And, BTW, "data file + supplementary file for faster access" isn't anywhere near how SQLite operates. SQL is like a Swiss Army Knife -- great if you frequently need a corkscrew, but a lot of dead weight if you don't.
On Oct 4, 1:25 pm, Tom Gibara <[email protected]> wrote: > This combination of a data file + supplementary file for faster access, is > indeed very well established. Developers have spent considerable time > providing robust and efficient implementations, where they are often > referred to as tables and indexes, and exposed via a software component > that's often called a database. > > Tom. > > On 4 October 2010 18:45, DanH <[email protected]> wrote: > > > Well, when I look at the web references for "dope vector", they're > > mostly referring to a different (and more obscure) concept than the > > one I'm talking about: > > > The concept is blazingly simple -- something you'd invent if you > > didn't already know of it. > > > Consider that you have a set of variable-length elements (maybe > > strings) that you want to access by numeric index, you could allocate > > an NxM byte array (where M is the size of the longest element) but > > that would be inefficient (in space) if many of the elements were much > > shorter than M. > > > So instead you pack the elements together, head to tail, in a single > > byte array. Then you create another array, Nx2 integers. If you > > index this second array by the "index" of one of your variable-length > > elements, the first word in the row is the offset to the start of that > > element (within the first array), and the second word is the length of > > the element. > > > But then you notice that, for all elements except the last, for a > > given element index X, the X+1 entry in the dope vector contains the > > offset of the first byte after the Xth element. So instead of having > > two columns in the dope vector you can (if you wish) just use one, and > > add at the end an N+1th entry that addresses the first byte after the > > end of the last element. > > > In this case, you replace the arrays with randomly-accessed files, but > > that's a trivial transformation (aside, as I said, from the ugliness > > of the Java file access classes). > > > On Oct 4, 11:51 am, Mark Murphy <[email protected]> wrote: > > > On Mon, Oct 4, 2010 at 12:38 PM, DanH <[email protected]> wrote: > > > > Background in algorithms??? It's a Programming 101 problem -- anyone > > > > with a modicum of programming skill should be able to do it. > > > > You make a few assumptions, in terms of background and experiences, > > > that may or may not be accurate. > > > > > It's no > > > > harder than writing the program to read lines from a file and write > > > > them to a database -- the only real difficulty is navigating through > > > > the maze of Java classes you need to do file access. > > > > The lines of code count is probably somewhat longer. More importantly, > > > though, the database solution is well-trod ground, with quite a few > > > samples. "Dope vector" has remarkably few hits on search engines, let > > > alone any code that can be readily applied in this case. Now, > > > admittedly, not every occurrence of this pattern may use that term -- > > > when I used a variant on this approach on the Apple IIe in the late > > > 1980's, I had not heard of the term. > > > > Perhaps you would like to contribute, by either augmenting the dope > > > vector Wikipedia page, or by creating a couple of Java classes for > > > creating and reading dope vector files, to help make it easier for > > > people to take advantage of your expertise in this area. > > > > -- > > > Mark Murphy (a Commons Guy)http://commonsware.com| > >http://github.com/commonsguyhttp://commonsware.com/blog|http://twitter.com/commonsguy > > > > Android Training...At Your Office:http://commonsware.com/training > > > -- > > You received this message because you are subscribed to the Google > > Groups "Android Developers" group. > > To post to this group, send email to [email protected] > > To unsubscribe from this group, send email to > > [email protected]<android-developers%[email protected]> > > For more options, visit this group at > >http://groups.google.com/group/android-developers?hl=en -- You received this message because you are subscribed to the Google Groups "Android Developers" 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/android-developers?hl=en
