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  • Deleting a user > need to also delete their project, and then activities for that project? (PHP, MyS

    - by Jamie
    Hi guys, Really stuck with this... basically my system has 4 tables; users, projects, user_projects and activities. The user table has a usertype field which defines whether or not they are admin or user (by an integer)... An admin can create a project, create an acitivity for the project and assign a user (limited access user) an activity. Therefore, this setup means that an admin is never directly associated with an activity (instead a project). When my head admin user deletes an admin, I need all projects and activities (for their projects) to be deleted also. My delete script for a user is simple so far and works, but I'm having trouble on how to gain the projectID in order to know which activities to remove (associated with the projects which are about to be deleted): $userid = $_GET['userid']; $query = "DELETE FROM users WHERE userid=".$userid; $result = mysql_query($sql, $connection) or die("Error: ".mysql_error()); $query = "DELETE FROM projects WHERE userid=".$userid; $result = mysql_query($sql, $connection) or die("Error: ".mysql_error()); $query = "DELETE FROM userprojects WHERE userid=".$userid; $result = mysql_query($sql, $connection) or die("Error: ".mysql_error()); $query = "DELETE FROM activities WHERE projectid=".$projectid; $result = mysql_query($sql, $connection) or die("Error: ".mysql_error()); Now the first three queries execute fine, obviously because the userid is being retrieved successfully. However the 4th and final query I know is wrong, because there is no projectid to be gained from anywhere, however I put it there to help understand what I am trying to get!! :D Im guessing that i would need something like 'WHERE projectid=' then something to gather the removed projects from the userid which can be related to the activities for that project(s)!! Its a simple concept but I'm having trouble...please excuse any bad code as I am learning also. Thanks for any help!

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  • Resources related to data-mining and gaming on social networks

    - by darren
    Hi all I'm interested in the problem of patterning mining among players of social networking games. For example detecting cheaters of a game, given a company's user database. So far I have been following the usual recipe for a data mining project: construct a data warehouse that aggregates significant information select a classifier, and train it with a subsectio of records from the warehouse validate classifier with another test set lather, rinse, repeat Surprisingly, I've found very little in this area regarding literature, best practices, etc. I am hoping to crowdsource the information gathering problem here. Specifically what I'm looking for: What classifiers have worked will for this type of pattern mining (it seems highly temporal, users playing games, users receiving rewards, users transferring prizes etc). Are there any highly agreed upon attributes specific to social networking / gaming data? What is a practical amount of information that should be considered? One problem I've run into is data overload, where queries and data cleansing may take days to complete. Related to point above, what hardware resources are required to produce results? I've found it difficult to estimate the amount of computing power I will require for production use. It has become apparent that a white box in the corner does not have enough horse-power for such a project. Are companies generally resorting to cloud solutions? Are they buying clusters? Basically, any resources (theoretical, academic, or practical) about implementing a social networking / gaming pattern-mining program would be very much appreciated. Thanks.

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  • Oracle command hangs when using view for "WHERE x IN..." subquery

    - by Calvin Fisher
    I'm working on a web service that fetches data from an oracle data source in chunks and passes it back to an indexing/search tool in XML format. I'm the C#/.NET guy, and am kind of fuzzy on parts of Oracle. Our Oracle team gave us the following script to run, and it works well: SELECT ROWID, [columns] FROM [table] WHERE ROWID IN ( SELECT ROWID FROM ( SELECT ROWID FROM [table] WHERE ROWID > '[previous_batch_last_rowid]' ORDER BY ROWID ) WHERE ROWNUM <= 10000 ) ORDER BY ROWID 10,000 rows is an arbitrary but reasonable chunk size and ROWID is sufficiently unique for our purposes to use as a UID since each indexing run hits only one table at a time. Bracketed values are filled in programmatically by the web service. Now we're going to start adding views to the indexing, each of which will union a few separate tables. Since ROWID would no longer function as a unique identifier, they added a column to the views (VIEW_UNIQUE_ID) that concatenates the ROWIDs from the component tables to construct a UID for each union. But this script does not work, even though it follows the same form as the previous one: SELECT VIEW_UNIQUE_ID, [columns] FROM [view] WHERE VIEW_UNIQUE_ID IN ( SELECT VIEW_UNIQUE_ID FROM ( SELECT VIEW_UNIQUE_ID FROM [view] WHERE ROWID > '[previous_batch_last_view_unique_id]' ORDER BY VIEW_UNIQUE_ID ) WHERE ROWNUM <= 10000 ) ORDER BY VIEW_UNIQUE_ID It hangs indefinitely with no response from the Oracle server. I've waited 20+ minutes and the SQLTools dialog box indicating a running query remains the same, with no progress or updates. I've tested each subquery independently and each works fine and takes a very short amount of time (<= 1 second), so the view itself is sound. But as soon as the inner two SELECT queries are added with "WHERE VIEW_UNIQUE_ID IN...", it hangs. Why doesn't this query work for views? In what important way are they not interchangeable here?

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • Help Converting T-SQL Query to LINQ Query

    - by campbelt
    I am new to LINQ, and so am struggle over some queries that I'm sure are pretty simple. In any case, I have been hiting my head against this for a while, but I'm stumped. Can anyone here help me convert this T-SQL query into a LINQ query? Once I see how it is done, I'm sure I'll have some question about the syntax: SELECT BlogTitle FROM Blogs b JOIN BlogComments bc ON b.BlogID = bc.BlogID WHERE b.Deleted = 0 AND b.Draft = 0 AND b.[Default] = 0 AND bc.Deleted = 0 GROUP BY BlogTitle ORDER BY MAX([bc].[Timestamp]) DESC Just to show that I have tried to solve this on my own, here is what I've come up with so far, though it doesn't compile, let alone work ... var iqueryable = from blog in db.Blogs join blogComment in db.BlogComments on blog.BlogID equals blogComment.BlogID where blog.Deleted == false && blog.Draft == false && blog.Default == false && blogComment.Deleted == false group blogComment by blog.BlogID into blogGroup orderby blogGroup.Max(blogComment => blogComment.Timestamp) select blogGroup;

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  • An error has occurred opening extern DTD (w3.org, xhtml1-transitional.dtd). 503 Server Unavailable

    - by Cheeso
    I'm trying to do xpath queries over an xhtml document. The document looks like this: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html lang="en" xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"> <head> .... </head> <body> ... </body> </html> Because the document includes various char entities (&nbsp; and so on), I need to use the DTD, in order to load it with an XmlReader. So my code looks like this: var reader = XmlReader.Create(sr, new XmlReaderSettings { ProhibitDtd = false }); But when I run this, it returns An error has occurred while opening external DTD 'http://www.w3.org/TR/xhtml1-transitional.dtd': The remote server returned an error: (503) Server Unavailable. Now, I know why I am getting the 503 error. W3C explained it very clearly. But I still want to validate the document. How can I validate with the DTD, and get the entity definitions, without hitting the w3.org website? related: - java.io.IOException: Server returned HTTP response code: 503

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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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  • 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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  • 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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  • MySQL performance

    - by kapil.israni
    Hi, I have this LAMP application with about 900k rows in MySQL and I am having some performance issues. Background - Apart from the LAMP stack , there's also a Java process (multi-threaded) that runs in its own JVM. So together with LAMP & java, they form the complete solution. The java process is responsible for inserts/updates and few selects as well. These inserts/updates are usually in bulk/batch, anywhere between 5-150 rows. The PHP front-end code only does SELECT's. Issue - the PHP/SELECT queries become very slow when the java process is running. When the java process is stopped, SELECT's perform alright. I mean the performance difference is huge. When the java process is running, any action performed on the php front-end results in 80% and more CPU usage for mysqld process. Any help would be appreciated. MySQL is running with default parameters & settings. Software stack - Apache - 2.2.x MySQL -5.1.37-1ubuntu5 PHP - 5.2.10 Java - 1.6.0_15 OS - Ubuntu 9.10 (karmic)

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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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  • SQL 2000 (MSDE) Hangs When It Receives an Erroneous Query from a Classic ASP Web Application

    - by Jimbo
    I have a SQL interface page in my classic ASP web app that allows admin users to run queries against the app's database (MSDE 2000) - it simply consists of a textarea that the user submits and the app returns the resulting list of records as below Dim oRS Set oRS = Server.CreateObject("ADODB.Recordset") oRS.ActiveConnection = sConnectionString // run the query - this is for the admin only so doesnt check for sql safe commands etc. oRS.Open Request.Form("txtSQL") If Not oRS.EOF Then // list the field names from the recordset For i = 0 to oRS.Fields.Count - 1 Response.Write oRS.Fields(i).name & "&nbsp;" Next // show the data for each record in the recordset While Not oRS.EOF For i = 0 to oRS.Fields.Count - 1 Response.Write oRS.Fields(i).value & "&nbsp;" Next Response.Write "<br />" oRS.Movenext() Wend End If The problem with this is that if you send it an invalid query (with a spelling mistake, invalid join etc.) instead of throwing back an error immediately, it hangs IIS (you can see this by trying to browse the app from another computer, it fails) for a number of minutes and THEN returns the error. I have NO idea why! Can anyone help?

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