sql - a proper way to escape %% when building LIKE queries in Rails 3 / ActiveRecord -


i want match url field against url prefix (which may contain percent signs), e.g. .where("url ?", "#{some_url}%"). what's rails way?

if understand correctly, you're worried "%" appearing inside some_url , rightly so; should worried embedded underscores ("_") too, they're version of "." in regex. don't think there rails-specific way of doing you're left gsub:

.where('url ?', some_url.gsub('%', '\\\\\%').gsub('_', '\\\\\_') + '%')

there's no need string interpolation here either. need double backslashes escape meaning database's string parser parser see simple "\%" , know ignore escaped percent sign.

you should check logs make sure 2 backslashes through. i'm getting confusing results checking things in irb, using 5 (!) gets right output don't see sense in it; if see sense in 5 of them, explanatory comment appreciated.

update: jason king has kindly offered simplification nightmare of escaped escape characters. lets specify temporary escape character can things this:

.where("url ? escape '!'", some_url.gsub(/[!%_]/) { |x| '!' + x })

i've switched block form of gsub make bit less nasty.

this standard sql92 syntax, work in db supports that, including postgresql, mysql , sqlite.

embedding 1 language inside bit of nightmarish kludge , there's not can it. there ugly little bits have grin , bear.


Comments

Post a Comment

Popular posts from this blog

authentication - Mongodb revoke acccess to connect test database -

i have ec2 instance mongodb 3.2.0 installed. have user admin access. can connect user , perform operation remotely. 1 can connect database test remote if knows ip mongo 11.11.11.11. although not able make operations, want restrict access user credentials can connect server. first need create users , grant roles users, example: use admin db.createuser( { user: "myuseradmin", pwd: "abc123", roles: [ { role: "useradminanydatabase", db: "admin" } ] } ) then need start server --auth parameter mongod --auth more information here
Read more

r - Update two sets of radiobuttons reactively - shiny -

i have read ( how make choices in radiobuttons reactive in shiny? ) shows me how update radiobutton s in reactive way. however, when try , update 2 sets of buttons same data, 1 set renders. example: server: # create example data wafer <- rep(c(1:3), each=3) length <- c(1,1,2,1,1,1,3,5,1) width <- c(3,1,6,1,1,1,1,1,6) dd <- data.frame(wafer, length, width) shinyserver(function(input, output, session){ # create reactive dataframe store data values <- reactivevalues() values$df <- data.frame() # lengths , widths of wafer user input <- eventreactive(input$do, { subset(dd, wafer %in% input$wafer, select = length:width) }) # update reactive data frame lengths , widths have been selected user input observe({ if(!is.null(a())) { values$df <- rbind(isolate(values$df), a()) } }) output$wl <- renderdatatable({ a() }) # update radio buttons unique length , widths stored in values$df # ever "observe" put first in co...
Read more

ios - Realm over CoreData should I use NSFetchedResultController or a Dictionary? -

i'm working on app using core data , nsfetchedresultcontroller many reasons switch use realm. saw there "realm version" of nsfetchedresultcontroller on github wouldn't compatible current code using core data. the view controller displaying list of people same school, address book. list sublist of people studied in same city. so thinking make 1 unique request database retrieve list of people , filter locally list within 1 dictionary per school [string: anyobject] string section name within tableview , anyobject array of people. first solution, make nsfetchedresultcontroller each school predicate filtering location. delete actions etc.. handled delegates -> not compatible realm create dictionaries , update them each actions... -> works realm it's annoying code. any better solution? edit: i need clarify request: i'd write class inherit uitableviewcontroller. this class has list of people sorted in alphabetical order the tableview has ...
Read more