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  • Movement prediction for non-shooters

    - by ShadowChaser
    I'm working on an isometric (2D) game with moderate-scale multiplayer - 20-30 players. I've had some difficulty getting a good movement prediction implementation in place. Right now, clients are authoritative for their own position. The server performs validation and broad-scale cheat detection, and I fully realize that the system will never be fully robust against cheating. However, the performance and implementation tradeoffs work well for me right now. Given that I'm dealing with sprite graphics, the game has 8 defined directions rather than free movement. Whenever the player changes their direction or speed (walk, run, stop), a "true" 3D velocity is set on the entity and a packet it sent to the server with the new movement state. In addition, every 250ms additional packets are transmitted with the player's current position for state updates on the server as well as for client prediction. After the server validates the packet, it gets automatically distributed to all of the other "nearby" players. Client-side, all entities with non-zero velocity (ie/ moving entities) are tracked and updated by a rudimentary "physics" system - basically nothing more than changing the position by the velocity according to the elapsed time slice (40ms or so). What I'm struggling with is how to implement clean movement prediction. I have the nagging suspicion that I've made a design mistake somewhere. I've been over the Unreal, Half-life, and all other movement prediction/lag compensation articles I could find, but they all seam geared toward shooters: "Don't send each control change, send updates every 120ms, server is authoritative, client predicts, etc". Unfortunately, that style of design won't work well for me - there's no 3D environment so each individual state change is important. 1) Most of the samples I saw tightly couple movement prediction right into the entities themselves. For example, storing the previous state along with the current state. I'd like to avoid that and keep entities with their "current state" only. Is there a better way to handle this? 2) What should happen when the player stops? I can't interpolate to the correct position, since they might need to walk backwards or another strange direction if their position is too far ahead. 3) What should happen when entities collide? If the current player collides with something, the answer is simple - just stop the player from moving. But what happens if two entities take up the same space on the server? What if the local prediction causes a remote entity to collide with the player or another entity - do I stop them as well? If the prediction had the misfortune of sticking them in front of a wall that the player has gone around, the prediction will never be able to compensate and once the error gets to high the entity will snap to the new position.

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  • How to avoid Windows Genuine Advantage for an XP update?

    - by hlovdal
    I am about to apply updates to a windows xp installation I have not booted in a couple of years. When going to update.microsoft.com, it forced me first to accept an activex installation and now it wants me to install wga: Windows Update To use this latest version of Windows Update, you will need to upgrade some of its components. This version provides you with the following enhancements to our service: <... useless list of "advantages" ... Details Windows Genuine Advantage Validation Tool (KB892130) 1.1 MB , less than 1 minute The Windows Genuine Advantage Validation Tool enables you to verify that your copy of Microsoft Windows is genuine. The tool validates your Windows installation by checking Windows Product Identification and Product Activation status. Update for Windows XP (KB898461) 477 KB , less than 1 minute This update installs a permanent copy of Package Installer for Windows to enable software updates to have a significantly smaller download size. The Package Installer facilitates the install of software updates for Microsoft Windows operating systems and other Microsoft products. After you install this update, you may have to restart your system. Total: 1.5 MB , less than 1 minute I have heard nothing but bad things about wga, and I absolutely do not want it installed on my system (this answer seems to give some options). Searching for "windows xp" at microsoft's web pages brought up this page which says Windows XP Service Pack 3 Network Installation Package for IT Professionals and Developers Brief Description This installation package is intended for IT professionals and developers downloading and installing on multiple computers on a network. If you're updating just one computer, please visit Windows Update at http://update.microsoft.com . ... File Name: WindowsXP-KB936929-SP3-x86-ENU.exe I am currently downloading this file. Will installing this bring my installation up to date with security updates? What about later updates whenever a new problem is discovered, how can i update without using wga?

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  • OARC's DNSSEC validating resolvers validate all my records but A records

    - by demize
    I have DNS set up with powerdns. It serves my DNS pretty well, and it AXFRs to other slaves. The slaves haven't yet updated to the most recent records, but that doesn't affect the validation, it would appear. Any record I can think of (AAAA, MX, TXT, even the CNAME for www) validates -- except for A records: dig @149.20.64.20 +dnssec www.demize95.com CNAME returns ;; flags: qr rd ra ad; QUERY: 1, ANSWER: 2, AUTHORITY: 5, ADDITIONAL: 7 while dig @149.20.64.20 +dnssec demize95.com A returns ;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 5, ADDITIONAL: 7. The same happens with any other A record I have. I set up DNSSEC with pdnssec, and it does work for all the other records, but it's never validated for my A records. What's the problem here? Also, a side-note: I have to use ISC's DLV to create the chain of trust, since my domain registrar doesn't yet support sending the DS records to the com zone.

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  • Free blog sites where the blogs can (if the template does) validate as XHTML Strict 1.0?

    - by Deleted
    I'm looking for a site where I may register a free blog and have the blog validate as XHTML Strict 1.0. On the surface this may seem like a trivial problem only related to the theme/template in use, but that's unfortunately not the case. One example of a provider which can't fullfill this requirement is Blogger. Altough the pages of the blogs there presents themselfs as XHTML 1.0 Strict it is impossible to actually comply with the requirements inheritied by that markup type in the blog (as the XHTML which is generated by Blogger makes the page as a whole invalid). I've sent a mail to Tumblr to see if it was possible with them, but so far my reply consists of them having forwarded my mail with a "suggestion" to the development department. I don't know if we had a communication error or if I'm actually going to receive a proper answer later. Time will tell. I haven't had time to investigate Tumblr myself, so they may very well be the solution to this problem. To sum things up, I'm looking for any provider: Of a free blog. The blog must have the capability to validate as XHTML Strict 1.0. With capability I mean that the system shouldn't get in the way of creating/using a theme which complies as XHTML Strict 1.0. Preferably is large or at least likely to stay around for a couple of years to come. But I'm willing to take my chances if none of the established providers are up to the task. Thank you for reading! I hope you know of any provider which would be suitable, preferably with proof by linking to a blog there which validates. I'm not looking for suggestions to look into, as there are far to many to investigate and far too little time. If you know of something for sure, I'd be very happy to know about it.

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  • Postfix: How to configure Postfix with virtual Dovecot mailboxes?

    - by user75247
    I have configured a Postfix mail server for two domains: domain1.com and domain2.com. In my configuration domain1 has both virtual users with Maildirs and aliases to forward mail to local users (eg. root, webmaster) and some small mailing lists. It also has some virtual mappings to non-local domains. Domain2 on the other hand has only virtual alias mappings, mainly to corresponding 'users' at domain1 (eg. mails to [email protected] should be forwarded to [email protected]). My problem is that currently Postfix accepts mail even for those users that don't exist in the system. Mail to existing users and /etc/aliases works fine. Postfix documentation states that the same domain should never be specified in both mydestination and virtual_mailbox_maps, but If I specify mydestination as blank then postfix validates recipients against virtual_mailbox_maps but rejects mail for local aliases of domain1.com. /etc/postfix/main.cf: myhostname = domain1.com mydomain = domain1.com mydestinations = $myhostname, localhost.$mydomain, localhost virtual_mailbox_domains = domain1.com virtual_mailbox_maps = hash:/etc/postfix/vmailbox virtual_mailbox_base = /home/vmail/domains virtual_alias_domains = domain2.com virtual_alias_maps = hash:/etc/postfix/virtual alias_maps = hash:/etc/aliases alias_database = hash:/etc/aliases virtual_transport = dovecot /etc/postfix/virtual: domain1.com right-hand-content-does-not-matter firstname.lastname user1 [more aliases..] domain2.com right-hand-content-does-not-matter @domain2.com @domain1.com /etc/postfix/vmailbox: [email protected] user1/Maildir [email protected] user2/Maildir /etc/aliases: root: :include:/etc/postfix/aliases/root webmaster: :include:/etc/postfix/aliases/webmaster [etc..] Is this approach correct or is there some other way to configure Postfix with Dovecot (virtual) Maildirs and Postfix aliases?

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  • Need to set up a proxy on Linksys E3200 to filter home internet

    - by Justin Amberson
    the fact that I have a Linksys E3200 may not be important. I can configure the router through the web interface, but I don't know the things I will be toggling are called. I already do simple port forwarding to access applications on my Mac remotely. So router admin is not something I technically need explained. I'm looking to running a proxy on my home computer, that filters all HTTP traffic that goes through my router. So if my daughter is on her iPad and accesses Safari, my Mac will be the judge of the validity of the request. I need something like NetNanny I guess, but local. Actually, anything that can just filter all port 80 traffic that runs locally, but maybe validates with a password? I truly truly hope this question falls within the bounds of Serverfault. I'm not a total internet newb but I'm at a loss for what to Google. If possible answer this question: Is there a webapp that can listen on port 80, and validate requests to port 80 with a password? If so, can I forward all traffic on port 80 to my Mac, to be re-routed to the user? Is this the same as a VPN? Thank you for your help. Justin

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  • Avoid Jquery Plugin Conflict

    - by user1511579
    on the same page i'm using this plugin: $g=jQuery.noConflict(); $g(function() { /* number of fieldsets */ var fieldsetCount = $g('#formElem').children().length; /* current position of fieldset / navigation link */ var current = 1; /* sum and save the widths of each one of the fieldsets set the final sum as the total width of the steps element */ var stepsWidth = 0; var widths = new Array(); $g('#steps .step').each(function(i){ var $step = $g(this); widths[i]   = stepsWidth; stepsWidth += $step.width(); }); $g('#steps').width(stepsWidth); /* to avoid problems in IE, focus the first input of the form */ $g('#formElem').children(':first').find(':input:first').focus(); /* show the navigation bar */ $g('#navigation_form').show(); /* when clicking on a navigation link  the form slides to the corresponding fieldset */ $g('#navigation_form a').bind('click',function(e){ var $this = $g(this); var prev = current; $this.closest('ul').find('li').removeClass('selected'); $this.parent().addClass('selected'); /* we store the position of the link in the current variable */ current = $this.parent().index() + 1; /* animate / slide to the next or to the corresponding fieldset. The order of the links in the navigation is the order of the fieldsets. Also, after sliding, we trigger the focus on the first  input element of the new fieldset If we clicked on the last link (confirmation), then we validate all the fieldsets, otherwise we validate the previous one before the form slided */ $g('#steps').stop().animate({ marginLeft: '-' + widths[current-1] + 'px' },500,function(){ if(current == fieldsetCount) validateSteps(); else validateStep(prev); $g('#formElem').children(':nth-child('+ parseInt(current) +')').find(':input:first').focus(); }); e.preventDefault(); }); /* clicking on the tab (on the last input of each fieldset), makes the form slide to the next step */ $g('#formElem > fieldset').each(function(){ var $fieldset = $g(this); $fieldset.children(':last').find(':input').keydown(function(e){ if (e.which == 9){ $g('#navigation_form li:nth-child(' + (parseInt(current)+1) + ') a').click(); /* force the blur for validation */ $g(this).blur(); e.preventDefault(); } }); }); /* validates errors on all the fieldsets records if the Form has errors in $('#formElem').data() */ function validateSteps(){ var FormErrors = false; for(var i = 1; i < fieldsetCount; ++i){ var error = validateStep(i); if(error == -1) FormErrors = true; } $g('#formElem').data('errors',FormErrors); } /* validates one fieldset and returns -1 if errors found, or 1 if not */ function validateStep(step){ if(step == fieldsetCount) return; var error = 1; var hasError = false; $g('#formElem').children(':nth-child('+ parseInt(step) +')').find(':input:not(button)').each(function(){ var $this = $g(this); var valueLength = jQuery.trim($this.val()).length; if(valueLength == ''){ hasError = true; $this.css('background-color','#FFEDEF'); } else $this.css('background-color','#FFFFFF'); }); var $link = $g('#navigation_form li:nth-child(' + parseInt(step) + ') a'); $link.parent().find('.error,.checked').remove(); var valclass = 'checked'; if(hasError){ error = -1; valclass = 'error'; } $g('<span class="'+valclass+'"></span>').insertAfter($link); return error; } /* if there are errors don't allow the user to submit */ $g('#registerButton').bind('click',function(){ if($g('#formElem').data('errors')){ alert('Please correct the errors in the Form'); return false; } }); }); and this one: (function($){ $countCursos = 1; $countFormsA = 1; $countFormsB = 1; $.fn.addForms = function(idform){ var adicionar_curso = "<p>"+ " <label for='nome_curso'>Nome do Curso</label>"+ " <input id='nome_curso' name='nome_curso["+$countCursos+"]' type='text' />"+ " </p>"; var myform2 = "<table>"+ " <tr>"+ " <td>Field C</td>"+ " <td><input type='text' name='fieldc["+$countFormsA+"]'></td>"+ " <td>Field D ("+$countFormsA+"):</td>"+ " <td><textarea name='fieldd["+$countFormsA+"]'></textarea></td>"+ " <td><button>remove</button></td>"+ " </tr>"+ "</table>"; var myform3 = "<table>"+ " <tr>"+ " <td>Field C</td>"+ " <td><input type='text' name='fieldc["+$countFormsB+"]'></td>"+ " <td>Field D ("+$countFormsB+"):</td>"+ " <td><textarea name='fieldd["+$countFormsB+"]'></textarea></td>"+ " <td><button>remove</button></td>"+ " </tr>"+ "</table>"; if(idform=='novo_curso'){ alert(idform); adicionar_curso = $("<div>"+adicionar_curso+"</div>"); $("button", $(adicionar_curso)).click(function(){ $(this).parent().parent().remove(); }); $(this).append(adicionar_curso); $countCursos++; } if(idform=='mybutton1'){ alert(idform); myform2 = $("<div>"+myform2+"</div>"); $("button", $(myform2)).click(function(){ $(this).parent().parent().remove(); }); $(this).append(myform2); $countFormsA++; } if(idform=='mybutton2'){ alert(idform); myform3 = $("<div>"+myform3+"</div>"); $("button", $(myform3)).click(function(){ $(this).parent().parent().remove(); }); $(this).append(myform3); $countFormsB++; } }; })(jQuery); $(function(){ $("#mybutton1").bind("click", function(e){ e.preventDefault(); var idform=this.id; if($countFormsA<3){ $("#container1").addForms(idform); } }); }); $(function(){ $("#novo_curso").bind("click", function(e){ e.preventDefault(); var idform=this.id; alert(idform); if($countCursos<3){ $("#outro_curso").addForms(idform); } }); }); $(function(){ $("#mybutton2").bind("click", function(e){ e.preventDefault(); var idform=this.id; if($countFormsB<3){ $("#container2").addForms(idform); } }); }); My problem is the two are making conflict: I added previously the $g on the first to avoid conflict, but the truth is they don't work together, any hint how can i configure the second one to avoid this? Thanks in advance!

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  • forEach and Facelets - a bugfarm just waiting for harvest

    - by Duncan Mills
    An issue that I've encountered before and saw again today seems worthy of a little write-up. It's all to do with a subtle yet highly important difference in behaviour between JSF 2 running with JSP and running on Facelets (.jsf pages). The incident I saw today can be seen as a report on the ADF EMG bugzilla (Issue 53) and in a blog posting by Ulrich Gerkmann-Bartels who reported the issue to the EMG. Ulrich's issue nicely shows how tricky this particular gochya can be. On the surface, the problem is squarely the fault of MDS but underneath MDS is, in fact, innocent. To summarize the problem in a simpler testcase than Ulrich's example, here's a simple fragment of code: <af:forEach var="item" items="#{itemList.items}"> <af:commandLink id="cl1" text="#{item.label}" action="#{item.doAction}"  partialSubmit="true"/> </af:forEach> Looks innocent enough right? We see a bunch of links printed out, great. The issue here though is the id attribute. Logically you can kind of see the problem. The forEach loop is creating (presumably) multiple instances of the commandLink, but only one id is specified - cl1. We know that IDs have to be unique within a JSF component tree, so that must be a bad thing?  The problem is that JSF under JSP implements some hacks when the component tree is generated to transparently fix this problem for you. Behind the scenes it ensures that each instance really does have a unique id. Really nice of it to do so, thank you very much. However, (you could see this coming), the same is not true when running with Facelets  (this is under 11.1.2.n)  in that case, what you put for the id is what you get, and JSF does not mess around in the background for you. So you end up with a component tree that contains duplicate ids which are only created at runtime.  So subtle chaos can ensue.  The symptoms are wide and varied, from something pretty obscure such as the combination Ulrich uncovered, to something as frustrating as your ActionListener just not being triggered. And yes I've wasted hours on just such an issue.  The Solution  Once you're aware of this one it's really simple to fix it, there are two options: Remove the id attribute on components that will cause some kind of submission within the forEach loop altogether and let JSF do the right thing in generating them. Then you'll be assured of uniqueness. Use the var attribute of the loop to generate a unique id for each child instance.  for example in the above case: <af:commandLink id="cl1_#{item.index}" ... />.  So one to watch out for in your upgrades to JSF 2 and one perhaps, for your coding standards today to prepare you for. For completeness, here's the reference to the underlying JSF issue that's at the heart of this: JAVASERVERFACES-1527

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  • Silverlight and Encryption, how to store/generate they key/iv pair?

    - by cmaduro
    I have a Silverlight app that connects to a php webservice. I want to encrypt the communication between the webservice and the Silverlight client. I'm not relying on SSL. I'm encrypting/decrypting the POST string myself using AES 256bit Key and IV. The big questions then are: How do I generate a random unique key/iv pair in PHP. How do I share this key/iv pair between the web service and silverlight client in a secure way. It seems impossible without having some kind of hard coded key or iv on the client. Which would compromise security. This is a public website, there are no logins. Just the requirement of secure communication. I can hard code the seed for the key/iv (which is hashed with SHA256 with a time stamp salt and then assigned as the key or iv) in PHP source code, that's on the server so that is pretty safe. However on the client the seed for the key/iv pair would be visible, if it is hard coded. Further more using a time stamp as the basis for uniqueness/randomness is definitely not ok, since timestamps are predictable. It does however provide a common factor between the C# code and the PHP code. The only other option that I can think of would be to have a 3rd service involved that provides the key/iv to the Silverlight client, as well as the php webservice. This of course start the cycle anew, with the question of how to store the credentials for accessing the key/iv distribution service on the Silverlight client. Sounds like the solution is then asymmetric encryption, since sensitive data will be viewed only on the administrative back end of the website. Unfortunately Silverlight has no asymmetric encryption classes. The solution? Roll my own Diffie-Hellman key exchange! Plug that key into AES256!

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  • Question about SQL Server HierarchyID depth-first performance

    - by AndalusianCat
    I am trying to implement hierarchyID in a table (dbo.[Message]) containing roughly 50,000 rows (will grow substantially in the future). However it takes 30-40 seconds to retrieve about 25 results. The root node is a filler in order to provide uniqueness, therefor every subsequent row is a child of that dummy row. I need to be able to traverse the table depth-first and have made the hierarchyID column (dbo.[Message].MessageID) the clustering primary key, have also added a computed smallint (dbo.[Message].Hierarchy) which stores the level of the node. Usage: A .Net application passes through a hierarchyID value into the database and I want to be able to retrieve all (if any) children AND parents of that node (besides the root, as it is filler). A simplified version of the query I am using: @MessageID hierarchyID /* passed in from application */ SELECT m.MessageID, m.MessageComment FROM dbo.[Message] as m WHERE m.Messageid.IsDescendantOf(@MessageID.GetAncestor((@MessageID.GetLevel()-1))) = 1 ORDER BY m.MessageID From what I understand, the index should be detected automatically without a hint. From searching forums I have seen people utilizing index hints, at least in the case of breadth-first indexes, as apparently CLR calls may be opaque to the query optimizer. I have spent the past few days trying to find a solution for this issue, but to no avail. I would greatly appreciate any assistance, and as this is my first post, I apologize in advance if this would be considered a 'noobish' question, I have read the MS documentation and searched countless forums, but have not came across a succinct description of the specific issue.

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  • Building simple Reddit scraper

    - by Bazant Fundator
    Let's say that I would like to make a collection of images from reddit for my own amusement. I have ran the code on my development env and It haven't gone past the first page of posts (anything beyond requries the after string from the JSON. Additionally, When I turn on the validation, the whole loop breaks if the item doesn't pass it, not just the current iteration. I would be glad If you helped me understand mistakes I made. class Link include Mongoid::Document include Mongoid::Timestamps field :author, type: String field :url, type: String validates_uniqueness_of :url, # no duplicates validates :url, uniqueness :true end def fetch (count, after) count_s = count.to_s # convert count to string link = "http://reddit.com/r/aww/.json?count="+count_s+"&after="+after #so it can be used there res = HTTParty.get(link) # GET req. to the reddit server json = JSON.parse(res.body) # Parse the response if json['kind'] == "Listing" then # check if the retrieved item is a Listing for i in 1...(count) do # for each list item datum = json['data']['children'][i]['data'] #i-th element properties if datum['domain'].in?(["imgur.com", "i.imgur.com"]) then # fetch only imgur links Link.create!(author: datum['author'], url: datum['url']) # save to db end end count += 25 fetch(count, json['data']['after']) # if it retrieved the right kind of object, move on to the next page end end fetch(25," ") # run it

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  • Hibernate : Opinions in Composite PK vs Surrogate PK

    - by Albert Kam
    As i understand it, whenever i use @Id and @GeneratedValue on a Long field inside JPA/Hibernate entity, i'm actually using a surrogate key, and i think this is a very nice way to define a primary key considering my not-so-good experiences in using composite primary keys, where : there are more than 1 business-value-columns combination that become a unique PK the composite pk values get duplicated across the table details cannot change the business value inside that composite PK I know hibernate can support both types of PK, but im left wondering by my previous chats with experienced colleagues where they said that composite PK is easier to deal with when doing complex SQL queries and stored procedure processes. They went on saying that when using surrogate keys will complicate things when doing joining and there are several condition when it's impossible to do some stuffs when using surrogate keys. Although im sorry i cant explain the detail here since i was not clear enough when they explain it. Maybe i'll put more details next time. Im currently trying to do a project, and want to try out surrogate keys, since it's not getting duplicated across tables, and we can change the business-column values. And when the need for some business value combination uniqueness, i can use something like : @Table(name="MY_TABLE", uniqueConstraints={ @UniqueConstraint(columnNames={"FIRST_NAME", "LAST_NAME"}) // name + lastName combination must be unique But im still in doubt because of the previous discussion about the composite key. Could you share your experiences in this matter ? Thank you !

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  • SQL Server 2005, wide indexes, computed columns, and sargable queries

    - by luksan
    In my database, assume we have a table defined as follows: CREATE TABLE [Chemical]( [ChemicalId] int NOT NULL IDENTITY(1,1) PRIMARY KEY, [Name] nvarchar(max) NOT NULL, [Description] nvarchar(max) NULL ) The value for Name can be very large, so we must use nvarchar(max). Unfortunately, we want to create an index on this column, but nvarchar(max) is not supported inside an index. So we create the following computed column and associated index based upon it: ALTER TABLE [Chemical] ADD [Name_Indexable] AS LEFT([Name], 20) CREATE INDEX [IX_Name] ON [Chemical]([Name_Indexable]) INCLUDE([Name]) The index will not be unique but we can enforce uniqueness via a trigger. If we perform the following query, the execution plan results in a index scan, which is not what we want: SELECT [ChemicalId], [Name], [Description] FROM [Chemical] WHERE [Name]='[1,1''-Bicyclohexyl]-2-carboxylic acid, 4'',5-dihydroxy-2'',3-dimethyl-5'',6-bis[(1-oxo-2-propen-1-yl)oxy]-, methyl ester' However, if we modify the query to make it "sargable," then the execution plan results in an index seek, which is what we want: SELECT [ChemicalId], [Name], [Description] FROM [Chemical] WHERE [Indexable_Name]='[1,1''-Bicyclohexyl]-' AND [Name]='[1,1''-Bicyclohexyl]-2-carboxylic acid, 4'',5-dihydroxy-2'',3-dimethyl-5'',6-bis[(1-oxo-2-propen-1-yl)oxy]-, methyl ester' Is this a good solution if we control the format of all queries executed against the database via our middle tier? Is there a better way? Is this a major kludge? Should we be using full-text indexing?

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  • Using MongoDB's map/reduce to "group by" two fields

    - by ibz
    I need something slightly more complex than the examples in the MongoDB docs and I can't seem to be able to wrap my head around it. Say I have a collection of objects of the form {date: "2010-10-10", type: "EVENT_TYPE_1", user_id: 123, ...} Now I want to get something similar to a SQL GROUP BY query, grouping over both date and type. That is, I want the number of events of each type in each day. Also, I'd like to make it unique by user_id, ie. if a user has more events in the same day, count it only once. I'm trying to do this with map/reduce. I do db.logs.mapReduce(function() { emit(this.type, 1); }, function(k, vals) { var total = 0; for (var i = 0; i < vals.length; i++) total += vals[i]; return total; }}) which nicely groups by type, but now, how can I group by date at the same time? Seems the key in emit() can't be an array (I thought about doing emit([this.date, this.type], 1)). Also, how can I ensure the per-user uniqueness? I'm just starting with MongoDB and I'm still having trouble grasping the basic concepts. Also, there is not much documentation available out there. Any help from more experienced users is appreciated. Thanks!

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  • How to represent and insert into an ordered list in SQL?

    - by Travis
    I want to represent the list "hi", "hello", "goodbye", "good day", "howdy" (with that order), in a SQL table: pk | i | val ------------ 1 | 0 | hi 0 | 2 | hello 2 | 3 | goodbye 3 | 4 | good day 5 | 6 | howdy 'pk' is the primary key column. Disregard its values. 'i' is the "index" that defines that order of the values in the 'val' column. It is only used to establish the order and the values are otherwise unimportant. The problem I'm having is with inserting values into the list while maintaining the order. For example, if I want to insert "hey" and I want it to appear between "hello" and "goodbye", then I have to shift the 'i' values of "goodbye" and "good day" (but preferably not "howdy") to make room for the new entry. So, is there a standard SQL pattern to do the shift operation, but only shift the elements that are necessary? (Note that a simple "UPDATE table SET i=i+1 WHERE i=3" doesn't work, because it violates the uniqueness constraint on 'i', and also it updates the "howdy" row unnecessarily.) Or, is there a better way to represent the ordered list? I suppose you could make 'i' a floating point value and choose values between, but then you have to have a separate rebalancing operation when no such value exists. Or, is there some standard algorithm for generating string values between arbitrary other strings, if I were to make 'i' a varchar? Or should I just represent it as a linked list? I was avoiding that because I'd like to also be able to do a SELECT .. ORDER BY to get all the elements in order.

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  • multiple ajax requests with jquery

    - by Emil
    I got problems with the async nature of Javascript / JQuery. Lets say the following (no latency is counted for, in order to not make it so troublesome); I got three buttons (A, B, C) on a page, each of the buttons adds an item into a shopping cart with one ajax-request each. If I put an intentional delay of 5 seconds in the serverside script (PHP) and pushes the buttons with 1 second apart, I want the result to be the following: Request A, 5 seconds Request B, 6 seconds Request C, 7 seconds However, the result is like this Request A, 5 seconds Request B, 10 seconds Request C, 15 seconds This have to mean that the requests are queued and not run simultaneously, right? Isnt this opposite to what async is? I also tried to add a random get-parameter to the url in order to force some uniqueness to the request, no luck though. I did read a little about this. If you avoid using the same "request object (?)" this problem wont occure. Is it possible to force this behaviour in JQuery? This is the code that I am using $.ajax( { url : strAjaxUrl + '?random=' + Math.floor(Math.random()*9999999999), data : 'ajax=add-to-cart&product=' + product, type : 'GET', success : function(responseData) { // update ui }, error : function(responseData) { // show error } }); I also tried both GET and POST, no difference. I want the requests to be sent right when the button is clicked, not when the previous request is finnished. I want the requests to be run simultaneously, not in a queue.

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  • Improve Log Exceptions

    - by Jaider
    I am planning to use log4net in a new web project. In my experience, I see how big the log table can get, also I notice that errors or exceptions are repeated. For instance, I just query a log table that have more than 132.000 records, and I using distinct and found that only 2.500 records are unique (~2%), the others (~98%) are just duplicates. so, I came up with this idea to improve logging. Having a couple of new columns: counter and updated_dt, that are updated every time try to insert same record. If want to track the user that cause the exception, need to create a user_log or log_user table, to map N-N relationship. Create this model may made the system slow and inefficient trying to compare all these long text... Here the trick, we should also has a hash column of binary of 16 or 32, that hash the message and the exception, and configure an index on it. We can use HASHBYTES to help us. I am not an expert in DB, but I think that will made the faster way to locate a similar record. And because hashing doesn't guarantee uniqueness, will help to locale those similar record much faster and later compare by message or exception directly to make sure that are unique. This is a theoretical/practical solution, but will it work or bring more complexity? what aspects I am leaving out or what other considerations need to have? the trigger will do the job of insert or update, but is the trigger the best way to do it?

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  • Excess errors on model from somewhere

    - by gmile
    I have a User model, and use an acts_as_authentic (from authlogic) on it. My User model have 3 validations on username and looks as following: User < ActiveRecord::Base acts_as_authentic validates_presence_of :username validates_length_of :username, :within => 4..40 validates_uniqueness_of :username end I'm writing a test to see my validations in action. Somehow, I get 2 errors instead of one when validating a uniqueness of a name. To see excess error, I do the following test: describe User do before(:each) do @user = Factory.build(:user) end it "should have a username longer then 3 symbols" do @user2 = Factory(:user) @user.username = @user2.username @user.save puts @user.errors.inspect end end I got 2 errors on username: @errors={"username"=>["has already been taken", "has already been taken"]}. Somehow the validation passes two times. I think authlogic causes that, but I don't have a clue on how to avoid that. Another case of problem is when I set username to nil. Somehow I get four validation errors instead of three: @errors={"username"=>["is too short (minimum is 3 characters)", "should use only letters, numbers, spaces, and .-_@ please.", "can't be blank", "is too short (minimum is 4 characters)"]} I think authlogic is one that causes this strange behaviour. But I can't even imagine on how to solve that. Any ideas?

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  • A GUID as the MySQL table's Primary Key or as a separate column

    - by Ben
    I have a multi-process program that performs, in a 2 hour period, 5-10 million inserts to a 34GB table within a single Master/Slave MySQL setup (plus an equal number of reads in that period). The table in question has only 5 fields and 3 (single field) indexes. The primary key is auto-incrementing. I am far from a DBA, but the database appears to be crippled during this two hour period. So, I have a couple of general questions. 1) How much bang will I get out of batching these writes into units of 10? Currently, I am writing each insert serially because, after writing, I immediately need to know, in my program, the resulting primary key of each insert. The PK is the only unique field presently and approximating the order of insertion with something like a Datetime field or a multi-column value is not acceptable. If I perform a bulk insert, I won't know these IDs, which is a problem. So, I've been thinking about turning the auto-increment primary key into a GUID and enforcing uniqueness. I've also been kicking around the idea of creating a new column just for the purposes of the GUID. I don't really see the what that achieves though, that the PK approach doesn't already offer. As far as I can tell, the big downside to making the PK a randomly generated number is that the index would take a long time to update on each insert (since insertion order would not be sequential). Is that an acceptable approach for a table that is taking this number of writes? Thanks, Ben

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  • Adding li element only if it not already there?

    - by Legend
    I am constructing an <li> element like this: var element = $("<li></li>") .html(mHTML) .attr('id', "elemid"); I am trying to add this element to a <ul> element only if it doesn't already exist. Any ideas on how to do this? Am I supposed to use contains() to see if the ul element contain the html and then decide? For instance, <ul id="elemul"> <li id="elemli1">Element 1</li> <li id="elemli2">Element 2</li> <li id="elemli3">Element 3</li> </ul> If I try adding Element 1, it should not add it. What should I do if its a longer string (not really long but about 150 characters). Note: I cannot rely on IDs to determine the uniqueness. i.e. I might end up forming something like: <li id="elemli3">Element 1</li> Do I go about using hashmaps?

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  • Insert or Update using Oracle and PL/SQL

    - by Shane
    I have a PL/SQL function that performs an update/insert on an Oracle database that maintains a target total and returns the difference between the existing value and the new value. Here is the code I have so far: FUNCTION calcTargetTotal(accountId varchar2, newTotal numeric ) RETURN number is oldTotal numeric(20,6); difference numeric(20,6); begin difference := 0; begin select value into oldTotal from target_total WHERE account_id = accountId for update of value; if (oldTotal != newTotal) then update target_total set value = newTotal WHERE account_id = accountId difference := newTotal - oldTotal; end if; exception when NO_DATA_FOUND then begin difference := newTotal; insert into target_total ( account_id, value ) values ( accountId, newTotal ); -- sometimes a race condition occurs and this stmt fails -- in those cases try to update again exception when DUP_VAL_ON_INDEX then begin difference := 0; select value into oldTotal from target_total WHERE account_id = accountId for update of value; if (oldTotal != newTotal) then update target_total set value = newTotal WHERE account_id = accountId difference := newTotal - oldTotal; end if; end; end; end; return difference end calcTargetTotal; This works as expected in unit tests with multiple threads never failing. However when loaded on a live system we have seen this fail with a stack trace looking like this: ORA-01403: no data found ORA-00001: unique constraint () violated ORA-01403: no data found The line numbers (which I have removed since they are meaningless out of context) verify that the first update fails due to no data, the insert fail due to uniqueness, and the 2nd update is failing with no data, which should be impossible. From what I have read on other thread a MERGE statement is also not atomic and could suffer similar problems. Does anyone have any ideas how to prevent this from occurring?

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  • Random Alpha numeric generator

    - by AAA
    Hi, I want to give our users in the database a unique alpha-numeric id. I am using the code below, will this always generate a unique id? Below is the old and updated version of the code: New php: // Generate Guid function NewGuid() { $s = strtoupper(md5(uniqid("something",true))); $guidText = substr($s,0,8) . '-' . substr($s,8,4) . '-' . substr($s,12,4). '-' . substr($s,16,4). '-' . substr($s,20); return $guidText; } // End Generate Guid $Guid = NewGuid(); echo $Guid; echo "<br><br><br>"; Old PHP: // Generate Guid function NewGuid() { $s = strtoupper(md5(uniqid("something",true))); $guidText = substr($s,0,8) . '-' . substr($s,8,4) . '-' . substr($s,12,4). '-' . substr($s,16,4). '-' . substr($s,20); return $guidText; } // End Generate Guid $Guid = NewGuid(); echo $Guid; echo "<br><br><br>"; Will this first code guarantee uniqueness?

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  • In Rails, how to respect :scope when using validates_uniqueness_of in an embedded object form?

    - by mkirk
    I have a Book model, which has_many Chapters (which belong_to a Book). I want to ensure uniqueness of Chapter titles, but only within the scope of a single book. The catch is that the form for creating chapters is embedded in the Book model's form (The Book model accepts_nested_attributes_for :chapters). Within the Chapter model: validates_uniqueness_of( :chapter_title, :scope = :book_id, :case_sensitive = false, :message = "No book can have multiple chapters with the same title.") However, when I submit the Book creation form (which also includes multiple embedded Chapter forms), if the chapter title exists in another chapter for a different book, I fail the validation test. Book.create( :chapters => [ Chapter.new(:title => "Introduction"), Chapter.new(:title => "How to build things") => Book 1 successfully created Book.create( :chapters => [ Chapter.new(:title => "Introduction"), Chapter.new(:title => "Destroy things") => Book 2 fails to validate second_book = Book.create( :chapters => [ Chapter.new(:title => "A temporary Introduction title"), Chapter.new(:title => "Destroy things") => Book 2 succesfully created second_book.chapters[0].title= "Introduction" => success second_book.chapters.save => success second_book.save => success Can anyone shed some light on how to do this? Or why it's happening?

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  • Finding the unique paths through a Neo4j graph

    - by Larry
    I have a Neo4j graph with 12 inputs and 4 outputs, and am trying to write a query with the Java Traverser that will return the 14 unique paths from an input to an output node. All the queries I have tried return only a subset of the 14 paths. For example, the code below returns 4 paths, but the other 10 all stop 1 node short of the output. RelationshipType relType = RelationshipTypes.EDGE; TraversalDescription td = new TraversalDescriptionImpl() .depthFirst() .relationships(relType, Direction.OUTGOING); for (Node node : inputs){ Traverser tv = td.traverse(node); Iterator<Path> iter = tv.iterator(); // ... print path } I've tried uniqueness and depth settings as well, with no effect. The query below returns all 14 paths using the web interface, but when I use the ExecutionEngine class, I only get 13 paths back. START s=node(*) MATCH (s)-[p:EDGE*]->(c) WHERE s.type! = "INPUT" AND c.type! = "OUTPUT" RETURN p How do I get all the unique paths using the Java API?

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  • [Rails] Accessing error_messages on form_tag

    - by aaronrussell
    I have built a custom form for creating a joining model on a has_many :through relationship. The models look roughly like this: class Team has_many :team_members has_many :members, :through => :team_members end class Member has_many :team_members has_many :teams, :through => :team_members end class TeamMember belongs_to :team belongs_to :member # and this model has some validations too end The form I have built is for selecting which members should be in a team. I won't paste the form, but it uses the form_tag method and basically sends an array of hashes which contain a member_id and a squad_number. I then update the database with an action that looks roughly like this (simplified a bit, but you get the jist): @team.transaction do @team.team_members = params[:team_members].collect{|tm| @team.team_members.new(tm)} if @team.save redirect_to ... else render :action => :members end end Everything works great but I am validating the squad_number for uniqueness and numerically. So, when any of those validations fail, how do I get access to them in my view, and how do I ascertain which of the many members it has failed on?

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