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• How to design data storage for partitioned tagging system?

  - by Morgan Cheng

  How to design data storage for huge tagging system (like digg or delicious)? There is already discussion about it, but it is about centralized database. Since the data is supposed to grow, we'll need to partition the data into multiple shards soon or later. So, the question turns to be: How to design data storage for partitioned tagging system? The tagging system basically has 3 tables: Item (item_id, item_content) Tag (tag_id, tag_title) TagMapping(map_id, tag_id, item_id) That works fine for finding all items for given tag and finding all tags for given item, if the table is stored in one database instance. If we need to partition the data into multiple database instances, it is not that easy. For table Item, we can partition its content with its key item_id. For table Tag, we can partition its content with its key tag_id. For example, we want to partition table Tag into K databases. We can simply choose number (tag_id % K) database to store given tag. But, how to partition table TagMapping? The TagMapping table represents the many-to-many relationship. I can only image to have duplication. That is, same content of TagMappping has two copies. One is partitioned with tag_id and the other is partitioned with item_id. In scenario to find tags for given item, we use partition with tag_id. If scenario to find items for given tag, we use partition with item_id. As a result, there is data redundancy. And, the application level should keep the consistency of all tables. It looks hard. Is there any better solution to solve this many-to-many partition problem?

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• How can I go through a Set in JSP? (Hibernate Associations)

  - by Parris

  Hi All, So I am pretty new to JSP. I have tried this a few ways. Ways that would make sense in PHP or automagicy frameworks... I am probably thinking too much in fact... I have a hibernate one to many association. That is class x has many of class y. In class x's view.jsp. I would like to grab all of class y, where the foreign key of y matches the primary key of x and display them. It seems that hibernate properly puts this stuff into a set. Now, the question is how can I iterate through this set and then output it's contents... I am kind of stumped here. I tried to write a scriptlet, <% java.util.Iterator iter = aBean.getYs().iter(); // aBeans is the bean name // getYs would return the set and iter would return an iterator for the set while(iter.hasNext) { model.X a = new iter.next() %> <h1><%=a.getTitle()%></h1> <% } %> It would seem that that sort of thing should work? Hmmmmmm

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• Fluent NHibernate AutoMap

  - by Markus

  Hi. I have a qouestion regarding the AutoMap xml generation. I have two classes: public class User { virtual public Guid Id { get; private set; } virtual public String Name { get; set; } virtual public String Email { get; set; } virtual public String Password { get; set; } virtual public IList<OpenID> OpenIDs { get; set; } } public class OpenID { virtual public Guid Id { get; private set; } virtual public String Provider { get; set; } virtual public String Ticket { get; set; } virtual public User User { get; set; } } The generated sequences of xml files are: For User class: <bag name="OpenIDs"> <key> <column name="User_Id" /> </key> <one-to-many class="BL_DAL.Entities.OpenID, BL_DAL, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" /> </bag> For OpenID class: <many-to-one class="BL_DAL.Entities.User, BL_DAL, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" name="User"> <column name="User_id" /> </many-to-one> I don't see the inverse=true attribute for the User mapping. Is it a normal behavior, or I made a mistake somewhere?

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• get_post_meta return empty string

  - by Jean-philippe Emond

  I guest it is a little issues but I running a SQL to get some post id. $result = $wpdb->get_results("SELECT wppm.post_id FROM wp_postmeta wppm INNER JOIN wp_posts wpp ON wppm.post_id=wpp.ID WHERE wppm.meta_key LIKE 'activity'"); (count: 302) After that, I get all id and I run get_post_meta like that: foreach($result as $id){ $activity = get_post_meta($id); var_dump($activity); foreach($activity as $key=>$value){ if(is_array($value) && $key=="age"){ var_dump($value); } } } (var_dump result: string "") samething if I run with: $activity = get_post_meta($id,'activity',true); Where we need to get a result. What is wrong? Thank you for your help!!! [Bonus Question] If the "activity" meta_key as an array Value. and I get directly like: $result = $wpdb->get_results("SELECT wppm.meta_value FROM wp_postmeta wppm INNER JOIN wp_posts wpp ON wppm.post_id=wpp.ID WHERE wppm.meta_key LIKE 'activity'"); How I parse it? Thanks again!

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• How to map a 0..1 to 1 relationship in Entity Framework 3

  - by sako73

  I have two tables, Users, and Address. A the user table has a field that maps to the primary key of the address table. This field can be null. In plain english, Address exist independent of other objects. A user may be associated with one address. In the database, I have this set up as a foreign key relationship. I am attempting to map this relationship in the Entity Framework. I am getting errors on the following code: <Association Name="fk_UserAddress"> <End Role="User" Type="GenesisEntityModel.Store.User" Multiplicity="1"/> <End Role="Address" Type="GenesisEntityModel.Store.Address" Multiplicity="0..1" /> <ReferentialConstraint> <Principal Role="Address"> <PropertyRef Name="addressId"/> </Principal> <Dependent Role="User"> <PropertyRef Name="addressId"/> </Dependent> </ReferentialConstraint> </Association> It is giving a "The Lower Bound of the multiplicity must be 0" error. I would appreciate it if anyone could explain the error, and the best way to solve it. Thanks for any help.

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• How to store and compare time-zone sensitive times

  - by Chad Moran

  I have a data structure where an entity has times stored as an int (minutes into the day) for fast comparison. The entity also has a Foreign Key reference back to a TimeZone table which contains the .NET CLR ID Name and it's Standard Time/Daylight Time acronyms. Since this information is stored as time-zone insensitive - I was wondering how in LINQ to SQL I could convert this into a UTC DateTime for comparison against other times that will be in UTC. Just to be clear this conversion has to be done server-side so that I can execute filtering on the SQL Server and not the client. I am using .NET 3.5 SP1 and SQL Server 2008.

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• Is there a JavaScript event that fires when a tab index switch is triggered? (TABINDEX does not work for inputs in IFRAME)

  - by treeface

  My specific use case is that I have a WYSIWYG editor which is basically an editable iframe. To the user, however, it looks like a standard-issue textarea. My problem is that I have inputs that sit before and after this editor in the (perceived) tab index and I'd like the user to be able to press tab (or the equivalent on his platform of choice) to get to the WYSIWYG editor when he's in the previous element and shift-tab to get to it when he's in the latter element. I know this can be faked using the key events and checking whether or not the tab key was pressed, but I'm curious if there's a better way. UPDATE. treeface clarified the actual problem in the comments. PROBLEM: In normal case, you can use "TABINDEX" attribute of the <input> element to control that, when tabbing out of "Subject" input field (in an email form), the focus lands on "Body" input field in the e-mail. This is done simply by assigning correctly ordered values to "TABINDEX" attribute of both input fields. The problem is that TABINDEX attribute only orders elements within the same frame. So, if "Body" input field is actually in an internal IFRAME, you can't tab out of "Subject" in the parent frame straight into "Body" in the IFRAME using TABINDEX order.

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• nhibernate mapping: delete collection, insert new collection with old IDs

  - by npeBeg

  my issue lokks similar to this one: (link) but i have one-to-many association: <set name="Fields" cascade="all-delete-orphan" lazy="false" inverse="true"> <key column="[TEMPLATE_ID]"></key> <one-to-many class="MyNamespace.Field, MyLibrary"/> </set> (i also tried to use ) this mapping is for Template object. this one and the Field object has their ID generators set to identity. so when i call session.Update for the Template object it works fine, well, almost: if the Field object has an Id number, UPDATE sql request is called, if the Id is 0, the INSERT is performed. But if i delete a Field object from the collection it has no effect for the Database. I found that if i also call session.Delete for this Field object, everything will be ok, but due to client-server architecture i don't know what to delete. so i decided to delete all the collection elements from the DB and call session.Update with a new collection. and i've got an issue: nhibernate performs the UPDATE operation for the Field objects that has non-zero Id, but they are removed from DB! maybe i should use some other Id generator or smth.. what is the best way to make nhibernate perform "delete all"/"insert all" routine for the collection?

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• How Optimize sql query make it faster

  - by user502083

  Hello every one : I have a very simple small database, 2 of tables are: Node (Node_ID, Node_name, Node_Date) : Node_ID is primary key Citation (Origin_Id, Target_Id) : PRIMARY KEY (Origin_Id, Target_Id) each is FK in Node Now I write a query that first find all citations that their Origin_Id has a specific date and then I want to know what are the target dates of these records. I'm using sqlite in python the Node table has 3000 record and Citation has 9000 records, and my query is like this in a function: def cited_years_list(self, date): c=self.cur try: c.execute("""select n.Node_Date,count(*) from Node n INNER JOIN (select c.Origin_Id AS Origin_Id, c.Target_Id AS Target_Id, n.Node_Date AS Date from CITATION c INNER JOIN NODE n ON c.Origin_Id=n.Node_Id where CAST(n.Node_Date as INT)={0}) VW ON VW.Target_Id=n.Node_Id GROUP BY n.Node_Date;""".format(date)) cited_years=c.fetchall() self.conn.commit() print('Cited Years are : \n ',str(cited_years)) except Exception as e: print('Cited Years retrival failed ',e) return cited_years Then I call this function for some specific years, But it's crazy slowwwwwwwww :( (around 1 min for a specific year) Although my query works fine, it is slow. would you please give me a suggestion to make it faster? I'd appreciate any idea about optimizing this query :) I also should mention that I have indices on Origin_Id and Target_Id, so the inner join should be pretty fast, but it's not!!!

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• Fulltext for innoDB? or a good solution for php app

  - by Joshua

  I have a table I want to run a fulltext search on, but it is currently innoDB and is using a lot of foreign keys for other kinds of queries. Should I make like a 1:1 "meta-data" table that is myisam for fulltext? Also I am reading some things that say that fulltext corrupts MySQL tables pretty randomly? I dunno, the articles are a couple years old, maybe they've fixed that in 5+? If not what's a good solution for searching? Zend_Lucene seems cool but slow, even with caching, for the client's large tables and autocomplete functionality et al.

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• How to display multiple categories and products underneath each category?

  - by shin

  Generally there is a category menu and each link to a category page where shows all the items under that category. Now I need to show all the categories and products underneath with PHP/MySQL in the same page. So it will be like this. Category 1 description of category 1 item 1 item 2 .. Category 2 description of category 2 item 5 item 6 .. Category 3 description of category 3 item 8 item 9 ... ... I have category and product table in my database. But I am not sure how to proceed. CREATE TABLE IF NOT EXISTS `omc_product` ( `id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(255) NOT NULL, `shortdesc` varchar(255) NOT NULL, `longdesc` text NOT NULL, `thumbnail` varchar(255) NOT NULL, `image` varchar(255) NOT NULL, `product_order` int(11) DEFAULT NULL, `class` varchar(255) DEFAULT NULL, `grouping` varchar(16) DEFAULT NULL, `status` enum('active','inactive') NOT NULL, `category_id` int(11) NOT NULL, `featured` enum('none','front','webshop') NOT NULL, `other_feature` enum('none','most sold','new product') NOT NULL, `price` float(7,2) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=2 ; CREATE TABLE IF NOT EXISTS `omc_category` ( `id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(255) NOT NULL, `shortdesc` varchar(255) NOT NULL, `longdesc` text NOT NULL, `status` enum('active','inactive') NOT NULL, `parentid` int(11) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=2 ; I will appreciate your help. Thanks in advance.

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• SQLAlchemy Mapping problem

  - by asdvalkn

  Dear Everyone, I am trying to sqlalchemy to correctly map my data. Note that a unified group is basically a group of groups. (One unifiedGroup maps to many groups but each group can only map to one ug). So basically this is the definition of my unifiedGroups: CREATE TABLE `unifiedGroups` ( `ugID` INT AUTO_INCREMENT, `gID` INT NOT NULL, PRIMARY KEY(`ugID`, `gID`), KEY( `gID`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 ; Note that each row is a ugID, gID tuple. ( I do not know before hand how many gID is per ugID so this is probably the most sensible and simplest method). Definition for my UnifiedGroup class class UnifiedGroup(object): """UnifiedProduct behaves very much like a group """ def __init__(self, ugID): self.ugID=ugID #Added by mapping self.groups=False def __str__(self): return '<%s:%s>' % (self.ugID, ','.join( [g for g in self.groups])) These are my mapping tables: tb_groupsInfo = Table( 'groupsInfo', metadata, Column('gID', Integer, primary_key=True), Column('gName', String(128)), ) tb_unifiedGroups = Table( 'unifiedGroups', metadata, Column('ugID', Integer, primary_key=True), Column('gID', Integer, ForeignKey('groupsInfo.gID')), ) My mapper maps in the following manner: mapper( UnifiedGroup, tb_unifiedGroups, properties={ 'groups': relation( Group, backref='unifiedGroup') }) However, when I tried to do groupInstance.unifiedGroup, I am getting an empty list [], while groupInstance.unifiedGroup.groups returns me an error: AttributeError: 'InstrumentedList' object has no attribute 'groups' Traceback (most recent call last): File "Mapping.py", line 119, in <module> print p.group.unifiedGroup.groups AttributeError: 'InstrumentedList' object has no attribute 'groups' What is wrong?

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• global security manager in flex

  - by ron

  hi, I made a swf that interacts with other site on the internet (which has a crossdomainfile for me). in the main.mxml there is a definition of webservice (mx:WebService)(which is not in my domain). Therefore when loading the swf, there is a first call to crossdomainfile.xml. I put this swf on my server so that my clients can get it. When i connect to my server to download the swf, i expect to be asked if i want to allow the swf connect to foreign webservice domain. But i am not being asked. Do i always need to define exception in Global Security Settings panel? I don't want my client do define special things.. Is there a best practice for that? Why when i surfing the net other swf can do this? I read about the FlashPlayerTrust, can i define there a website i trust my swf will connect to? anyone knows?

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• Importing Excel spreadsheet data into existing Access DB

  - by Keeb13r

  I've designed an Access 2003 DB with 3 tables: APPLICATIONS, SERVERS, and INSTALLATIONS. Records in the APPLICATIONS and SERVERS tables are uniquely identified by a synthetic primary key (in Access, an "auto number"). The INSTALLATIONS table is essentially a mapping table between APPLICATIONS and SERVERS: it's a list of records of which applications are installed on which servers. A record in the INSTALLATIONS table is also identified by a synthetic primary key, and it consists of an APPLICATION_ID and SERVER_ID for the records in their respective tables. I have an Excel 2003 spreadsheet I would like to import into this database, but it's proving difficult. The spreadsheet is made up of several tabs/worksheets, each one representing a server with its own listing of installed applications. I'm not sure how to proceed with an import - the "Get External Data -- Import" feature in Access has an import "In an Existing Table" option, but it's greyed out. I'm also unsure how I build the relationships between applications and servers for importing records into the INSTALLATIONS table. I had previously fooled around with adding some security to the Access DB file. I think I removed everything but perhaps I didn't and that's causing the problem? Some sample data from the Excel spreadsheet: SERVER101 * Adobe Reader 9 * BMC Remedy User 7.0 * HostExplorer 2008 * Microsoft Office 2003 * Microsoft Office 2007 * Notepad++ SERVER102 * Adobe Reader 9 * DameWare Mini Remote Control * Microsoft Office 2003 * Microsoft .NET Framework 3.5 SP1 * Oracle 9.2 SERVER103 * AWDView * EXTRA! Personal Client 32-bit * Microsoft Office 2003 * Microsoft .NET Framework 3.5 SP1 * Snagit 9.1 * WinZip 12.1 The Access DB design is very simple: APPLICATION * APPLICATION_ID (autonumber) * APPLICATION_NAME (varchar) SERVER * SERVER_ID (autonumber) * SERVER_NAME (varchar) INSTALLATION * INSTALLATION_ID (autonumber) * APPLICATION_ID (number) * SERVER_ID (number)

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• Why does my jQuery/YQL call not return anything?

  - by tastyapple

  I'm trying to access YQL with jQuery but am not getting a response: http://jsfiddle.net/tastyapple/grMb3/ Anyone know why? $(function(){ $.extend( { _prepareYQLQuery: function (query, params) { $.each( params, function (key) { var name = "#{" + key + "}"; var value = $.trim(this); if (!value.match(/^[0-9]+$/)) { value = '"' + value + '"'; } query = query.replace(name, value); } ); return query; }, yql: function (query) { var $self = this; var successCallback = null; var errorCallback = null; if (typeof arguments[1] == 'object') { query = $self._prepareYQLQuery(query, arguments[1]); successCallback = arguments[2]; errorCallback = arguments[3]; } else if (typeof arguments[1] == 'function') { successCallback = arguments[1]; errorCallback = arguments[2]; } var doAsynchronously = successCallback != null; var yqlJson = { url: "http://query.yahooapis.com/v1/public/yql", dataType: "jsonp", success: successCallback, async: doAsynchronously, data: { q: query, format: "json", env: 'store://datatables.org/alltableswithkeys', callback: "?" } } if (errorCallback) { yqlJson.error = errorCallback; } $.ajax(yqlJson); return $self.toReturn; } } ); $.yql( "SELECT * FROM github.repo WHERE id='#{username}' AND repo='#{repository}'", { username: "jquery", repository: "jquery" }, function (data) { if (data.results.repository["open-issues"].content > 0) { alert("Hey dude, you should check out your new issues!"); } } ); });

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• NHibernate many-to-many relationship does not update join-table

  - by Davide Vosti

  I'm having trouble saving a many-to-many relationship with nhibernate. I searched and looked at almost every same question in SO and google but nothing works. The single classes are update correctly but nothing is inserted in the join-table. I have 2 classes: Event and Category. The mapping is this: Event: <bag name="Categories" access="field.camelcase-underscore" table="EventCategories" inverse="true" cascade="all-delete-orphan" lazy="true"> <key column="Event"/> <many-to-many class="Category" column="Category"/> </bag> Category: <bag name="Events" table="EventCategories" access="field.camelcase-underscore" cascade="all-delete-orphan" lazy="true" > <key column="Category"/> <many-to-many class="Event" column="Event"/> </bag> I tried to swap every parameter in both mappings but nothing works... Do you know what I'm doing wrong or have a right mapping for this case? Thank you very much!

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• copy child collection to another object

  - by Bogdan

  Hi everyone, I have a one-to-many relationship between Part and Params (a "Part" has many "Params). I'm trying to do something naive like this: Part sourcePart = em.find(Part.class, partIdSource); Part destPart = em.find(Part.class, partIdDest); Collection<Param> paramListSource = sourcePart.getParamList(); destPart.setParamList(paramListSource); Basically I want to copy all the parameters from sourcePart to destPart. Hopefully the persistence provider will automatically set the right foreign keys in the Param table/entity. The above code will obviously not work. Is there any easy way of doing this, or do I have to do create a new collection, then add each Param (creating new Param, setting attributes, etc) ?

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• mySQL & Relational databases: How to handle sharding/splitting on application level?

  - by Industrial

  Hi everybody, I have thought a bit about sharding tables, since partitioning cannot be done with foreign keys in a mySQL table. Maybe there's an option to switch to a different relational database that features both, but I don't see that as an option right now. So, the sharding idea seems like a pretty decent thing. But, what's a good approach to do this on a application level? I am guessing that a take-off point would be to prefix tables with a max value for the primary key in each table. Something like products_4000000 , products_8000000 and products_12000000. Then the application would have to check with a simple if-statement the size of the id (PK) that will be requested is smaller then four, eight or twelve million before doing any actual database calls. So, is this a step in the right direction or are we doing something really stupid?

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• Why does this ActionFilterAttribute not import data to the ViewModel?

  - by Tomas Lycken

  I have the following attribute public class ImportStatusAttribute : ActionFilterAttribute { public override void OnActionExecuted(ActionExecutedContext filterContext) { var model = (IHasStatus)filterContext.Controller.ViewData.Model; model.Status = (StatusMessageViewModel)filterContext.Controller.TempData["status"]; filterContext.Controller.ViewData.Model = model; } } which I test with the following test method (the first of several I'll write when this one passes...) [TestMethod] public void OnActionExecuted_ImportsStatusFromTempDataToModel() { // Arrange Expect(new { Status = new StatusMessageViewModel() { Subject = "The test", Predicate = "has been tested" }, Key = "status" }); var filterContext = new Mock<ActionExecutedContext>(); var model = new Mock<IHasStatus>(); var tempData = new TempDataDictionary(); var viewData = new ViewDataDictionary(model.Object); var controller = new FakeController() { ViewData = viewData, TempData = tempData }; tempData.Add(expected.Key, expected.Status); filterContext.Setup(c => c.Controller).Returns(controller); var attribute = new ImportStatusAttribute(); // Act attribute.OnActionExecuted(filterContext.Object); // Assert Assert.IsNotNull(model.Object.Status, "The status was not exported"); Assert.AreEqual(model.Object.Status.ToString(), ((StatusMessageViewModel)expected.Status).ToString(), "The status was not the expected"); } (Expect() is a method that saves some expectations in the expected object...) When I run the test, it fails on the first assertion, and I can't get my head around why. Debugging, I can see that model is populated correctly, and that (StatusMessageViewModel)filterContext.Controller.TempData["status"] has the correct data. But after model.Status = (StatusMessageViewModel)filterContext.Controller.TempData["status"]; model.Status is still null in my watch window. Why can't I do this?

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• Call to a member function get_segment() error

  - by hogofwar

  I'm having this problem with this piece of PHP code: class Core { public function start() { require("funk/funks/libraries/uri.php"); $this->uri = new uri(); require("funk/core/loader.php"); $this->load = new loader(); if($this->uri->get_segment(1) != "" and file_exists("funk/pages/".$uri->get_segment(1).".php")){ Only a snippet of the code The best way I can explain it is that it is a class calling upon another class (uri.php) and i am getting the error: Fatal error: Call to a member function get_segment() on a non-object in /home/eeeee/public_html/private/funkyphp/funk/core/core.php on line 11 (the if($this-uri-get_segment(1) part) I'm having this problem a lot and it is really bugging me. the library code is: <?php class uri { private $server_path_info = ''; private $segment = array(); private $segments = 0; public function __construct() { $segment_temp = array(); $this->server_path_info = preg_replace("/\?/", "", $_SERVER["PATH_INFO"]); $segment_temp = explode("/", $this->server_path_info); foreach ($segment_temp as $key => $seg) { if (!preg_match("/([a-zA-Z0-9\.\_\-]+)/", $seg) || empty($seg)) unset($segment_temp[$key]); } foreach ($segment_temp as $k => $value) { $this->segment[] = $value; } unset($segment_temp); $this->segments = count($this->segment); } public function segment_exists($id = 0) { $id = (int)$id; if (isset($this->segment[$id])) return true; else return false; } public function get_segment($id = 0) { $id--; $id = (int)$id; if ($this->segment_exists($id) === true) return $this->segment[$id]; else return false; } } ?>

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• Weird behavior of matching array keys after json_decode()

  - by arnorhs

  I've got some very weird behavior in my PHP code. I don't know if this is actually a good SO question, since it almost looks like a bug in PHP. I had this problem in a project of mine and isolated the problem: // json object that will be converted into an array $json = '{"5":"88"}'; $jsonvar = (array) json_decode($json); // notice: Casting to an array // Displaying the array: var_dump($jsonvar); // Testing if the key is there var_dump(isset($jsonvar["5"])); var_dump(isset($jsonvar[5])); That code outputs the following: array(1) { ["5"]=> string(2) "88" } bool(false) bool(false) The big problem: Both of those tests should produce bool(true) - if you create the same array using regular php arrays, this is what you'll see: // Let's create a similar PHP array in a regular manner: $phparr = array("5" => "88"); // Displaying the array: var_dump($phparr); // Testing if the key is there var_dump(isset($phparr["5"])); var_dump(isset($phparr[5])); The output of that: array(1) { [5]=> string(2) "88" } bool(true) bool(true) So this doesn't really make sense. I've tested this on two different installations of PHP/apache. You can copy-paste the code to a php file yourself to test it. It must have something to do with the casting from an object to an array.

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• django form ModelChoiceField loads all state names while needed states which are mapped with current selected country

  - by Sonu

  I am using modelChoiceField to display country and state into address form class StateSelectionwidget(forms.Select): """ custom widget to state selection""" class Media: js = ('media/javascript/public/jquery-1.5.2.min.js', 'media/javascript/public/countrystateselection.js', ) class AddressForm(forms.Form): name = forms.CharField(max_length=30) country = forms.ModelChoiceField(queryset=[]) state = forms.ModelChoiceField(CountryState.objects, widget=StateSelectionwidget) def __init__(self, *args, **kwargs): super(AddressForm, self).__init__(*args, **kwargs) self.fields['country'].queryset = Country.objects.all() Country model is used to store country names. CountryState model is used to store all states which is foreign key to Country model At the time of form loading i am getting all state names in dropdown while i want field to be blank by default. If name field is empty at the time of form save i am getting error that name can not be empty but also getting all states into dropdown list while i want only the states which are mapped with current selected country.

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• SQLAlchemy, one to many vs many to one

  - by sadvaw

  Dear Everyone, I have the following data: CREATE TABLE `groups` ( `bookID` INT NOT NULL, `groupID` INT NOT NULL, PRIMARY KEY(`bookID`), KEY( `groupID`) ); and a book table which basically has books( bookID, name, ... ), but WITHOUT groupID. There is no way for me to determine what the groupID is at the time of the insert for books. I want to do this in sqlalchemy. Hence I tried mapping Book to the books joined with groups on book.bookID=groups.bookID. I made the following: tb_groups = Table( 'groups', metadata, Column('bookID', Integer, ForeignKey('books.bookID'), primary_key=True ), Column('groupID', Integer), ) tb_books = Table( 'books', metadata, Column('bookID', Integer, primary_key=True), tb_joinedBookGroup = sql.join( tb_books, tb_groups, \ tb_books.c.bookID == tb_groups.c.bookID) and defined the following mapper: mapper( Group, tb_groups, properties={ 'books': relation(Book, backref='group') }) mapper( Book, tb_joinedBookGroup ) ... However, when I execute this piece of code, I realized that each book object has a field groups, which is a list, and each group object has books field which is a singular assigment. I think my definition here must have been causing sqlalchemy to be confused about the many-to-one vs one-to-many relationship. Can someone help me sort this out? My desired goal is g.books = [b, b, b, .. ] book.group = g, where g is an instance of group, and b is an instance of book

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• FluentNHibernate: Not.Nullable() doesn't affect output schema

  - by alex

  Hello I'm using fluent nhibernate v. 1.0.0.595. There is a class: public class Weight { public virtual int Id { get; set; } public virtual double Value { get; set; } } I want to map it on the following table: create table [Weight] ( WeightId INT IDENTITY NOT NULL, Weight DOUBLE not null, primary key (WeightId) ) Here is the map: public class WeightMap : ClassMap<Weight> { public WeightMap() { Table("[Weight]"); Id(x => x.Id, "WeightId"); Map(x => x.Value, "Weight").Not.Nullable(); } } The problem is that this mapping produces table with nullable Weight column: Weight DOUBLE null Not-nullable column is generated only with default convention for column name (i.e. Map(x = x.Value).Not.Nullable() instead of Map(x = x.Value, "Weight").Not.Nullable()), but in this case there will be Value column instead of Weight: create table [Weight] ( WeightId INT IDENTITY NOT NULL, Value DOUBLE not null, primary key (WeightId) ) I found similiar problem here: http://code.google.com/p/fluent-nhibernate/issues/detail?id=121, but seems like mentioned workaround with SetAttributeOnColumnElement("not-null", "true") is outdated. Does anybody encountered with this problem? Is there a way to specify named column as not-nullable?

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• django forms from two tables referencial integrity

  - by dana

  i have a class named cv,and a class named university, and each user that completes his cv, should choose a University he studyes at. My problem is: one student can study at one or 2 or three universities, or may be a user that is not student. I need to take this data into a form, and i use ModelForm. The data from the Cv class, and from the University class in the same form, and the user can add one or more universities, or no university. (in the same form) How should i do it? Should i use ModelForm? if i have a foreign key in the CV class, and the user is not a student (so he is at zero universities), i may get an referencial integrity error. thanks a lot

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