> Gerry Bendixen wrote: > On: 8 octombrie 2007 16:35 > Subject: RE: Creating new solutions > > Hi all, > The concept presented below involves loading the DB into memory. > My question has to do with the impact on the users computer, if the > memory is reserved for this function. > I'm using Delphi 5. The database could be as much as 200 MB. The > users could be using Win 2000, XP, or Vista. > 1. Does Delphi 5 handle large TStringLists adequately?
Yes and no. It will probably handle a 200 Mb string list, but what will you do with it? I don't think a TStringList is a good data structure for that amount of data. If you're willing to load that much stuff into RAM, you might take the time to create a proper data structure. > 2. Will the DB take away from RAM or will Delphi 5 page it out to > disk? Unless you use very specific API calls (VirtualAlloc & friends) RAM will come out of the Delphi mem manager. Chances are it will initially be RAM and then get swapped to disk. Using a TStringList for 200 Mb of stuff might prevent the RAM from getting swapped to disk because of the sequential way you'll be accessing memory. Even if the string list is sorted, you're still referring directly to the strings in the list and that will most likely keep the strings in RAM. > 3. Are the any quirks in the operating systems that I should know > about? No. 200Mb is not really that much data. > Many thanks for any details on these issue, > Gerry B. > P.S: In my opinion if you're considering keeping 200Mb worth of data into a TStringList you should take the time to implement proper data structures that would better serve your application. Ex: At the simplest you should create an TObject descendent that lists all your fields one-by-one so you're not constantly encoding and decoding strings. You'll then be able to keep all those TObject's in a TObjectList. You might also consider implementing an separate index for your list so you can search for stuff without actually referring to the object in the list itself (this gives the memory manager a chance to move data from RAM to Swap). And of course, another good option would be to use some kind of ready-made in-memory TDataSet descendent. I don't know if Delphi5 has the TClientDataSet but that's a good option. Using an TDataSet descendent gives you a good data structure specifically created to handle large amounts of data in a way that doesn't over-stress the memory manager (because it does not create memory fragmentation - at least it shoudn't). -- Cosmin Prund __________________________________________________ Delphi-Talk mailing list -> Delphi-Talk@elists.org http://www.elists.org/mailman/listinfo/delphi-talk
