.falafelsoft.com _______________________________________________ Back to top Marcos Guest Posted: Fri Dec 03, 2004 5:06 am    Post subject: Re: OPF Paging List Quote: Ok, but while your list isn't filled your query stay open with data? This not duplicate the data in memory? The only other way would be to run a query that only returns the OIDs into an array or something and then uses the OIDs in theat array to fire off single row queries as the list/grid requires, looking up the OID based on the index of the row in the list/grid as found in the array. Very thanks JC. And as to bring the data of form stateless as we do when using Datasnap? I have 300 records into TableA. I have open the list of 300 objects in that table but I want retrieve only 30 records per time. The Server don't hold the start or end record fetched Client. The client should produce this information. I have curios how can us implement this into our opf!!! I am impressed with his/her answer speed Joanna. Very grateful! Back to top Marcos Guest Posted: Fri Dec 03, 2004 6:48 am    Post subject: Re: OPF Paging List Quote: Ok, but while your list isn't filled your query stay open with data? This not duplicate the data in memory? The only other way would be to run a query that only returns the OIDs into an array or something and then uses the OIDs in theat array to fire off single row queries as the list/grid requires, looking up the OID based on the index of the row in the list/grid as found in the array. Very thanks JC and Jim. And as to bring the data of form stateless as we do when using Datasnap? I have 300 records into TableA. I have open the list of 300 objects in that table but I want retrieve only 30 records per time. The Server don't hold the start or end record fetched Client. The client should produce this information. I have curios how can us implement this into our opf!!! I'm impressed with your fast answer. Very grateful! Back to top Roman Kaßebaum Guest Posted: Fri Dec 03, 2004 8:17 am    Post subject: Re: OPF Paging List Joanna Carter (TeamB) schrieb: Quote: The only other way would be to run a query that only returns the OIDs into an array or something and then uses the OIDs in theat array to fire off single row queries as the list/grid requires, looking up the OID based on the index of the row in the list/grid as found in the array. Single row queries are very very slow. -- Roman Back to top Roman Kaßebaum Guest Posted: Fri Dec 03, 2004 8:20 am    Post subject: Re: OPF Paging List Marcos schrieb: Quote: I have 300 records into TableA. I have open the list of 300 objects in that table but I want retrieve only 30 records per time. In some special cases we create more than 30000 objects. There is no problem of memory usage. By the way objects are much more faster than queries. -- Roman Back to top Joanna Carter (TeamB) Guest Posted: Fri Dec 03, 2004 8:30 am    Post subject: Re: OPF Paging List "Roman Kaßebaum" <roman.kassebaumnospam (AT) kdv-dt (DOT) de> a écrit dans le message de news: [email]41b02078 (AT) newsgroups (DOT) borland.com[/email]... Quote: Single row queries are very very slow. That has not been my experience when the query is based on an indexed single integer column. i.e. SELECT * FROM customer WHERE id = 123456 Joanna -- Joanna Carter (TeamB) Consultant Software Engineer TeamBUG support for UK-BUG TeamMM support for ModelMaker Back to top Joanna Carter (TeamB) Guest Posted: Fri Dec 03, 2004 8:37 am    Post subject: Re: OPF Paging List "Marcos" <mrbar2000 (AT) yahoo (DOT) com.br> a écrit dans le message de news: [email]41b00c4d (AT) newsgroups (DOT) borland.com[/email]... Quote: I have 300 records into TableA. I have open the list of 300 objects in that table but I want retrieve only 30 records per time. The Server don't hold the start or end record fetched Client. The client should produce this information. I have curios how can us implement this into our opf!!! The problem with 'dropping' the early records as you pass through the list is that most SQL cursors are unidirectional, therefore you can't get back to earlier records once you have past them. Therefore most dataset components tend to keep all records in memory once they have been read. Overall the efficiencies are greater doing it that way than worrying about memory usage on a Windows OS which allows you 2GB of memory for a process. Anywhere up to a couple of million objects is quite acceptable, although I tend to design my UI to encourage users never to ask for more than a hundred or so objects. I refuse to believe that any user can ever need to browse through that many records without knowing something about the objects they are looking for. Joanna -- Joanna Carter (TeamB) Consultant Software Engineer TeamBUG support for UK-BUG TeamMM support for ModelMaker Back to top Lee_Nover Guest Posted: Fri Dec 03, 2004 8:43 am    Post subject: Re: OPF Paging List Quote: Single row queries are very very slow. That has not been my experience when the query is based on an indexed single integer column. i.e. SELECT * FROM customer WHERE id = 123456 I agree with Roman one select with multiple records eg: .. WHERE ID IN (1, 2, 3, 4, 5, 6) is much faster than a: for I:=1 to 6 do FetchWhere('ID', fwEquals, I); Back to top Lee_Nover Guest Posted: Fri Dec 03, 2004 8:47 am    Post subject: Re: OPF Paging List Quote: By the way objects are much more faster than queries. did some caching to speed things up .. instead of 7secs to fetch the data now only a few ms is needed even if you have a class that takes up 100bytes .. with 1M records that's still _only_ 100MB memory .. which for servers shouldn't be much Back to top Roman Kaßebaum Guest Posted: Fri Dec 03, 2004 9:20 am    Post subject: Re: OPF Paging List Joanna Carter (TeamB) schrieb: Quote: That has not been my experience when the query is based on an indexed single integer column. i.e. SELECT * FROM customer WHERE id = 123456 But that has been my experience. In my example I have a simple loop for every object where I use a property, e. g.: for i := 0 to pList.Count - 1 do pList[iCount].Name := IntToStr(i); I tried two things: First I had a list of ID, so that for every object I'll fire 'select * from Table where ID = ObjectId'. Second I tried 'select * from table'. After that I filled the objects from the query, e.g.: while not pQuery.Eof do begin ObjectById(pIdField.AsInteger).LoadFromDataSet(pQuery); pQuery.Next; end; After that I called the loop. The second example is much more faster than the first one. -- Roman Back to top Jim Cooper Guest Posted: Fri Dec 03, 2004 11:02 am    Post subject: Re: OPF Paging List Quote: Single row queries are very very slow. So you don't call them in big loops. Typically you have a list of some sort showing basic info (all gotten with one query), and detailed info is only requested as required (eg when an editing form is displayed). Sometimes it pays to be a little judicious when scrolling though a long list and only load objects when scrolling stops. Cheers, Jim Cooper _______________________________________________ Jim Cooper [email]jim (AT) falafelsoft (DOT) com[/email] Falafel Software http://www.falafelsoft.com _______________________________________________ Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         BorlandTalk.com Forum Index -> Delphi OO design All times are GMT Goto page 1, 2  Next Page 1 of 2   Jump to: Select a forum C++ Builder Newsgroups----------------C++ BuilderC++ Builder (ActiveX)C++ Builder (Announcements)C++ Builder (Command Line Tools)C++ Builder DatabasesC++ Builder Databases (ADO)C++ Builder Databases (Desktop)C++ Builder Databases (InterBase Express)C++ Builder Databases (Multi-Tier)C++ Builder Databases (SQL Servers)C++ Builder (Graphics)C++ Builder (IDE)C++ Builder (Internet)C++ Builder (Internet Socket)C++ Builder (Internet Web)C++ Builder (Jobs)C++ Builder (Language)C++ Builder (Language C++)C++ Builder (Compatibility with MFC)C++ Builder (Native API)C++ Builder (Non-Technical)C++ Builder (Students)C++ Builder (Third Party Tools)C++ Builder (Upgrade)C++ Builder (VCL)C++ Builder (VCL Components Usage)C++ Builder (VCL Components Development)C++ Builder (VCL Usage)C++ Builder (WinAPI)C++ Builder Installation Delphi Newsgroups----------------Delphi (General)Delphi ActiveX Controls UsageDelphi ActiveX Controls DevelopmentDelphi As400Delphi DatabasesDelphi Databases (ADO)Delphi Databases (dbExpress)Delphi Databases (Desktop)Delphi Databases (InterBase Express)Delphi Databases (Multi-Tier)Delphi Databases (SQL Servers)Delphi DeploymentDelphi GraphicsDelphi IDEDelphi InternationalizationDelphi InternetDelphi Internet Isapi-WebBrokerDelphi Internet WebSnapDelphi Internet WinsockDelphi JobsDelphi Language BASMDelphi Language ObjectPascalDelphi Model Driven Architecture (General)Delphi Model Driven Architecture (Third Party)Delphi MultimediaDelphi Native APIDelphi Non-TechnicalDelphi ObjectPascalDelphi OLE AutomationDelphi OO designDelphi OpenToolsAPIDelphi Reporting-ChartingDelphi RTLDelphi StudentsDelphi TeamSourceDelphi Thirdparty ToolsDelphi Thirdparty Tools (General)Delphi Thirdparty Tools (IntraWeb)Delphi Thirdparty Tools (RaveReports)Delphi UpgradeDelphi VCLDelphi VCL ComponentsDelphi VCL Components UsingDelphi VCL Components WritingDelphi WebServices SOAPDelphi WinAPIDelphi XMLDelphi Installationcomp.lang.pascal.delphi.components.misccomp.lang.pascal.delphi.components.usagecomp.lang.pascal.delphi.components.writingcomp.lang.pascal.delphi.databasescomp.lang.pascal.delphi.misccomp.sources.delphi JBuilder Newsgroups----------------JBuilderJBuilder AnnouncementsJBuilder Applet IssuesJBuilder As400JBuilder CompilerJBuilder CORBA/RMIJBuilder DatabasesJBuilder DB SwingJBuilder DebuggerJBuilder DeploymentJBuilder DocumentationJBuilder EnterpriseJBuilder HandheldJBuilder IDEJBuilder JavaJBuilder JavaAPIJBuilder Java LanguageJBuilder Java SwingJBuilder Java BeansJBuilder Java Beans UsageJBuilder Java Beans DevelopmentJBuilder JBCLJBuilder JDataStoreJBuilder JobsJBuilder LinuxJBuilder MacintoshJBuilder & MobileSetJBuilder MultiLingual AppsJBuilder Non-TechnicalJBuilder OpenToolsJBuilder Servlets (JSP)JBuilder StudentsJBuilder Team DevelopmentJBuilder Thirdparty ToolsJBuilder UpgradeJBuilder Installation InterBase Newsgroups----------------InterBaseInterBase Bug DiscussionInterBase GeneralInterBase IBConsoleInterBase OpenSourceInterBase ReplicationInterBase SQLInterBase ThirdpartyInterBase Installation Miscellaneous Borland Newsgroups----------------AppCenterAppServerEnteraVisiBroker  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.