Hmm, the *for* comprehension yields a lazy sequence of results. So the penalty should only occur when one starts to use / evaluate the result. Using maps is a good idea. But I think you'll have to use another algorithm (not *for*) to get the random access you seek.
Frank could try a *clojure.set/intersection* to find common keys between the lists. then *order* and *map* / *merge* the 2 lists. Beyond that, I can't see a scenario where some iteration won't have to search the space for matching keys (which I think *clojure.set/intersection* does). A fair point all the same. Tim Washington Interruptsoftware.com <http://interruptsoftware.com> On Sun, Mar 9, 2014 at 12:13 PM, Moritz Ulrich <mor...@tarn-vedra.de> wrote: > I think it would be more efficient to read one of the inputs into a > map for random access instead of iterating it every time. > > On Sun, Mar 9, 2014 at 4:48 PM, Timothy Washington <twash...@gmail.com> > wrote: > > Hey Frank, > > > > Try opening up a repl, and running this for comprehension. > > > > (def user_textfile [[:id1 {:name 'Frank'}] [:id3 {:name 'Tim'}]]) > > (def user_database [[:id1 {:age 38}] [:id2 {:age 27}] [:id3 {:age 18}] > [:id4 > > {:age 60}]]) > > > > (for [i user_textfile > > j user_database > > :when (= (first i) (first j))] > > {(first i) (merge (second i) (second j))}) > > > > ({:id1 {:age 38, :name Frank'}} {:id3 {:age 18, :name Tim'}}) ;; result > > from repl > > > > > > > > Hth > > > > Tim Washington > > Interruptsoftware.com > > > > > > On Sun, Mar 9, 2014 at 5:33 AM, Frank Behrens <fbehr...@gmail.com> > wrote: > >> > >> Hi, > >> > >> i'm investigating if clojure can be used to solve the challenges and > >> problems we have at my day job better than ruby or powershell. A very > common > >> use case is validating data from different systems against some > criteria. i > >> believe clojure can be our silver bullet, but before that, it seems to > be > >> required to wrap my head around it. > >> > >> So I am starting in the first level with the challenge to validate some > >> data from the user database against our active directory. > >> > >> I already have all the parts to make it work: Which is to make a hash by > >> user_id from the database table, export a textfile from AD, each line > >> representing a user, parse it, merge the information from the > >> user_table_hash, and voila. > >> > >> I did not finish to implement this. So I don't know if this naive > approach > >> will work with 400.000 records in the user database and 100.000 in the > >> textfile. > >> But I already think about how I could implement this in a more memory > >> efficient way. > >> > >> So my simple question: > >> > >> I have user_textfile (100.000 records) which can be parsed into a > >> unordered list of user-maps. > >> I have user_table in the database(400.000 record) which I can query with > >> order and gives me an ordered list of user-maps. > >> > >> So I would first order the user_textfile and then conj the user_table > >> ordered list into it, while doing the database query. > >> Is that approach right ? How would I then merge the two ordered lists > like > >> in the example below? > >> > >> (defn user_textfile > >> ([:id1 {:name 'Frank'}] > >> [:id3 {:name 'Tim'}])) > >> > >> (defn user_database > >> ([:id1 {:age 38}] > >> [:id2 {:age 27}] > >> [:id3 {:age 18}] > >> [:id4 {:age 60}])) > >> > >> (merge-sorted-lists user_database user_textfile) > >> => > >> ([:id1 {:name 'Frank' :age 38}] > >> [:id3 {:name 'Tim' :age 18}])) > >> > >> Any feedback is appreciated. > >> Have a nice day, > >> Frank > >> > >> -- > >> You received this message because you are subscribed to the Google > >> Groups "Clojure" group. > >> To post to this group, send email to clojure@googlegroups.com > >> Note that posts from new members are moderated - please be patient with > >> your first post. > >> To unsubscribe from this group, send email to > >> clojure+unsubscr...@googlegroups.com > >> For more options, visit this group at > >> http://groups.google.com/group/clojure?hl=en > >> --- > >> You received this message because you are subscribed to the Google > Groups > >> "Clojure" group. > >> To unsubscribe from this group and stop receiving emails from it, send > an > >> email to clojure+unsubscr...@googlegroups.com. > >> For more options, visit https://groups.google.com/d/optout. > > > > > > -- > > You received this message because you are subscribed to the Google > > Groups "Clojure" group. > > To post to this group, send email to clojure@googlegroups.com > > Note that posts from new members are moderated - please be patient with > your > > first post. > > To unsubscribe from this group, send email to > > clojure+unsubscr...@googlegroups.com > > For more options, visit this group at > > http://groups.google.com/group/clojure?hl=en > > --- > > You received this message because you are subscribed to the Google Groups > > "Clojure" group. > > To unsubscribe from this group and stop receiving emails from it, send an > > email to clojure+unsubscr...@googlegroups.com. > > For more options, visit https://groups.google.com/d/optout. > > -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
