Oh, I see how you were thinking. Actually, the code was secondary - it was only meant to illustrate the structure of the data.
In "real life", I will not be using that code to create the segmented strings. It'll be more involved. Thanks, -- Raul On Wed, Apr 9, 2014 at 9:43 PM, Linda Alvord <[email protected]> wrote: > Your example FirstName=:;LF&,each }.0{"1 table is a string creation. > > Mine ]FN2=: >"0 }.0{"1 table is a table. > > If you create tables of character dat and tables of the numeric data > separately, you could transform the numeric data and then join columns to > columns or rows to rows. > > More dimensions could be created as well and then joined in ways to summarize > the useful data and finally rejoin the results. > > My suggestion is really only related to giving thought to how best to extract > and use the string table you have created. > > Linda > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Raul Miller > Sent: Wednesday, April 09, 2014 10:06 AM > To: Programming forum > Subject: Re: [Jprogramming] "Segmented Strings" > > How? > > Thanks, > > -- > Raul > > > > On Wed, Apr 9, 2014 at 3:44 AM, Linda Alvord <[email protected]>wrote: > >> I would not get rid of your table made of strings. I would access it in >> the form of J tables because that is what J does nicely. >> >> Linda >> >> -----Original Message----- >> From: [email protected] [mailto: >> [email protected]] On Behalf Of Raul Miller >> Sent: Wednesday, April 09, 2014 2:48 AM >> To: Programming forum >> Subject: Re: [Jprogramming] "Segmented Strings" >> >> The plan is that segmented strings are the data in the database. >> >> There's just too much information to hold it all in memory on a single >> machine. >> >> Thanks, >> >> -- >> Raul >> >> >> On Wed, Apr 9, 2014 at 2:23 AM, Linda Alvord <[email protected] >> >wrote: >> >> > I know almost nothing about large databases, but what is the advantage of >> > staying with sstrings after the data base is built? >> > >> > Once you have your table, or maybe two or more tables of character and >> > numeric data, you might "stay in J and make "subtables" which can be >> > catenated together and destroyed as needed. You could also do selections >> > of subsets more easily. >> > >> > ]FirstName=:;LF&,each }.0{"1 table >> > >> > Adam >> > Travis >> > Donald >> > Gary >> > James >> > Sam >> > Travis >> > Adam >> > Walter >> > >> > ]FN2=: >"0 }.0{"1 table >> > Adam >> > Travis >> > Donald >> > Gary >> > James >> > Sam >> > Travis >> > Adam >> > Walter >> > >> > FN2-:FirstName >> > 0 >> > $FirstName >> > 53 >> > $FN2 >> > 9 6 >> > >> > Linda >> > >> > >> > -----Original Message----- >> > From: [email protected] [mailto: >> > [email protected]] On Behalf Of Raul Miller >> > Sent: Tuesday, April 08, 2014 8:22 PM >> > To: Programming forum >> > Subject: Re: [Jprogramming] "Segmented Strings" >> > >> > I might indeed do that, but in some cases the time to read the file >> itself >> > will be mostly network transfer time. And, once it's in memory, how it >> got >> > there isn't really an issue. >> > >> > Still, it's worth benchmarking. >> > >> > Thanks, >> > >> > -- >> > Raul >> > >> > >> > On Tue, Apr 8, 2014 at 8:18 PM, Vijay Lulla <[email protected]> >> wrote: >> > >> > > I second memory mapped files and mapped file database. >> > > >> > > >> > > On Tue, Apr 8, 2014 at 4:51 PM, Raul Miller <[email protected]> >> > wrote: >> > > >> > > > It's available for free now, with some limitations: >> > > > >> > > > http://kx.com/software-download.php >> > > > >> > > > It'll take me a few years, though, to develop a fluency in K (Q >> > actually, >> > > > or kdb+ ...) which approaches my fluency in other languages. Anyways, >> > > it's >> > > > not at all clear that K (or Q or KDB+) would be any better for this >> > > > application than J. The grass is always greener on the other side of >> > the >> > > > fence, especially after you've crossed it? >> > > > >> > > > Also, if I do my job properly, the language itself becomes irrelevant >> > and >> > > > the data structures are straightforward enough to allow any arbitrary >> > > > language to be used. >> > > > >> > > > (Meanwhile, I've got J running on OpenBSD, which pleases me.) >> > > > >> > > > -- >> > > > Raul >> > > > >> > > > Thanks, >> > > > >> > > > -- >> > > > Raul >> > > > >> > > > >> > > > On Tue, Apr 8, 2014 at 2:54 PM, km <[email protected]> wrote: >> > > > >> > > > > I think I would pay for k's database capability. --Kip Murray >> > > > > >> > > > > Sent from my iPad >> > > > > >> > > > > > On Apr 8, 2014, at 12:46 PM, Björn Helgason <[email protected]> >> > > wrote: >> > > > > > >> > > > > > I would take a look at the mapped file database lab to get ideas. >> > > > > > >> > > > > > - >> > > > > > Björn Helgason >> > > > > > gsm:6985532 >> > > > > > skype:gosiminn >> > > > > >> On 8.4.2014 15:34, "Raul Miller" <[email protected]> wrote: >> > > > > >> >> > > > > >> I have thought about using symbols, but the only way to delete >> > > symbols >> > > > > that >> > > > > >> I know of involves exiting J. And, my starting premise was that >> I >> > > > would >> > > > > >> have too much data to fit into memory. >> > > > > >> >> > > > > >> For some computations it does make sense to start up an >> > independent >> > > J >> > > > > >> session for each part of the calculation (and, in fact, that is >> > > what I >> > > > > am >> > > > > >> doing in a different aspect of dealing with this dataset - it's >> > > about >> > > > 10 >> > > > > >> terabytes, or so I am told - I've not actually seen it all yet >> and >> > > it >> > > > > takes >> > > > > >> time to upload it). But for some calculations you need to be >> able >> > to >> > > > > >> correlate between pieces which have been dealt with elsewhere. >> > > > > >> >> > > > > >> A have similar reservations about fixed-width fields. There's >> just >> > > too >> > > > > much >> > > > > >> data for me to predict how wide the fields are going to be. In >> > some >> > > > > cases I >> > > > > >> might actually be going with fixed-width, but that might be too >> > > > > inefficient >> > > > > >> for the general case. I've one field which would have to be over >> > > 100k >> > > > in >> > > > > >> width if it was fixed width, even though typical cases are >> shorter >> > > > than >> > > > > 1k. >> > > > > >> At some point I might go with fixed width, and I expect that >> doing >> > > so >> > > > > will >> > > > > >> cause me to lose a few records which will be discovered later in >> > > > > >> processing. That might not be a big deal, for this large of a >> data >> > > > set, >> > > > > but >> > > > > >> if it's not necessary why bother? >> > > > > >> >> > > > > >> Finally, Bjorn's suggestion of using mapped files does seem >> like a >> > > > good >> > > > > >> idea, at least for the character data. But that is an >> optimization >> > > and >> > > > > >> optimizations speed up some operations at the expense of slowing >> > > down >> > > > > other >> > > > > >> optimizations. So what really matters is the workload. >> > > > > >> >> > > > > >> Ultimately, for a dataset this large, it's going to take time. >> > > > > >> >> > > > > >> Thanks, >> > > > > >> >> > > > > >> -- >> > > > > >> Raul >> > > > > >> >> > > > > >> >> > > > > >> >> > > > > >> >> > > > > >>> On Tue, Apr 8, 2014 at 6:06 AM, Joe Bogner < >> [email protected]> >> > > > > wrote: >> > > > > >>> >> > > > > >>> It seems this representation is somewhat similar to how the >> > symbol >> > > > > table >> > > > > >>> stores strings: >> > > > > >>> >> > > > > >>> http://m.jsoftware.com/help/dictionary/dsco.htm >> > > > > >>> >> > > > > >>> Also, did you consider using symbols? I've used symbols for >> > string >> > > > > >> columns >> > > > > >>> that contain highly repetitive data, for example, an invoice >> > table >> > > > with >> > > > > >> an >> > > > > >>> alpha-numeric SKU. >> > > > > >>> >> > > > > >>> Thanks for sharing >> > > > > >>> >> > > > > >>> >> > > > > >>> >> > > > > >>> >> > > > > >>> >> > > > > >>> >> > > > > >>> On Tue, Apr 8, 2014 at 2:40 AM, Raul Miller < >> > [email protected] >> > > > >> > > > > >> wrote: >> > > > > >>> >> > > > > >>>> Consider this example: >> > > > > >>>> >> > > > > >>>> table=:<;._2;._2]0 :0 >> > > > > >>>> First Name,Last Name,Sum, >> > > > > >>>> Adam,Wallace,19, >> > > > > >>>> Travis,Smith,10, >> > > > > >>>> Donald,Barnell,8, >> > > > > >>>> Gary,Wallace,27, >> > > > > >>>> James,Smith,10, >> > > > > >>>> Sam,Johnson,10, >> > > > > >>>> Travis,Neal,11, >> > > > > >>>> Adam,Campbell,11, >> > > > > >>>> Walter,Abbott,13, >> > > > > >>>> ) >> > > > > >>>> >> > > > > >>>> Using boxed strings works great for relatively small sets of >> > data. >> > > > But >> > > > > >>> when >> > > > > >>>> things get big, their overhead starts to hurt to much. (Big >> > > means: >> > > > so >> > > > > >>> much >> > > > > >>>> data that you'll probably not be able to fit it all in memory >> at >> > > the >> > > > > >> same >> > > > > >>>> time. So you need to plan on relatively frequent delays while >> > > > reading >> > > > > >>> from >> > > > > >>>> disk.) >> > > > > >>>> >> > > > > >>>> One alternative to boxed strings is segmented strings. A >> > segmented >> > > > > >> string >> > > > > >>>> is an argument which could be passed to <;._1. It's basically >> > > just a >> > > > > >>> string >> > > > > >>>> with a prefix delimiter. You can work with these sorts of >> > strings >> > > > > >>> directly, >> > > > > >>>> and achieve results similar to what you would achieve with >> boxed >> > > > > >> arrays. >> > > > > >>>> >> > > > > >>>> Segmented strings are a bit clumsier than boxed arrays - you >> > lose >> > > a >> > > > > lot >> > > > > >>> of >> > > > > >>>> the integrity checks, so if you mess up you probably will not >> > see >> > > an >> > > > > >>> error. >> > > > > >>>> So it's probably a good idea to model your code using boxed >> > arrays >> > > > on >> > > > > a >> > > > > >>>> small set of data and then convert to segmented representation >> > > once >> > > > > >>> you're >> > > > > >>>> happy with how things work (and once you see a time cost that >> > > makes >> > > > it >> > > > > >>>> worth spending the time to rework your code). >> > > > > >>>> >> > > > > >>>> Also, to avoid having to use f;._2 (or whatever) every time, >> > it's >> > > > good >> > > > > >> to >> > > > > >>>> do an initial pass on the data, to extract its structure. >> > > > > >>>> >> > > > > >>>> Here's an example: >> > > > > >>>> >> > > > > >>>> FirstName=:;LF&,each }.0{"1 table >> > > > > >>>> >> > > > > >>>> LastName=:;LF&,each }.1{"1 table >> > > > > >>>> >> > > > > >>>> Sum=:;LF&,each }.2{"1 table >> > > > > >>>> >> > > > > >>>> >> > > > > >>>> ssdir=: [:(}:,:2-~/\])I.@(= {.),# >> > > > > >>>> >> > > > > >>>> FirstNameDir=: ssdir FirstName >> > > > > >>>> LastNameDir=: ssdir LastName >> > > > > >>>> >> > > > > >>>> Actually, sum is numeric so let's just use a numeric >> > > representation >> > > > > for >> > > > > >>>> that column >> > > > > >>>> >> > > > > >>>> Sum=: _&".@> }.2{"1 table >> > > > > >>>> >> > > > > >>>> Which rows have a last name of Smith? >> > > > > >>>> >> > > > > >>>> <:({.LastNameDir) I. I.'Smith' E. LastName >> > > > > >>>> >> > > > > >>>> 1 4 >> > > > > >>>> >> > > > > >>>> >> > > > > >>>> Actually, there's an assumption there that Smith is not part >> of >> > > some >> > > > > >>> larger >> > > > > >>>> name. We can include the delimiter in the search if we are >> > > concerned >> > > > > >>> about >> > > > > >>>> that. For even more protection we could append a trailing >> > > delimiter >> > > > on >> > > > > >>> our >> > > > > >>>> segmented string and then search for (in this case) >> > LF,'Smith',LF. >> > > > > >>>> >> > > > > >>>> >> > > > > >>>> Anyways, let's extract the corresponding sums and first name: >> > > > > >>>> >> > > > > >>>> >> > > > > >>>> 1 4{Sum >> > > > > >>>> >> > > > > >>>> 10 10 >> > > > > >>>> >> > > > > >>>> >> > > > > >>>> FirstName{~;<@(+ i.)/"1|:1 4 {"1 FirstNameDir >> > > > > >>>> >> > > > > >>>> >> > > > > >>>> Travis >> > > > > >>>> >> > > > > >>>> James >> > > > > >>>> >> > > > > >>>> >> > > > > >>>> Note that that last expression is a bit complicated. It's not >> so >> > > > bad, >> > > > > >>>> though, if what you are extracting is a small part of the >> total. >> > > > And, >> > > > > >> in >> > > > > >>>> that case, using a list of indices to express a boolean result >> > > seems >> > > > > >>> like a >> > > > > >>>> good thing. You wind up working with set operations >> > (intersection >> > > > and >> > > > > >>>> union) rather than logical operations (and and or). Also, set >> > > > > >> difference >> > > > > >>>> instead of logical not (dyadic -. instead of monadic -.). >> > > > > >>>> >> > > > > >>>> >> > > > > >>>> intersect=: [ -. -. >> > > > > >>>> >> > > > > >>>> union=. ~.@, >> > > > > >>>> >> > > > > >>>> >> > > > > >>>> (It looks like I might be using this kind of thing really >> soon, >> > > so I >> > > > > >>>> thought I'd lay down my thoughts here and invite comment.) >> > > > > >>>> >> > > > > >>>> >> > > > > >>>> Thanks, >> > > > > >>>> >> > > > > >>>> >> > > > > >>>> -- >> > > > > >>>> >> > > > > >>>> Raul >> > > > > >>>> >> > > > >> ---------------------------------------------------------------------- >> > > > > >>>> For information about J forums see >> > > > > http://www.jsoftware.com/forums.htm >> > > > > >>>> >> > > > > >>> >> > > > >> ---------------------------------------------------------------------- >> > > > > >>> For information about J forums see >> > > > http://www.jsoftware.com/forums.htm >> > > > > >>> >> > > > > >> >> > > ---------------------------------------------------------------------- >> > > > > >> For information about J forums see >> > > > http://www.jsoftware.com/forums.htm >> > > > > >> >> > > > > > >> > > ---------------------------------------------------------------------- >> > > > > > For information about J forums see >> > > http://www.jsoftware.com/forums.htm >> > > > > >> > ---------------------------------------------------------------------- >> > > > > For information about J forums see >> > http://www.jsoftware.com/forums.htm >> > > > > >> > > > >> ---------------------------------------------------------------------- >> > > > For information about J forums see >> http://www.jsoftware.com/forums.htm >> > > > >> > > ---------------------------------------------------------------------- >> > > For information about J forums see http://www.jsoftware.com/forums.htm >> > > >> > ---------------------------------------------------------------------- >> > For information about J forums see http://www.jsoftware.com/forums.htm >> > >> > ---------------------------------------------------------------------- >> > For information about J forums see http://www.jsoftware.com/forums.htm >> > >> ---------------------------------------------------------------------- >> For information about J forums see http://www.jsoftware.com/forums.htm >> >> ---------------------------------------------------------------------- >> For information about J forums see http://www.jsoftware.com/forums.htm >> > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
