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• LINQ to SQL : Too much CPU Usage: What happens when there are multiple users.

  - by soldieraman

  I am using LINQ to SQL and seeing my CPU Usage sky rocketting. See below screenshot. I have three questions What can I do to reduce this CPU Usage. I have done profiling and basically removed everything. Will making every LINQ to SQL statement into a compiled query help? I also find that even with compiled queries simple statements like ByID() can take 3 milliseconds on a server with 3.25GB RAM 3.17GHz - this will just become slower on a less powerful computer. Or will the compiled query get faster the more it is used? The CPU Usage (on the local server goes to 12-15%) for a single user will this multiply with the number of users accessing the server - when the application is put on a live server. i.e. 2 users at a time will mean 15*2 = 30% CPU Usage. If this is the case is my application limited to maximum 4-5 users at a time then. Or doesnt LINQ to SQL .net share some CPU usage.

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• getting base url of web site's root (absolute/relative url)

  - by uzay95

  I want to completely understand how to use relative and absolute url address in static and dynamic files. ~ : / : .. : in a relative URL indicates the parent directory . : refers to the current directory / : always replaces the entire pathname of the base URL // : always replaces everything from the hostname onwards This example is easy when you are working without virtual directory. But i am working on virtual directory. Relative URI Absolute URI about.html http://WebReference.com/html/about.html tutorial1/ http://WebReference.com/html/tutorial1/ tutorial1/2.html http://WebReference.com/html/tutorial1/2.html / http://WebReference.com/ //www.internet.com/ http://www.internet.com/ /experts/ http://WebReference.com/experts/ ../ http://WebReference.com/ ../experts/ http://WebReference.com/experts/ ../../../ http://WebReference.com/ ./ http://WebReference.com/html/ ./about.html http://WebReference.com/html/about.html I want to simulate a site below, like my project which is working on virtual directory. These are my aspx and ascx folder http://hostAddress:port/virtualDirectory/MainSite/ASPX/default.aspx http://hostAddress:port/virtualDirectory/MainSite/ASCX/UserCtrl/login.ascx http://hostAddress:port/virtualDirectory/AdminSite/ASPX/ASCX/default.aspx These are my JS Files(which will be use both with the aspx and ascx files): http://hostAddress:port/virtualDirectory/MainSite/JavascriptFolder/jsFile.js http://hostAddress:port/virtualDirectory/AdminSite/JavascriptFolder/jsFile.js this is my static web page address(I want to show some pictures and run inside some js functions): http://hostAddress:port/virtualDirectory/HTMLFiles/page.html this is my image folder http://hostAddress:port/virtualDirectory/Images/PNG/arrow.png http://hostAddress:port/virtualDirectory/Images/GIF/arrow.png if i want to write and image file's link in my ASPX file i should write aspxImgCtrl.ImageUrl = Server.MapPath("~")+"/Images/GIF/arrow.png"; But if i want to write the path hard coded or from javascript file, what kind of url address it should be?

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• Separating Javascript and Html, when dynamically adding html via javascript

  - by optician

  I am currently building a very dynamic table for a list application, which will basically perform basic CRUD functions via AJAX. What I would like to do is separate the visual design and javascript to the point where I can change the design side without touching the JS side. This would only work where the design stays roughly the same(i would like to use it for rapid protyping) Here is an example. <table> <tr><td>record-123</td><td>I am line 123</td><td>delete row</td></tr> <tr><td>record-124</td><td>I am line 124</td><td>delete row</td></tr> <tr><td>record-125</td><td>I am line 125</td><td>delete row</td></tr> <tr><td>add new record</td></tr> </table> Now, when I add a new record, I would like to insert a new row of html, but I would rather not put this html into the javascript file. What I am considering is creating a row like this on the page, near the table. <tr style='visble:none;' id='template-row'><td>record-id</td><td>content-area</td><td>delete row</td></tr> And when I come to add the new row, I search the page for the tags with the id=template-row , and then grab it, do a string replace on it, and then put it in the right place in the page. As long as the design doesn't shift radically, and I keep the placeholder strings the same, it means designs can be quickly modified without touching the js. Can any give any advice on a methodology like this?

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• Memory allocation error from MySql ODBC 5.1 driver in C# application on insert statement

  - by Chinjoo

  I have a .NET Wndows application in C#. It's a simple Windows application that is using the MySql 5.1 database community edition. I've downloaded the MySql ODBC driver and have created a dsn to my database on my local machine. On my application, I can perform get type queries without problems, but when I execute a given insert statement (not that I've tried doing any others), I get the following error: {"ERROR [HY001] [MySQL][ODBC 5.1 Driver][mysqld-5.0.27-community-nt]Memory allocation error"} I'm running on a Windows XP machine. My machine has 1 GB of memory. Anyone have any ideas? See code below OdbcConnection MyConn = DBConnection.getDBConnection(); int result = -1; try { MyConn.Open(); OdbcCommand myCmd = new OdbcCommand(); myCmd.Connection = MyConn; myCmd.CommandType = CommandType.Text; OdbcParameter userName = new OdbcParameter("@UserName", u.UserName); OdbcParameter password = new OdbcParameter("@Password", u.Password); OdbcParameter firstName = new OdbcParameter("@FirstName", u.FirstName); OdbcParameter LastName = new OdbcParameter("@LastName", u.LastName); OdbcParameter sex = new OdbcParameter("@sex", u.Sex); myCmd.Parameters.Add(userName); myCmd.Parameters.Add(password); myCmd.Parameters.Add(firstName); myCmd.Parameters.Add(LastName); myCmd.Parameters.Add(sex); myCmd.CommandText = mySqlQueries.insertChatUser; result = myCmd.ExecuteNonQuery(); } catch (Exception e) { //{"ERROR [HY001] [MySQL][ODBC 5.1 Driver][mysqld-5.0.27-community-nt]Memory // allocation error"} EXCEPTION ALWAYS THROWN HERE } finally { try { if (MyConn != null) MyConn.Close(); } finally { } }

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• MySQL use certain columns, based on other columns

  - by Rabbott

  I have this query: SELECT COUNT(articles.id) AS count FROM articles, xml_documents, streams WHERE articles.xml_document_id = xml_documents.id AND xml_documents.stream_id = streams.id AND articles.published_at BETWEEN '2010-01-01' AND '2010-04-01' AND streams.brand_id = 7 Which just uses the default equajoin by specifying three tables in csv format in the FROM clause.. What I need to do is group this by a value found within articles.source (raw xml).. so it could turn into this: SELECT COUNT(articles.id) AS count, ExtractValue(articles.source, "/article/media_type") AS media_type FROM articles, xml_documents, streams WHERE articles.xml_document_id = xml_documents.id AND xml_documents.stream_id = streams.id AND articles.published_at BETWEEN '2010-01-01' AND '2010-04-01' AND streams.brand_id = 7 GROUP BY media_type which works fine, the problem is, I'm using rails, and using STI for the xml_documents table. The articles.source that is provided to the ExtractValue method will be of a couple different formats.. So what I need to be able to do is use "/article/media_type" IF xml_documents.type = 'source one' and use "/article/source" if xml_documents.type = 'source two' This is just because the two document types format their XML differently, but I don't want to have to run multiple queries to retrieve this information.. It would be nice if one could use a ternary operator, but i don't think this is possible.. EDIT At this Point I am looking at making a temp table, or simply using UNION to place multiple result sets together..

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• Any way to avoid creating a huge C# COM interface wrapper when only a few methods needed?

  - by Paul Accisano

  Greetings all, I’m working on a C# program that requires being able to get the index of the hot item in Windows 7 Explorer’s new ItemsView control. Fortunately, Microsoft has provided a way to do this through UI Automation, by querying custom properties of the control. Unfortunately, the System.Windows.Automation namespace inexplicably does not seem to provide a way to query custom properties! This leaves me with the undesirable position of having to completely ditch the C# Automation namespace and use only the unmanaged COM version. One way to do it would be to put all the Automation code in a separate C++/CLI module and call it from my C# application. However, I would like to avoid this option if possible, as it adds more files to my project, and I’d have to worry about 32/64-bit problems and such. The other option is to make use of the ComImport attribute to declare the relevant interfaces and do everything through COM-interop. This is what I would like to do. However, the relevant interfaces, such as IUIAutomation and IUIAutomationElement, are FREAKING HUGE. They have hundreds of methods in total, and reference tons and tons of interfaces (which I assume I would have to also declare), almost all of which I will never ever use. I don’t think the UI Automation interfaces are declared in any Type Library either, so I can’t use TLBIMP. Is there any way I can avoid having to manually translate a bajillion method signatures into C# and instead only declare the ten or so methods I actually need? I see that C# 4.0 added a new “dynamic” type that is supposed to ease COM interop; is that at all relevant to my problem? Thanks

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• Understanding WordProcessingML tags and avoid unnecessary tags

  - by rithanyalaxmi

  Hi, I am using MS Word API to generate .docx which contains the data fetched from DB, in which i am applying the respective styles, fonts, symbols, etc. If the data fetched from the DB is quite huge, then there is a problem in displaying those data in the .docx file. I found that internally MS Word 2007 will write some content through tags which may not be needed to display the data. Hence i am figuring out what are the necessary MS Word tags needed when converting into a .xml file. So that i can avoid unnecessary tags and build only the respective tags which are needed to display the data. Hence i am planning to write my own .xml with the MS Word tags which are needed, than generating a .XML from .docx file My queries are:- 1) Whether it is right that the MS Word will generate some tags which may not be needed during the conversion of .docx to document.xml? That makes it heavy? If so what are the tags , so that i can avoid them when write by own .xml file. 2) Please send links to understand about the MS Word tags and its advantages, which tags are needed and which are not ? 3) Whether my approach to write a new .xml similar to document.xml (.docx conversion) is worthy one to go forward so that i can build the .xml with the tags i needed , so that i can improve the performance of the data display? Please shed some light into it and thanks in advance.. Thanks, Rithu

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• Sql Query - Selecting rows where user can be both friend and user

  - by Gublooo

  Hey Sorry the title is not very clear. This is a follow up to my earlier question where one of the members helped me with a query. I have a following friends Table Friend friend_id - primary key user_id user_id_friend status The way the table is populated is - when I send a friend request to John - my userID appears in user_id and Johns userID appears in user_id_friend. Now another scenario is say Mike sends me a friend request - in this case mike's userID will appear in user_id and my userID will appear in user_id_friend So to find all my friends - I need to run a query to find where my userID appears in both user_id column as well as user_id_friend column What I am trying to do now is - when I search for user say John - I want all users Johns listed on my site to show up along with the status of whether they are my friend or not and if they are not - then show a "Add Friend" button. Based on the previous post - I got this query which does part of the job - My example user_id is 1: SELECT u.user_id, f.status FROM user u LEFT OUTER JOIN friend f ON f.user_id = u.user_id and f.user_id_friend = 1 where u.name like '%' So this only shows users with whom I am friends where they have sent me request ie my userID appears in user_id_friend. Although I am friends with others (where my userID appears in user_id column) - this query will return that as null To get those I need another query like this SELECT u.user_id, f.status FROM user u LEFT OUTER JOIN friend f ON f.user_id_friend = u.user_id and f.user_id = 1 where u.name like '%' So how do I combine these queries to return 1 set of users and what my friendship status with them is. I hope my question is clear Thanks

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• Why is my mssql query failing?

  - by Eric Reynolds

  connect(); $arr = mssql_fetch_assoc(mssql_query("SELECT Applications.ProductName, Applications.ProductVersion, Applications.ProductSize, Applications.Description, Applications.ProductKey, Applications.ProductKeyID, Applications.AutomatedInstaller, Applications.AutomatedInstallerName, Applications.ISO, Applications.ISOName, Applications.Internet, Applications.InternetURL, Applications.DatePublished, Applications.LicenseID, Applications.InstallationGuide, Vendors.VendorName FROM Applications INNER JOIN Vendors ON Applications.VendorID = Vendors.VendorID WHERE ApplicationID = ".$ApplicationID)); $query1 = mssql_query("SELECT Issues.AppID, Issues.KnownIssues FROM Issues WHERE Issues.AppID=".$ApplicationID); $issues = mssql_fetch_assoc($query1); $query2 = mssql_query("SELECT ApplicationInfo.AppID, ApplicationInfo.Support_Status, ApplicationInfo.UD_Training, ApplicationInfo.AtomicTraining, ApplicationInfo.VendorURL FROM software.software_dbo.ApplicationInfo WHERE ApplicationInfo.AppID = ".$ApplicationID); $row = mssql_fetch_assoc($query2); function connect(){ $connect = mssql_connect(DBSERVER, DBO, DBPW) or die("Unable to connect to server"); $selected = mssql_select_db(DBNAME, $connect) or die("Unable to connect to database"); return $connect; } Above is the code. The first query/fetch_assoc works perfectly fine, however the next 2 queries fail and I cannot figure out why. Here is the error statement that shows up from php: Warning: mssql_query() [function.mssql-query]: message: Invalid object name 'Issues'. (severity 16) in /srv/www/htdocs/agreement.php on line 47 Warning: mssql_query() [function.mssql-query]: General SQL Server error: Check messages from the SQL Server (severity 16) in /srv/www/htdocs/agreement.php on line 47 Warning: mssql_query() [function.mssql-query]: Query failed in /srv/www/htdocs/agreement.php on line 47 Warning: mssql_fetch_assoc(): supplied argument is not a valid MS SQL-result resource in /srv/www/htdocs/agreement.php on line 48 Warning: mssql_query() [function.mssql-query]: message: Invalid object name 'software.software_dbo.ApplicationInfo'. (severity 16) in /srv/www/htdocs/agreement.php on line 51 Warning: mssql_query() [function.mssql-query]: General SQL Server error: Check messages from the SQL Server (severity 16) in /srv/www/htdocs/agreement.php on line 51 Warning: mssql_query() [function.mssql-query]: Query failed in /srv/www/htdocs/agreement.php on line 51 Warning: mssql_fetch_assoc(): supplied argument is not a valid MS SQL-result resource in /srv/www/htdocs/agreement.php on line 52 The error clearly centers around the fact that the query is not executing. In my database I have a table called Issues and a table called ApplicationInfo so I am unsure why it is telling me that they are invalid objects. Any help would be appreciated. Thanks, Eric R.

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• Retrieving varbinary output from a query in sql server into classic ASP

  - by user303526

  Hi, I'm trying to retrieve a varbinary output value from a query running on SQL Server 2005 into Classic ASP. The ASP execution just fails when it comes to part of code that is simply taking a varbinary output into a string. So I guess we gotta handle it some other way. Actually, I'm trying to set (sp_setapprole) and unset (sp_unsetapprole) application roles for a database connection. First I'd set the approle, then I'd run my required queries and finally unset the approle. During unsetting is when I need the cookie (varbinary) value in my ASP code so that I can create a query like 'exec sp_unsetapprole @cookie'. Well at this stage, I don't have the cookie (varbinary) value. The reason I'm doing this is I used to get 'sp_setapprole was not invoked correctly' error when trying to set app roles. I've disabled pooling by appending 'OLE DB Services = -2;Pooling=False' into my connection string. I know pooling helps performance wise but here I'm facing big problems. Please help me out to retrieve a varbinary value into an classic ASP file or suggest a way to set & unset app roles. Either way solutions are appreciated. Thanks, Nandagopal

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• Oracle XMLDB's XMLCAST and XMLQUERY incompatible with iBatis?

  - by tthong

  I've been trying to select a list of values from XMLs stored in an XMLType column but I keep getting the errors which are listed at the tail end of this post. The select id is getXMLFragment , and the relevant subset of the sqlmap.xml is as follows: <select id="getXMLFragment" resultClass="list"> SELECT XMLCAST(XMLQUERY('$CUSTOMER/CUSTOMER/DETAILS/ CUST_NAME/text()' PASSING CUSTOMER AS "CUSTOMER" RETURNING CONTENT) AS VARCHAR2(20)) AS customers FROM SHOP.CLIENT_INFO </select> (CUSTOMER is an XMLType column in CLIENT_INFO) and I call the statement using List<String> custNames= (List<String>) sqlMap.queryForList("getXMLFragment"); I am using ibatis-2.3.4.726.jar. Is it because iBatis does not recognise XMLDB queries and hence, tokenizes the string wrongly? On a sidenote, I have implemented XMLTypeCallback.java to handle XMLType insertions successfully, and I think it will work should I wish to retrieve the entire XML. However, in this case, I need to extract only individual values due to requirements. A workaround would be greatly appreciated. Thanks in advance. The exceptions generated are listed below: --- The error occurred in sqlMap.xml. --- The error occurred while preparing the mapped statement for execution. --- Check the getXMLFragment. --- Check the SQL statement. --- Cause: java.util.NoSuchElementException at com.ibatis.sqlmap.engine.mapping.statement.MappedStatement.executeQueryWithCallback(MappedStatement.java: 204) at com.ibatis.sqlmap.engine.mapping.statement.MappedStatement.executeQueryForList(MappedStatement.java: 139) at com.ibatis.sqlmap.engine.impl.SqlMapExecutorDelegate.queryForList(SqlMapExecutorDelegate.java: 567) at com.ibatis.sqlmap.engine.impl.SqlMapExecutorDelegate.queryForList(SqlMapExecutorDelegate.java: 541) at com.ibatis.sqlmap.engine.impl.SqlMapSessionImpl.queryForList(SqlMapSessionImpl.java: 118) at com.ibatis.sqlmap.engine.impl.SqlMapSessionImpl.queryForList(SqlMapSessionImpl.java: 122) at com.ibatis.sqlmap.engine.impl.SqlMapClientImpl.queryForList(SqlMapClientImpl.java: 98) at Main.main(Main.java:60) Caused by: java.util.NoSuchElementException at java.util.StringTokenizer.nextToken(StringTokenizer.java:332) at com.ibatis.sqlmap.engine.mapping.sql.simple.SimpleDynamicSql.processDynamicElements(SimpleDynamicSql.java: 90) at com.ibatis.sqlmap.engine.mapping.sql.simple.SimpleDynamicSql.getSql(SimpleDynamicSql.java: 45) at com.ibatis.sqlmap.engine.mapping.statement.MappedStatement.executeQueryWithCallback(MappedStatement.java: 184) ... 7 more

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• LINQ self referencing query

  - by Chris

  I have the following SQL query: select p1.[id], p1.[useraccountid], p1.[subject], p1.[message], p1.[views], p1.[parentid], case when p2.[created] is null then p1.[created] else p2.[created] end as LastUpdate from forumposts p1 left join ( select parentid, max(created) as [created] from forumposts group by parentid ) p2 on p2.parentid = p1.id where p1.[parentid] is null order by LastUpdate desc Using the following class: public class ForumPost : PersistedObject { public int Views { get; set; } public string Message { get; set; } public string Subject { get; set; } public ForumPost Parent { get; set; } public UserAccount UserAccount { get; set; } public IList<ForumPost> Replies { get; set; } } How would I replicate such a query in LINQ? I've tried several variations, but I seem unable to get the correct join syntax. Is this simply a case of a query that is too complicated for LINQ? Can it be done using nested queries some how? The purpose of the query is to find the most recently updated posts i.e. replying to a post would bump it to the top of the list. Replies are defined by the ParentID column, which is self-referencing.

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• What are good NoSQL and non-relational database solutions for audit/logging database

  - by Juha Syrjälä

  What would be suitable database for following? I am especially interested about your experiences with non-relational NoSQL systems. Are they any good for this kind of usage, which system you have used and would recommend, or should I go with normal relational database (DB2)? I need to gather audit trail/logging type information from bunch of sources to a centralized server where I could generate reports efficiently and examine what is happening in the system. Typically a audit/logging event would consist always of some mandatory fields, for example globally unique id (some how generated by program that generated this event) timestamp event type (i.e. user logged in, error happened etc) some information about source (server1, server2) Additionally the event could contain 0-N key-value pairs, where value might be up to few kilobytes of text. It must run on Linux server It should work with high amount of data (100GB for example) it should support some kind of efficient full text search It should allow concurrent reading and writing It should be flexible to add new event types and add/remove key-value pairs to new events. Flexible=no changes should be required to database schema, application generating the events can just add new event types/new fields as needed. it should be efficient to make queries against database. For reporting and exploring what happened. For example: How many events with type=X occurred in some time period. Get all events where field A has value Y. Get all events with type X and field A has value 1 and field B is not 2 and event occurred in last 24h

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• Good grammar for date data type for recursive descent parser LL(1)

  - by Totophil

  I'm building a custom expression parser and evaluator for production enviroment to provide a limited DSL to the users. The parser itself as the DSL, need to be simple. The parser is going to be built in an exotic language that doesn't support dynamic expression parsing nor has any parser generator tools available. My decision is to go for recursive descent approach with LL(1) grammar, so that even programmers with no previous experience in evaluating expression could quickly learn how the code works. It has to handle mixed expressions made up of several data types: decimals, percentages, strings and dates. And dates in the format of dd/mm/yyyy are easy to confuse with a string of devision ops. Is where a good solution to this problem? My own solution that is aimed at keeping the parser simple involves prefixing dates with a special symbol, let's say apostrophe: <date> ::= <apostr><digit><digit>/<digit><digit>/<digit><digit><digit><digit> <apostr> ::= ' <digit> ::= '0'..'9'

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• Design patter to keep track UITableView rows correspondance to underlying data in constant time.

  - by DenNukem

  When my model changes I want to animate changes in UITableView by inserting/deleting rows. For that I need to know the ordinal of the given row (so I can construct NSIndexPath), which I find hard to do in better-than-linear time. For example, consider that I have a list of addressbook entries which are manualy sorted by the user, i.e. there is no ordering "key" that represents the sort order. There is also a corresponding UITableView that shows one row per addressbook entry. When UITableView queries the datasource I query the NSMUtableArray populated with my entries and return required data in constant time for each row. However, if there is a change in underlying model I am getting a notification "Joe Smith, id#123 has been removed". Now I have a dilemma. A naive approach would be to scan the array, determine the index at which Joe Smith is and then ask UITableView to remove that precise row from the view, also removing it form the array. However, the scan will take linear time to finish. Now I could have an NSDictionary which allows me to find Joe Smith in constant time, but that doesn't do me a lot of good because I still need to find his ordinal index within the array in order to instruct UITableView to remove that row, which is again a linear search. I could further decide to store each object's ordinal inside the object itself to make it constant, but it will become outdated after first such update as all subsequent index values will have changed due to removal of an object. So what is the correct design pattern to accurately reflect model changes in the UITableView in costant (or at least logarithmic) time?

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• Hibernate "JOIN ... ON"?

  - by CaptainAwesomePants

  I have an application that uses Hibernate for its domain objects. One part of the app is common between a few apps, and it has no knowledge of the other systems. In order to handle relations, our class looks like this: @Entity public class SystemEvent { @Id @GeneratedValue public int entity_id; @Column(name="event_type") public String eventType; @Column(name="related_id") public int relatedObjectId; } relatedObjectId holds a foreign key to one of several different objects, depending on the type of event. When a system wants to know about events that are relevant to its interests, it grabs all the system events with eventType "NewAccounts" or some such thing, and it knows that all of those relatedObjectIds are IDs to a "User" object or similar. Unfortunately, this has caused a problem down the line. I can't figure out a way to tell Hibernate about this mapping, which means that HQL queries can't do joins. I'd really like to create an HQL query that looks like this: SELECT users FROM SystemEvent event join Users newUsers where event.eventType = 'SignUp' However, Hibernate has no knowledge of the relationship between SystemEvent and Users, and as far as I can tell, there's no way to tell it. So here's my question: Is there any way to tell Hibernate about a relationship when your domain objects reference each other via ID numbers and not class references?

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• WCF for a shared data access

  - by Audrius

  Hi all, I have a little experience with WCF and would like to get your opinion/suggestion on how the following problem can be solved: A web service needs to be accessible from multiple clients simultaneously and service needs to return a result from a shared data set. The concrete project I'm working on has to store a list of IP addresses/ranges. This list will be queried by a bunch of web servers for a validation purposes and we speak of a couple of thousand or more queries per minute. My initial draft approach was to use Windows service as a WCF host with service contract implementing class that is decorated with ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Multiple) that has a list object and a custom locking for accessing it. So basically I have a WCF service singleton with a list = shared data - multiple clients. What I do not like about it is that data and communication layers are merged into one and performance wise this doesn't feel "right". What I really really (- want is Windows service running an instance of IP list holding container class object, a second service running WCF service contract implementation and a way the latter querying the former in a nice way with a minimal blocking. Using another WCF channel would not really take me far away from the initial draft implementation or would it? What approach would you take? Project is still in a very early stage so complete design re-do is not out of question. All ideas are appreciated. Thanks! UPDATE: The data set will be changed dynamically. Web service will have a separate method to add IP or IP range and on top of that there will be a scheduled task that will trigger data cleanup every 10-15 minutes according to some rules. UPDATE 2: a separate benchmark project will be kicked up that should use MSSQL as a data backend (instead on in-memory list).

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• How can parallelism affect number of results?

  - by spender

  I have a fairly complex query that looks something like this: create table Items(SomeOtherTableID int,SomeField int) create table SomeOtherTable(Id int,GroupID int) with cte1 as ( select SomeOtherTableID,COUNT(*) SubItemCount from Items t where t.SomeField is not null group by SomeOtherTableID ),cte2 as ( select tc.SomeOtherTableID,ROW_NUMBER() over (partition by a.GroupID order by tc.SubItemCount desc) SubItemRank from Items t inner join SomeOtherTable a on a.Id=t.SomeOtherTableID inner join cte1 tc on tc.SomeOtherTableID=t.SomeOtherTableID where t.SomeField is not null ),cte3 as ( select SomeOtherTableID from cte2 where SubItemRank=1 ) select * from cte3 t1 inner join cte3 t2 on t1.SomeOtherTableID<t2.SomeOtherTableID option (maxdop 1) The query is such that cte3 is filled with 6222 distinct results. In the final select, I am performing a cross join on cte3 with itself, (so that I can compare every value in the table with every other value in the table at a later point). Notice the final line : option (maxdop 1) Apparently, this switches off parallelism. So, with 6222 results rows in cte3, I would expect (6222*6221)/2, or 19353531 results in the subsequent cross joining select, and with the final maxdop line in place, that is indeed the case. However, when I remove the maxdop line, the number of results jumps to 19380454. I have 4 cores on my dev box. WTF? Can anyone explain why this is? Do I need to reconsider previous queries that cross join in this way?

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• NSXMLParser: how do I wait until loading has finished?

  - by Archagon

  Let's say I'm using NSXMLParser to load a level (stored as an XML document, obviously) into my iPhone game. NSXMLParser works by assigning a delegate and sending it messages at key moments. How do I ensure that my entire level is loaded before doing anything else? I know I can make my main class the delegate and implement parserDidEndDocument, but this feels very hacky. My main class shouldn't have to know anything about the way the parsing is done! On the other hand, if I make a separate class/delegate for parsing my level, my main class has no way of knowing when the parsing is finished, unless it queries the parsing class continuously or the parsing class sends it a message. Either way, the main class would be tied to the implementation of the parsing class. Can I hide all this event-driven business from the main class and simply make the parser return the level object when it's done? (i.e., newLevel = [[GameLevel alloc] initFromXML:xmlfile], which would in turn use NSXMLParser to load the level and then somehow return when finished.) At the moment, I'm using an external DOM parser, but I'm curious how this would be done with NSXMLParser. Sorry if this is a stupid question -- I'm a bit new to this!

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• Database structure - is mySQL the right choice?

  - by Industrial

  Hi everyone, We are currently planning the database structure of a quite complex e-commerce web app that has flexibility as it's main cornerstone. Our app features a large amount of data (products) and we have run into a slight headache trying to keep performance high without compromizing normalization rules in the database, or leaving our highly beloved flexibility concept behind when integrating product options (also widely known as product attributes or parameters). Based on various references and sources available, we have made up lists on pros and cons of all major and well known database patterns to solve this. After comparing these, we have come up with two final alternatives: EAV (Entity-attribute-value model) : Pros: Database is used for all sorting. Cons: All related queries will include a number of joins between multiple tables in order to complete the collection of data. SLOB (Serialized LOB, also known as Facade?) : Pros: Very flexible. Keeping the number of necessary joins low compared to a EAV design pattern. Easy to update/add/remove data from each product. Cons: All sorting will be done by the application instead of the database. Will use lots of performance (memory?) when big datasets is processed by a large number of users. Our main questions: Which pattern/structure would you use, or maybe even a different solution? Is there better databases besides mySQL available nowadays to accomplish what we want? Thanks a lot! Reference: http://stackoverflow.com/questions/695752/product-table-many-kinds-of-product-each-product-has-many-parameters

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• Books and resources for Java Performance tuning - when working with databases, huge lists

  - by Arvind

  Hi All, I am relatively new to working on huge applications in Java. I am working on a Java web service which is pretty heavily used by various clients. The service basically queries the database (hibernate) and then works with a lot of Lists (there are adapters to convert list returned from DB to the interface which the service publishes) and I am seeing lot of issues with the service like high CPU usage or high heap space. While I can troubleshoot the performance issues using a profiler, I want to actually learn about what all I need to take care when I actually write code. Like what kind of List to use or things like using StringBuilder instead of String, etc... Is there any book or blogs which I can refer which will help me while I write new services? Also my application is multithreaded - each service call from a client is a new thread, and I want to know some best practices around that area as well. I did search the web but I found many tips which are not relevant in the latest Java 6 releases, so wanted to know what kind of resources would help a developer starting out now on Java for heavily used applications. Arvind

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• Hidden features of Perl?

  - by Adam Bellaire

  What are some really useful but esoteric language features in Perl that you've actually been able to employ to do useful work? Guidelines: Try to limit answers to the Perl core and not CPAN Please give an example and a short description Hidden Features also found in other languages' Hidden Features: (These are all from Corion's answer) C# Duff's Device Portability and Standardness Quotes for whitespace delimited lists and strings Aliasable namespaces Java Static Initalizers JavaScript Functions are First Class citizens Block scope and closure Calling methods and accessors indirectly through a variable Ruby Defining methods through code PHP Pervasive online documentation Magic methods Symbolic references Python One line value swapping Ability to replace even core functions with your own functionality Other Hidden Features: Operators: The bool quasi-operator The flip-flop operator Also used for list construction The ++ and unary - operators work on strings The repetition operator The spaceship operator The || operator (and // operator) to select from a set of choices The diamond operator Special cases of the m// operator The tilde-tilde "operator" Quoting constructs: The qw operator Letters can be used as quote delimiters in q{}-like constructs Quoting mechanisms Syntax and Names: There can be a space after a sigil You can give subs numeric names with symbolic references Legal trailing commas Grouped Integer Literals hash slices Populating keys of a hash from an array Modules, Pragmas, and command-line options: use strict and use warnings Taint checking Esoteric use of -n and -p CPAN overload::constant IO::Handle module Safe compartments Attributes Variables: Autovivification The $[ variable tie Dynamic Scoping Variable swapping with a single statement Loops and flow control: Magic goto for on a single variable continue clause Desperation mode Regular expressions: The \G anchor (?{}) and '(??{})` in regexes Other features: The debugger Special code blocks such as BEGIN, CHECK, and END The DATA block New Block Operations Source Filters Signal Hooks map (twice) Wrapping built-in functions The eof function The dbmopen function Turning warnings into errors Other tricks, and meta-answers: cat files, decompressing gzips if needed Perl Tips See Also: Hidden features of C Hidden features of C# Hidden features of C++ Hidden features of Java Hidden features of JavaScript Hidden features of Ruby Hidden features of PHP Hidden features of Python

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• Rails add a param to the end of a search query

  - by bob

  Hello, I am trying to implement a sort on the returned results of a search with rails. Filter by: 'recent' % | 'lowest_price' % | 'highest_price' % here are my links. I would like to add a filter to the end of my search query. So for example, I submit a search and I get back results and in my url I have http://localhost:3000/junks?search=handbag&condition=&category=&main_submit=Go! I would then like the user to be able to click one of the above links and have the page come back with a new query (i have this set up in the controller like such) con_id = params[:condition] if params[:category].nil? || params[:category].empty? cat_id = params[:category] results = Junk.search params[:search], :with => { :category_id => cat_id, :condition_id => con_id } case params[:filter] when "lowest_price" @junks = results.lowest_price.paginate :page => params[:page], :per_page => 12 when "highest_price" @junks = results.highest_price.paginate :page => params[:page], :per_page => 12 else @junks = results.paginate :page => params[:page], :per_page => 12 end else I would like the user to be able to click on of the above links and append a filter param to the end of the search query so that my controller can pick it up and call the correct database queries as seen in the case statement above. I'm guessing the url will look like this http://localhost:3000/junks?search=handbag&condition=&category=&main_submit=Go!&filter="lowest_price" How can I do this? Is there a better way?

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• ASP.NET MVC, Url Routing: Maximum Path (URL) Length

  - by Martin Aatmaa

  The Scenario I have an application where we took the good old query string URL structure: ?x=1&y=2&z=3&a=4&b=5&c=6 and changed it into a path structure: /x/1/y/2/z/3/a/4/b/5/c/6 We're using ASP.NET MVC and (naturally) ASP.NET routing. The Problem The problem is that our parameters are dynamic, and there is (theoretically) no limit to the amount of parameters that we need to accommodate for. This is all fine until we got hit by the following train: HTTP Error 400.0 - Bad Request ASP.NET detected invalid characters in the URL. IIS would throw this error when our URL got past a certain length. The Nitty Gritty Here's what we found out: This is not an IIS problem IIS does have a max path length limit, but the above error is not this. Learn dot iis dot net How to Use Request Filtering Section "Filter Based on Request Limits" If the path was too long for IIS, it would throw a 404.14, not a 400.0. Besides, the IIS max path (and query) length are configurable: <requestLimits maxAllowedContentLength="30000000" maxUrl="260" maxQueryString="25" /> This is an ASP.NET Problem After some poking around: IIS Forums Thread: ASP.NET 2.0 maximum URL length? http://forums.iis.net/t/1105360.aspx it turns out that this is an ASP.NET (well, .NET really) problem. The shit of the matter is that, as far as I can tell, ASP.NET cannot handle paths longer than 260 characters. The nail in the coffin in that this is confirmed by Phil the Haack himself: Stack Overflow ASP.NET url MAX_PATH limit Question ID 265251 The Question So what's the question? The question is, how big of a limitation is this? For my app, it's a deal killer. For most apps, it's probably a non-issue. What about disclosure? No where where ASP.NET Routing is mentioned have I ever heard a peep about this limitation. The fact that ASP.NET MVC uses ASP.NET routing makes the impact of this even bigger. What do you think?

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• Displaying single-instance business object data on SSRS

  - by Lachlan

  I have a SQL Server Reporting Services local (i.e. RDLC) report displayed in a ReportViewer, with two subreports. I am using business objects to populate the datasets. What is the best way to populate single-instance data on my report, e.g. a dynamic title, or a text box that lists a calculated value, not based on the report data? I am currently displaying data using the following style: public class MyRecordList { string Name { get; set; } List<MyRecord> Records { get; set;} } public MyRecord { string Description { get; set;} string Value { get; set;} } I set the datasource to the Records in an instance of MyRecordsList, and they print out find in a table. But adding a textbox and and referring to Name displays nothing. I also tried turning Name into a List, and referring to the first in the list, using: =First(Fields!Name.Value, "Report1_MyRecordList") but still nothing is printed on the report.

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