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• PHP - Database schema: version control, branching, migrations.

  - by Billiam

  I'm trying to come up with (or find) a reusable system for database schema versioning in php projects. There are a number of Rails-style migration projects available for php. http://code.google.com/p/mysql-php-migrations/ is a good example. It uses timestamps for migration files, which helps with conflicts between branches. General problem with this kind of system: When development branch A is checked out, and you want to check out branch B instead, B may have new migration files. This is fine, migrating to newer content is straight forward. If branch A has newer migration files, you would need to migrate downwards to the nearest shared patch. If branch A and B have significantly different code bases, you may have to migrate down even further. This may mean: Check out B, determine shared patch number, check out A, migrate downwards to this patch. This must be done from A since the actual applied patches are not available in B. Then, checkout branch B, and migrate to newest B patch. Reverse process again when going from B to A. Proposed system: When migrating upwards, instead of just storing the patch version, serialize the whole patch in database for later use, though I'd probably only need the down() method. When changing branches, compare patches that have been run to patches that are available in the destination branch. Determine nearest shared patch (or oldest difference, maybe) between db table of run patches and patches in destination branch by ID or hash. Could also look for new or missing patches that are buried under a number of shared patches between the two branches. Automatically merge down to the nearest shared patch, using the db table stored down() methods, and then merge up to the branche's latest patch. My question is: Is this system too crazy and/or fraught with consequences to bother developing? My experience with database schema versioning is limited to PHP autopatch, which is an up()-only system requiring filenames with sequential IDs.

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• nested form collection_select new value overwriting previous selected values

  - by bharath

  Nested form <%= nested_form_for(@bill) do |f| %> <p><%= f.link_to_add "Add Product", :bill_line_items %> </p> Partial of bill line items <%= javascript_include_tag 'bill'%> <%= f.hidden_field :bill_id %> <%- prices = Hash[Product.all.map{|p| [p.id, p.price]}].to_json %> <%= f.label :product_id %> <%= f.collection_select :product_id ,Product.all,:id,:name, :class => 'product', :prompt => "Select a Product", input_html: {data: {prices: prices}}%> <br/ > <%= f.label :price, "price"%> <%= f.text_field :price, :size=>20, :class =>"price" %><br/> bill.js jQuery(document).ready(function(){ jQuery('.product').change(function() { var product_id = jQuery(this).val(); var price = eval(jQuery(this).data("prices"))[product_id]; jQuery('.price').val(price); }); }); Rails 3.2 Issue: Second click on Add Product & on selecting the product When we select the second product the price of second product is overwriting on the price of the first selected product. Request help.

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• strange syntax error in python, version 2.6 and 3.1

  - by flow

  this may not be an earth-shattering deficiency of python, but i still wonder about the rationale behind the following behavior: when i run source = """ print( 'helo' ) if __name__ == '__main__': print( 'yeah!' ) #""" print( compile( source, '<whatever>', 'exec' ) ) i get :: File "<whatever>", line 6 # ^ SyntaxError: invalid syntax i can avoid this exception by (1) deleting the trailing #; (2) deleting or outcommenting the if __name__ == '__main__':\n print( 'yeah!' ) lines; (3) add a newline to very end of the source. moreover, if i have the source end without a trailing newline right behind the print( 'yeah!' ), the source will also compile without error. i could also reproduce this behavior with python 2.6, so it’s not new to the 3k series. i find this error to be highly irritating, all the more since when i put above source inside a file and execute it directly or have it imported, no error will occur—which is the expected behavior. a # (hash) outside a string literal should always represent the start of a (possibly empty) comment in a python source; moreover, the presence or absence of a if __name__ == '__main__' clause should not change the interpretation of a soure on a syntactical level. can anyone reproduce the above problem, and/or comment on the phenomenon? cheers

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• How can I track down "Template process failed: undef error" in Perl's Template Toolkit?

  - by swisstony

  I've moved a Perl CGI app from one web host to another. Everything's running fine except for Template Tookit which is giving the following error: "Template process failed: undef error - This shouldn't happen at /usr/lib/perl5/5.8.8/CGI/Carp.pm line 314." The templates are working fine on the other web host. I've set the DEBUG_ALL flag when creating the template object, but it doesn't provide any additional info about errors just loads of debug output. I can't post the template source as there's lots of client specific stuff in it. I've written a simple test template and that works okay. Just wondering if anyone had seen this error before or has any ideas on the quickest way to find a fix for it. EDIT: Here's a snippet of the code that loads and processes the template. my $vars = {}; $vars->{page_url} = $page_url; $vars->{info} = $info; $vars->{is_valid} = 0; $vars->{invalid_input} = 0; $vars->{is_warnings} = 0; $vars->{is_invalid_price} = 0; $vars->{output_from_proc} = $proc_output; ... my $file = 'clientTemplate.html'; #create ref to hash use Template::Constants qw( :debug ); my $template = Template->new( { DEBUG => DEBUG_SERVICE | DEBUG_CONTEXT | DEBUG_PROVIDER | DEBUG_PLUGINS | DEBUG_FILTERS | DEBUG_PARSER | DEBUG_DIRS, EVAL_PERL => 1, INCLUDE_PATH => [ '/home/perlstuff/templates', ], } ); $template->process( $file, $vars ) || die "Template process failed: ", $template->error(), "\n";

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• weighted matching algorithm in Perl

  - by srk

  Problem : We have equal number of men and women.each men has a preference score toward each woman. So do the woman for each man. each of the men and women have certain interests. Based on the interest we calculate the preference scores. So initially we have an input in a file having x columns. First column is the person(men/woman) id. id are nothing but 0.. n numbers.(first half are men and next half woman) the remaining x-1 columns will have the interests. these are integers too. now using this n by x-1 matrix... we have come up with a n by n/2 matrix. the new matrix has all men and woman as their rows and scores for opposite sex in columns. We have to sort the scores in descending order, also we need to know the id of person related to the scores after sorting. So here i wanted to use hash table. once we get the scores we need to make up pairs.. for which we need to follow some rules. My trouble is with the second matrix of n by n/2 that needs to give information of which man/woman has how much preference on a woman/man. I need these scores sorted so that i know who is the first preferred woman/man, 2nd preferred and so on for a man/woman. I hope to get good suggestions on the data structures i use.. I prefer php or perl. Thank you in advance

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• making arrays from tab-delimited text file column

  - by absolutenewbie

  I was wondering if anyone could help a desperate newbie with perl with the following question. I've been trying all day but with my perl book at work, I can't seem to anything relevant in google...or maybe am genuinely stupid with this. I have a file that looks something like the following: Bob April Bob April Bob March Mary August Robin December Robin April The output file I'm after is: Bob April April March Mary August Robin December April So that it lists each month in the order that it appears for each person. I tried making it into a hash but of course it wouldn't let me have duplicates so I thought I would like to have arrays for each name (in this example, Bob, Mary and Robin). I'm afraid to upload the code I've been trying to tweak because I know it'll be horribly wrong. I think I need to define(?) the array. Would this be correct? Any help would be greatly appreciated and I promise I will be studying more about perl in the meantime. Thank you for your time, patience and help. #!/usr/bin/perl -w while (<>) { chomp; if (defined $old_name) { $name=$1; $month=$2; if ($name eq $old_name) { $array{$month}++; } else { print "$old_name"; foreach (@array) { push (@array, $month); print "\t@array"; } print "\n"; @array=(); $array{$month}++; } } else { $name=$1; $month=$2; $array{month}++; } $old_name=$name; } print "$old_name"; foreach (@array) { push (@array, $month); print "\t@array"; } print "\n";

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• Installing applications OTA

  - by Ed Marty

  I have a system set up to download jad files on users' Blackberries, but it only works intermittently, and seemingly randomly. If the user clicks on the link within their BlackBerry browser, 95% of the time on the first try an error message will pop up saying there was an HTTP 500 error (which our server never returns). Viewing the details of this message within the blackberry browser, it says nothing but java.lang.nullpointerexception which, again, could not have come from our server (running apache/php). However, if the user clicks on the link a few more times, or navigates away and goes back to that page, it suddenly works. No change on the server, it just shows the application install screen. Unfortunately, this doesn't always work; sometimes the error 500 just keeps showing up. The link is rather long (containing an sha hash as a token as part of the URL), but I would think that a long URL would either always be broken or always work, not work intermittently. The link uses a php script to download the jad and cod files. Linking to the files directly rather than using the script seems to work more often (I haven't determined if that also ever has an error 500 or not), but I can't find any issues with the headers. The content type is set correctly and, like I said, if the headers were an issue, I'd think it would either always work or always break. Any clues?

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• Nested Object Forms not working as expected

  - by Craig Walker

  I'm trying to get a nested model forms view working. As far as I can tell I'm doing everything right, but it still does not work. I'm on Rails 3 beta 3. My models are as expected: class Recipe < ActiveRecord::Base has_many :ingredients, :dependent => :destroy accepts_nested_attributes_for :ingredients attr_accessible :name end class Ingredient < ActiveRecord::Base attr_accessible :name, :sort_order, :amount belongs_to :recipe end I can use Recipe.ingredients_attributes= as expected: recipe = Recipe.new recipe.ingredients_attributes = [ {:name=>"flour", :amount=>"1 cup"}, {:name=>"sugar", :amount=>"2 cups"}] recipe.ingredients.size # -> 2; ingredients contains expected instances However, I cannot create new object graphs using a hash of parameters as shown in the documentation: params = { :name => "test", :ingredients_attributes => [ {:name=>"flour", :amount=>"1 cup"}, {:name=>"sugar", :amount=>"2 cups"}] } recipe = Recipe.new(params) recipe.name # -> "test" recipe.ingredients # -> []; no ingredient instances in the collection Is there something I'm doing wrong here? Or is there a problem in the Rails 3 beta?

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• Extracting specific nodes from XML using XML::Twig

  - by pratz

  i was trying to extract a particular set of nodes from the following XML structure using XML::Twig, but have been stuck ever since. I need to extract the 'player' nodes from the following structure and do a string match/replace on each of these node values. <pep:record> <agency> <subrecord type="scout"> <isnum>123XXX (print)</isnum> <isnum>234YYY (mag)</isnum> </subrecord> <subrecord type="group"> </subrecord> </agency </record> I tried using the following code, but I get pointed to a hash reference rather than actual string. my $parser = XML::Twig->new(twig_handlers => { isnum => sub { print $_->text."::" }, }); foreach my $rec (split(/::/, $parser->parse($my_xml))) { if ($rec =~ m/print/) { ($print = $rec) =~ s/( \(print\))//; } elsif($rec =~ m/mag/) { ($mag = $rec) =~ s/( \(mag\))//; } }

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• jQuery Address - redirect after form submit

  - by Stian

  Hello all, I use jQuery and AJAX to load content from links and forms into a content div. In addition I use the Address plugin to enable the back button and refresh. On the server side I use Java and Spring MVC. Since I'm using jQuery Address and AJAX the only page that is directly loaded is "index.html". Everything else is loaded into a content div, and what page to load is specified in the hash, ie. "index.html#/users/add.html" will load "users/add.html". Now, "users/add.html" contains a form for creating a new user. When the form is submitted and everything went OK, the controller redirects to "users/index.html". The problem is that jQuery Address doesn't know about the redirect, so the url will remain "index.html#/users/add.html". And this is a problem when you refresh the page and then get sent back to the form, instead of the index page. Is there a way to fix this problem? Thanks, Stian

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• proper way to dynamically assign backbone.js view el

  - by kikuchiyo

  I would like to create two ( or more ) view instances, each with different el attributes, and have events bound to them via backbone.js view's events hash ( not through jQuery ). Getting events to trigger when all instantiations have the same el is easy: someView = Backbone.View.extend({ el: '#someDiv', events: { 'click': 'someFunction' }, someFunction: function(){ //Do something here } }); So far, if I assign el in the initialize function, and set events normally as follows, events do not trigger: someView = Backbone.View.extend({ events: { 'click': 'someFunction' }, initialize: function( options ){ this.el = options.el }, someFunction: function(){ //Do something here } }); My first instinct was to have el be a function that returns the string representation of the dom element of interest: someView = Backbone.View.extend({ el: function(){ return '#someDiv-' + this.someNumber }, events: { 'click': 'someFunction' }, initialize: function( options ){ this.someNumber = options.someNumber }, someFunction: function(){ //Do something here } }); However, this triggers someFunction x times if I have x instantiations of someView. Next I tried setting both the el and events attributes in initialize: someView = Backbone.View.extend({ initialize: function( options ){ this.el = options.el this.events = { 'click': 'someFunction' } }, someFunction: function(){ //Do something here } }); but this does not trigger events. At this point I'm pretty much fishing. Does anyone know how instantiate a backbone.js view with an el specific to that instance that has events that only trigger for that instance, and not other instances of the View?

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• Rails fields_for parameters for a has_many relation don't yield an Array in params

  - by user1289061

  I have a model Sensor with has_many and accepts_nested_attributes_for relationships to another model Watch. In a form to update a Sensor, I have something like the following <%= sensor_form.fields_for :watches do |watches_form| %> <%= watches_form.label :label %><br /> <%= watches_form.text_field :label %> <% end %> This is indended to allow editting of the already-created Watches belonging to a Sensor. This call spits form inputs as so: <input name="sensor[watches_attributes][0][label]" ... /> <input name="sensor[watches_attributes][0][id]" ... /> When this gets submitted, the params object in the Sensor controller gets an assoc like "sensor" => { "id"=>"1", "watches_attributes"=> { "0"=>{"id" => "1", "label" => "foo"}, "1"=>{"id" => "2", "label" => "bar"} } } For a has_many, accepts_nested_attributes_for update to work upon the @sensor.update_attributes call, it seems that that attributes key really must map to an Array. From what I've seen in the examples, the combination of has_many, accepts_nested_attributes_for, and sensor_form.fields_for should allow me to pass the resulting params object directly to @sensor.update_attributes and update each related object as intended. Instead the Sensor takes place, with no errors, but the Watch objects are not updated (since "watches_attributes" maps to a Hash instead of an Array?) Have I missed something?

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• Binding a date string parameter in an MS Access PDO query

  - by harryg

  I've made a PDO database class which I use to run queries on an MS Access database. When querying using a date condition, as is common in SQL, dates are passed as a string. Access usually expects the date to be surrounded in hashes however. E.g. SELECT transactions.amount FROM transactions WHERE transactions.date = #2013-05-25#; If I where to run this query using PDO I might do the following. //instatiate pdo connection etc... resulting in a $db object $stmt = $db->prepare('SELECT transactions.amount FROM transactions WHERE transactions.date = #:mydate#;'); //prepare the query $stmt->bindValue('mydate', '2013-05-25', PDO::PARAM_STR); //bind the date as a string $stmt->execute(); //run it $result = $stmt->fetch(); //get the results As far as my understanding goes the statement that results from the above would look like this as binding a string results in it being surrounded by quotes: SELECT transactions.amount FROM transactions WHERE transactions.date = #'2013-05-25'#; This causes an error and prevents the statement from running. What's the best way to bind a date string in PDO without causing this error? I'm currently resorting to sprintf-ing the string which I'm sure is bad practise. Edit: if I pass the hash-surrounded date then I still get the error as below: Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[22018]: Invalid character value for cast specification: -3030 [Microsoft][ODBC Microsoft Access Driver] Data type mismatch in criteria expression. (SQLExecute[-3030] at ext\pdo_odbc\odbc_stmt.c:254)' in C:\xampp\htdocs\ips\php\classes.php:49 Stack trace: #0 C:\xampp\htdocs\ips\php\classes.php(49): PDOStatement-execute() #1 C:\xampp\htdocs\ips\php\classes.php(52): database-execute() #2 C:\xampp\htdocs\ips\try2.php(12): database-resultset() #3 {main} thrown in C:\xampp\htdocs\ips\php\classes.php on line 49

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• Objective-C Implementation Pointers

  - by Dwaine Bailey

  Hi, I am currently writing an XML parser that parses a lot of data, with a lot of different nodes (the XML isn't designed by me, and I have no control over the content...) Anyway, it currently takes an unacceptably long time to download and read in (about 13 seconds) and so I'm looking for ways to increase the efficiency of the read. I've written a function to create hash values, so that the program no longer has to do a lot of string comparison (just NSUInteger comparison), but this still isn't reducing the complexity of the read in... So I thought maybe I could create an array of IMPs so that, I could then go something like: for(int i = 0; i < [hashValues count]; i ++) { if(currHash == [[hashValues objectAtIndex:i] unsignedIntValue]) { [impArray objectAtIndex:i]; } } Or something like that. The only problem is that I don't know how to actually make the call to the IMP function? I've read that I perform the selector that an IMP defines by going IMP tImp = [impArray objectAtIndex:i]; tImp(self, @selector(methodName)); But, if I need to know the name of the selector anyway, what's the point? Can anybody help me out with what I want to do? Or even just some more ways to increase the efficiency of the parser...

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• PHP Encrypt/Decrypt with TripleDes, PKCS7, and ECB

  - by Brandon Green

  I've got my encryption function working properly however I cannot figure out how to get the decrypt function to give proper output. Here is my encrypt function: function Encrypt($data, $secret) { //Generate a key from a hash $key = md5(utf8_encode($secret), true); //Take first 8 bytes of $key and append them to the end of $key. $key .= substr($key, 0, 8); //Pad for PKCS7 $blockSize = mcrypt_get_block_size('tripledes', 'ecb'); $len = strlen($data); $pad = $blockSize - ($len % $blockSize); $data .= str_repeat(chr($pad), $pad); //Encrypt data $encData = mcrypt_encrypt('tripledes', $key, $data, 'ecb'); return base64_encode($encData); } Here is my decrypt function: function Decrypt($data, $secret) { $text = base64_decode($data); $data = mcrypt_decrypt('tripledes', $secret, $text, 'ecb'); $block = mcrypt_get_block_size('tripledes', 'ecb'); $pad = ord($data[($len = strlen($data)) - 1]); return substr($data, 0, strlen($data) - $pad); } Right now I am using a key of test and I'm trying to encrypt 1234567. I get the base64 output from encryption I'm looking for, but when I go to decrypt I get a blank response. I'm not very well versed in encryption/decryption so any help is much appreciated!!

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• A map and set which uses contiguous memory and has a reserve function

  - by edA-qa mort-ora-y

  I use several maps and sets. The lack of contiguous memory, and high number of (de)allocations, is a performance bottleneck. I need a mainly STL-compatbile map and set class which can use a contiguous block of memory for internal objects (or multiple blocks). It also needs to have a reserve function so that I can preallocate for expected sizes. Before I write my own I'd like to check what is available first. Is there something in Boost which does this? Does somebody know of an available implementation elsewhere? Intrusive collection types are not usable here as the same objects need to exist in several collections. As far as I know STL memory pools are per-type, not per instance. These global pools are not efficient with respect to memory locality in mutli-cpu/core processing. Object pools don't work as the types will be shared between instance but their pool should not. In many cases a hash map may be an option in some cases.

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• how do I paste text to a line by line text filter like awk, without having stdin echo to the screen?

  - by Barton Chittenden

  I have a text in an email on a windows box that looks something like this: 100 some random text 101 some more random text 102 lots of random text, all different 103 lots of random text, all the same I want to extract the numbers, i.e. the first word on each line. I've got a terminal running bash open on my Linux box... If these were in a text file, I would do this: awk '{print $1}' mytextfile.txt I would like to paste these in, and get my numbers out, without creating a temp file. my naive first attempt looked like this: $ awk '{print $1}' 100 some random text 100 101 some more random text 101 102 lots of random text, all different 103 lots of random text, all the same 102 103 The buffering of stdin and stdout make a hash of this. I wouldn't mind if stdin all printed first, followed by all of stdout; this is what would happen if I were to paste into 'sort' for example, but awk and sed are a different story. a little more thought gave me this: open two terminals. Create a fifo file. Read from the fifo on one terminal, write to it on another. This does in fact work, but I'm lazy. I don't want to open a second terminal. Is there a way in the shell that I can hide the text echoed to the screen when I'm passing it in to a pipe, so that I paste this: 100 some random text 101 some more random text 102 lots of random text, all different 103 lots of random text, all the same but see this? $ awk '{print $1}' 100 101 102 103

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• Join + IEqualityComparer<T> and HashCode

  - by Jesus Rodriguez

  Im writing my own LINQ reference but Im getting troubles with some of the more complicated operators implementations. There is a Join implementation that takes a IEqualityComparer Im getting just crazy. Im trying to understand it first before I write (obviously) Image this two lists: List<string> initials = new List<string> {"A", "B", "C", "D", "E"}; List<string> words = new List<string> {"Ant", "Crawl", "Pig", "Boat", "Elephant", "Arc"}; Nothing weird here. I want to join both lists by the Initial, something like: Initial=A Word=Ant Initial=A Word=Arc Initial=B Word=Boat ... I need a comparator, I wrote this: public class InitialComparator : IEqualityComparer<string> { public bool Equals(string x, string y) { return x.StartsWith(y); } public int GetHashCode(string obj) { return obj[0].GetHashCode(); } } The Join itself: var blah = initials.Join(words, initial => initial, word => word, (initial, word) => new {Initial = initial, Word = word}, new InitialComparator()); It's the first time Im using HashCodes, after a good session of debugging I see that every word go to the comparator and look at its HashCode, if another word has the same HashCode it calls equals. Since I want to compare just the initial I though that I just need the first letter Hash (Am I wrong?) The thing is that this is not working correctly. Its says that "Ant" and "Arc" are equals, Ok, its comparing every word in the same list or not, But it adds only the last word it finds, in this case Arc, ignoring Ant and Ant is equals to "A" too... If I put "Ant" and "Ant" it add both. In short, What is the way of doing something like that? I know that Im doing something wrong. Thank you.

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• .NET Hashtable - "Same" key, different hashes

  - by Simon Lindgren

  Is it possible for two .net strings to have different hashes? I have a Hashtable with amongst others the key "path". When I loop through the elements in the table to print it, i can see that the key exists. When trying to looking it up however, there is no matching element. Debugging suggests that the string I'm looking for has a different hash than the one I'm supplying as the key. This code is in a Castle Monorail project, using brail as a view engine. The key I'm looking for is inserted by a brail line like this: UrlHelper.Link(node.CurrentPage.LinkText, {@params: {@path: "/Page1"}}) Then, in this method (in a custom IRoutingRule): public string CreateUrl(System.Collections.IDictionary parameters) { PrintDictionaryToLog(parameters); string url; if (parameters.Contains("path")) { url = (string)parameters["path"]; } else { return null; } } The key is printed to the log, but the function returns null. I didn't know this could even be a problem with .net strings, but I guess this is some kind of encoding issue? Oh, and this is running mono.

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• Poor execution plans when using a filter and CONTAINSTABLE in a query

  - by Paul McLoughlin

  We have an interesting problem that I was hoping someone could help to shed some light on. At a high level the problem is as below: The following query executes quickly (1 second): SELECT SA.* FROM cg.SEARCHSERVER_ACTYS AS SA JOIN CONTAINSTABLE(CG.SEARCHSERVER_ACTYS, NOTE, 'reports') AS T1 ON T1.[Key]=SA.UNIQUE_ID but if we add a filter to the query, then it takes approximately 2 minutes to return: SELECT SA.* FROM cg.SEARCHSERVER_ACTYS AS SA JOIN CONTAINSTABLE(CG.SEARCHSERVER_ACTYS, NOTE, 'reports') AS T1 ON T1.[Key]=SA.UNIQUE_ID WHERE SA.CHG_DATE'19 Feb 2010' Looking at the execution plan for the two queries, I can see that in the second case there are two places where there are huge differences between the actual and estimated number of rows, these being: 1) For the FulltextMatch table valued function where the estimate is approx 22,000 rows and the actual is 29 million rows (which are then filtered down to 1670 rows before the join) and 2) For the index seek on the full text index, where the estimate is 1 row and the actual is 13,000 rows As a result of the estimates, the optimiser is choosing to use a nested loops join (since it assumes a small number of rows) hence the plan is inefficient. We can work around the problem by either (a) parameterising the query and adding an OPTION (OPTIMIZE FOR UNKNOWN) to the query or (b) by forcing a HASH JOIN to be used. In both of these cases the query returns in sub 1 second and the estimates appear reasonable. My question really is 'why are the estimates being used in the poorly performing case so wildly inaccurate and what can be done to improve them'? Statistics are up to date on the indexes on the indexed view being used here. Any help greatly appreciated.

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• Discover periodic patterns in a large data-set

  - by Miner

  I have a large sequence of tuples on disk in the form (t1, k1) (t2, k2) ... (tn, kn) ti is a monotonically increasing timestamp and ki is a key (assume a fixed length string if needed). Neither ti nor ki are guaranteed to be unique. However, the number of unique tis and kis is huge (millions). n itself is very large (100 Million+) and the size of k (approx 500 bytes) makes it impossible to store everything in memory. I would like to find out periodic occurrences of keys in this sequence. For example, if I have the sequence (1, a) (2, b) (3, c) (4, b) (5, a) (6, b) (7, d) (8, b) (9, a) (10, b) The algorithm should emit (a, 4) and (b, 2). That is a occurs with a period of 4 and b occurs with a period of 2. If I build a hash of all keys and store the average of the difference between consecutive timestamps of each key and a std deviation of the same, I might be able to make a pass, and report only the ones that have an acceptable std deviation(ideally, 0). However, it requires one bucket per unique key, whereas in practice, I might have very few really periodic patterns. Any better ways?

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• Literal ampersands in System.Uri query string

  - by Nathan Baulch

  I'm working on a client app that uses a restful service to look up companies by name. It's important that I'm able to include literal ampersands in my queries since this character is quite common in company names. However whenever I pass %26 (the URI escaped ampersand character) to System.Uri, it converts it back to a regular ampersand character! On closer inspection, the only two characters that aren't converted back are hash (%23) and percent (%25). Lets say I want to search for a company named "Pierce & Pierce": var endPoint = "http://localhost/companies?where=Name eq '{0}'"; var name = "Pierce & Pierce"; Console.WriteLine(new Uri(string.Format(endPoint, name))); Console.WriteLine(new Uri(string.Format(endPoint, Uri.EscapeUriString(name)))); Console.WriteLine(new Uri(string.Format(endPoint, Uri.EscapeDataString(name)))); All three of the above combinations return: http://localhost/companies?where=Name eq 'Pierce & Pierce' This causes errors on the server side since the ampersand is (correctly) interpreted as a query arg delimiter. What I really need it to return is the original string: http://localhost/companies?where=Name eq 'Pierce %26 Pierce' How can I work around this behavior without discarding System.Uri entirely? I can't replace all ampersands with %26 at the last moment because there will usually be multiple query args involved and I don't want to destroy their delimiters. Note: A similar problem was discussed in this question but I'm specifically referring to System.Uri.

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• Consistent Equals() results, but inconsistent TreeMap.containsKey() result

  - by smessing

  I have the following object Node: private class Node implements Comparable<Node>(){ private String guid(); ... public boolean equals(Node o){ return (this == o); } public int hashCode(){ return guid.hashCode(); } ... } And I use it in the following TreeMap: TreeMap<Node, TreeSet<Edge>> nodes = new TreeMap<Node, TreeSet<Edge>>(); Now, the tree map is used in a class called Graph to store nodes currently in the graph, along with a set of their edges (from the class Edge). My problem is when I try to execute: public containsNode(n){ for (Node x : nodes.keySet()) { System.out.println("HASH CODE: "); System.out.print(x.hashCode() == n.hashCode()); System.out.println("EQUALS: "); System.out.print(x.equals(n)); System.out.println("CONTAINS: "); System.out.print(nodes.containsKey(n)); System.out.println("N: " + n); System.out.println("X: " + x); } } I sometimes get the following: HASHCODE: true EQUALS: true CONTAINS: false N: foo X: foo Anyone have an idea as to what I'm doing wrong? I'm still new to all this, so I apologize in advance if I'm overlooking something simple (I know hashCode() doesn't really matter for TreeMap, but I figured I'd include it).

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• Storing Arbitrary Contact Information in Ruby on Rails

  - by Anthony Chivetta

  Hi, I am currently working on a Ruby on Rails app which will function in some ways like a site-specific social networking site. As part of this, each user on the site will have a profile where they can fill in their contact information (phone numbers, addresses, email addresses, employer, etc.). A simple solution to modeling this would be to have a database column per piece of information I allow users to enter. However, this seems arbitrary and limited. Further, to support allowing users to enter as many phone numbers as they would like requires the addition of another database table and joins. It seems to me that a better solution would be to serialize all the contact information entered by a user into a single field in their row. Since I will never be conditioning a SQL query on this information, such a solution wouldn't be any less efficient. Ideally, I would like to use a vCard as my serialization format. vCards are the standard solution to storing contact information across the web, and reusing tested solutions is a Good Thing. Alternative serialization formats would include simply marshaling a ruby hash, or YAML. Regardless of serialization format, supporting the reading and updating of this information in a rails-like way seems to be a major implementation challenge. So, here's the question: Has anyone seen this approach used in a rails application? Are there any rails plugins or gems that make such a system easy to implement? Ideally what I would like is an acts_as_vcard to add to my model object that would handle editing the vcard for me and saving it back to the database.

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• Is there a Boost (or other common lib) type for matrices with string keys?

  - by mohawkjohn

  I have a dense matrix where the indices correspond to genes. While gene identifiers are often integers, they are not contiguous integers. They could be strings instead, too. I suppose I could use a boost sparse matrix of some sort with integer keys, and it wouldn't matter if they're contiguous. Or would this still occupy a great deal of space, particularly if some genes have identifiers that are nine digits? Further, I am concerned that sparse storage is not appropriate, since this is an all-by-all matrix (there will be a distance in each and every cell, provided the gene exists). I'm unlikely to need to perform any matrix operations (e.g., matrix multiplication). I will need to pull vectors out of the matrix (slices). It seems like the best type of matrix would be keyed by a Boost unordered_map (a hash map), or perhaps even simply an STL map. Am I looking at this the wrong way? Do I really need to roll my own? I thought I saw such a class somewhere before. Thanks!

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