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  • Best practice: How to persist simple data without a database in django?

    - by Infinity
    I'm building a website that doesn't require a database because a REST API "is the database". (Except you don't want to be putting site-specific things in there, since the API is used by mostly mobile clients) However there's a few things that normally would be put in a database, for example the "jobs" page. You have master list view, and the detail views for each job, and it should be easy to add new job entries. (not necessarily via a CMS, but that would be awesome) e.g. example.com/careers/ and example.com/careers/77/ I could just hardcode this stuff in templates, but that's no DRY- you have to update the master template and the detail template every time. What do you guys think? Maybe a YAML file? Or any better ideas? Thx

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  • Is it possible to implement a lightweight database using Blackberry Persistance options?

    - by Tobias
    First I would like to explain why I want to use alternate Blackberry Persistance options rather than a Blackberry database itself, say SQLite. The reason is that the application i'm designing, I want it to be used in all the previous versions of Blackberry rather than just the ones having OS 5.0 or greater. Now, coming back to the actual question, I have got a database that I want to replicate to be used in the Blackberry application. The database has 8 tables and each table has approximately 12 different columns. One of the table has 1000 rows. Now if I was to implement this DB for a Blackberry application , keeping in mind that it will work on all the versions of Blackberry, what would be the best way to implement it?

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  • Is C# compiler not reporting all errors at once at each compile?

    - by Joan Venge
    When I am compiling this project, it show like 400+ errors in the Error List window, then I go to error sites, fix some, and the number goes to say 120+ errors, and then after fixing some more, the next compile reports like 400+ again. I can see that different files are coming in in the Error List window, so I am thinking the compiler aborts after a certain number of errors? If so, what's the reason for this? Is it not supposed to gather all the errors that are present in the project even if they are over 10K+?

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  • How to ReHash a password stored into my Database ? (PHP)

    - by Vincent Roye
    Hi! I have some passwords encrypted in my database and I would like to find a way to display them. Here is how they are saved into my mysql database: function generateHash($plainText, $salt = null){ if ($salt === null) { $salt = substr(md5(uniqid(rand(), true)), 0, 25); } else { $salt = substr($salt, 0, 25); } return $salt . sha1($salt . $plainText); } $secure_pass = generateHash($this->clean_password); Then $secure_pass is saved into my database. Anyone would have an idea ?? Thank you very much ;)

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  • Why do I have to set the max length of every damn text column in the database?

    - by John Leidegren
    Why is it that every RDBMS insists that you tell it what the max length of a text field is going to be... why can't it just infer this information form the data that's put into the database? I've mostly worked with MS SQL Server, but every other database I know also demands that you set these arbitrary limits on your data schema. The reality is that this is not particulay helpful or friendly to work with becuase the business requirements change all the time and almost every day some end-user is trying to put a lot of text into that column. Does any one with some inner working knowledge of a RDBMS know why we just don't infer the limits from the data that's put into the storage? I'm not talking about guessing the type information, but guessing the limits of a particular text column. I mean, there's a reason why I don't use nvarchar(max) on every text column in the database.

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  • SQL Server 2008 System Functions to Monitor the Instance, Database, Files, etc.

    SQL Server provides several system meta data functions which allow users to obtain property values of different SQL Server objects and securables. Although you can also use the SQL Server catalog views or Dynamic Management Views to obtain much of this information, in some circumstances the system meta data functions simplify the process. In this tip I am going to demonstrate some of the available system meta data functions and their usage in different scenarios.

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  • How to insert large files in mysql database using php? [closed]

    - by anjan
    Hi! I want to upload a large file of size 10M max to my mysql database. Using .htaccess i changed the PHP's own file upload limit to "10485760" = 10M, i am able to upload files upto 10M size without any problem. But i can not insert the file in database if it is more that 1M in size. i am using file_get_contents to read all file data and pass it to the insert query as a string to be inserted into a LONGBLOB field. But files with more than 1M size is not being added to database, though i can use print_r($_FILES) to examine that the file uploaded correctly. Any help will be appreciated and i will need it within next 6 hours. So, please help! best regards, Anjan * This is a duplicate of http://stackoverflow.com/questions/492549/how-can-i-insert-large-files-in-mysql-db-using-php *

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  • Why entered key word is not store in database?

    - by Nitz
    Hey Guys, I had made on form, in which i had one text area. Now i am storing that data of text area to mysql database. Now if i had press enter key word then it not stores in the database. Because i don't get exacted output as what i entered. as example... If i had write like this..... GoodMorningHow are you? then i only get like this... Good Morning How are you? So its not storing that enter key word in the database.

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  • Charts don't show up when subreport is included in group header in pentaho reporting 3.9.1-GA

    - by user2909808
    There is an issue concerning in sub-reports. I created a bar chart in report header. The sub report(inline) is placed in the Details of main report. In the sub report, the bar chart is placed in the group header. I imported the required parameters to the sub reports from the main report and also i have a sub query for the sub report.The expected output is to show an updated bar chart within each (inner) group of main report. However, the chart is only displayed in the last group occurence, although the chart area itself is allotted in every expected case. Can any one say me, what mistake i did.

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  • SQLite delete the last 25% of records in a database.

    - by Steven smethurst
    I am using a SQLite database to store values from a data logger. The data logger will eventually fills up all the available hard drive space on the computer. I'm looking for a way to remove the last 25% of the logs from the database once it reaches a certain limit. Using the following code: $ret = Query( 'SELECT id as last FROM data ORDER BY id desc LIMIT 1 ;' ); $last_id = $ret[0]['last'] ; $ret = Query( 'SELECT count( * ) as total FROM data' ); $start_id = $last_id - $ret[0]['total'] * 0.75 ; Query( 'DELETE FROM data WHERE id < '. round( $start_id, 0 ) ); A journal file gets created next to the database that fills up the remaining space on the drive until the script fails. How/Can I stop this journal file from being created? Anyway to combined all three SQL queries in to one statement?

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  • ????Oracle EBS R12 on Exadata V2 ,MMA and Hight Performance

    - by longchun.zhu
    ???????? ?????,???, ????????hands-on ??? ??????: 1. Oracle EBS R12 on Database Machine MAA & Performance Architecture. 2. Oracle EBS R12 Single Instance Node Deployment Procedure. 2.Start Rapid Install Wizard. 3. Oracle EBS R12 Single Instance Node Chinese Patch Update. 4.Applying Patches. 5.Upgrade Application Database Version to 11g Release 2. 6.Database Upgrade 7. Deploy Clone Application Database to Sun Oracle Database Machine. 8.Migrate Application Database File System to Exadata ASM Storage. 9.Covert Application Database Single Instance to RAC.. 10.Configure High Availability & High Performance Architecture with Exadata.

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  • Windows?? Oracle Database 11g Release 2 ? SAP ????????

    - by ?? ?
    2010?3?31??UNIX???Linux???????????????????????? 2010?6?9??Windows(32bit, x64)???????SAP??????????????? ?????Windows?2003?2008????????? ???ECC?????(7.02)??????????????? ??10g R2??????????????????11g R2????OK??????? (?????????UNIX/Linux/Windows??2010?????????)   SAP????? 1398634???????????????????????????????????? ??????PAM?????????????????????? SAP?????SAP/Oracle 11g???????????????????????????????

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  • ????: PostgreSQL??Oracle RAC????

    - by Kumiko Fujita
    ?????????????????????????????????????????????????????????????????????????? ????????????????????????? * * * ?????????????????????????????????????DBMS??????????????????????????????DBMS????????????????????????????????????????????? 1. ???? ?????????????????????????????????????????????????????????????????????1?????? ???????????????? ?????????????????????????????DB???????OSS?PostgreSQL?????AP?????DB??????????????????? ???????? ?????10?????????????GB????????????????????????????DB?????????????????????????? ?????????????3,500?????????24????????????????????????????????????? ??AP?????????????????????????????????????????DB??PostgreSQL??????????????????PostgreSQL ????????????????????Vacuum????????????????????????????????????????????????????? ??????????????????PostgreSQL?OSS??????????????????????????????????????????????????DB MS??????Oracle Database 11gR2???????????????????????500GB???????????????????????????Partitioning ???????? Oracle Database Enterprise Edition?????????????????????????????????????????????? ????SAN?????Active/Standby???HA????????????????? 2. ????? 2.1. ???? PostgreSQL??????Oracle??????????????????????????????????????????????????????TEXT????? ????????????????????Oracle??????????????????????????PostgreSQL??csv???????Oracle Database?SQL*Loa der????????????? ??????????????????????????????DB??????????????Windows?Liunx??????????????????????? ????????????????????????????????????????????????? ?????????????PostgreSQL?NULL?????''????????????Oracle Database???????????????????????? ?????????? table { border-collapse: collapse; } th { border: solid 1px #666666; color: #000000; background-color: #ff9999; } td { border: solid 1px #666666; color: #000000; background-color: #ffffff; } ???? PostgreSQL Oracle Database ??? CHAR(n) CHAR(n),CLOB VARCHAR(n) VARCHAR2(n),CLOB TEXT CLOB ??? NUMERIC NUMBER INTEGER NUMBER SMALLINT NUMBER BIGINT NUMBER REAL NUMBER DOUBLE PRECISION NUMBER ??? DATE DATE TIMESTAMP TIMESTAMP ????? Bytea BLOB LOB BFILE/SecureFiles ??? OID ROWID 2.2. ????? ?????????????PostgreSQL?Oracle Database??????????SQL???????????????????????????????????Postg reSQL?LIMIT?OFFSET??Oracle Database?????????????????????? LIMIT,OFFSET???SELECT?????? /* PostgreSQL LIMIT,OFFSET */ SELECT ??? FROM ????? ORDER BY ???? LIMIT 2 OFFSET 5; /* Oracle Database????? */ SELECT ??? FROM (SELECT ???, ROWNUM line_no FROM (SELECT??? FROM ????? OREDR BY ???? ) ) WHERE line_no BETWEEN 6 AND 7; ??????????????????????????????????????????????????????????????????????????? ?????????????????? ????????????????????????????????????????????????Oracle Database??????????????????????Oracle Database????WHERE??????????????????????????????????????????????????????WHERE?????????????????????? 3. ???? ???????????????????????30%~40%????????????????????80%????????????????????? ?ITpro???:???????4????? ??????????????????????????????????? ·?????·??????????????????????????? ·????????????????????????????? ????????????????????????????????????????? 3.1. ??????? ????????????????????????????????????????·??????????????????????????????????? ???????????????????????????????????????????????????????·?????????????????? ???????????????????????????? (1)???????????????????? (2)???????????????????????????????????????????? (3)??????????????? (4)???????????????????????????????? ???????????·???????????????????????????????????????????????????????????????? ????????????????????? ????????·?? table { border-collapse: collapse; } th { border: solid 1px #666666; color: #000000; background-color: #ff9999; } td { border: solid 1px #666666; color: #000000; background-color: #ffffff; } ?? ?? ?? (1) ?????????? ????????????·???????????????????????? (2) ???????????????????? ?????????????????????????????? (3) ?????4????????????????? ???????????????????????DB????????? (4) ??????????(3)???????? ???????????????????????? ?????????????????????GB???????????????????????????????????????????(3)?????????? ??????? ??????????????????????????????????????????????csv??????????SQL*Loader?Oracle Database?????????????????????Oracle Database???????????????????????????INSERT????????????? ???????????????????????????????????????????????????????????????????????????? ?????????????????????? 3.2. ????? ???????????????????????????????????????????????????????????????????????????? ????????????????????????????????????????????????????????????????????????????????????????????? ?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? 3.3. ????? ??????????????????????????????????????????????????????????????????????????? ??????????????????????? DBMS????????????????????????SQL??????????????????????????????????????????????????PostgreSQL?Oracle Database???????????MVCC?????????????????????????Read Committed??????????????????????????????????????????????????????????????????????????????????? ????????????????DBMS?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? 4. ??? PostgreSQL??Oracle Database?????????????????????????????? ????????????·????????????????????????????????????? ??????4???????????????????????·??????????????????? ???????????????????????????????????????????????? ?????????????????????????????????????????????DBMS???????????????????DBMS???????? ?????SQL?????????????????????????????DB???????????????????????????? ???????????????????????????DBMS?????????????????????????????????????????????????????? ??????????????????????????????

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  • A ToDynamic() Extension Method For Fluent Reflection

    - by Dixin
    Recently I needed to demonstrate some code with reflection, but I felt it inconvenient and tedious. To simplify the reflection coding, I created a ToDynamic() extension method. The source code can be downloaded from here. Problem One example for complex reflection is in LINQ to SQL. The DataContext class has a property Privider, and this Provider has an Execute() method, which executes the query expression and returns the result. Assume this Execute() needs to be invoked to query SQL Server database, then the following code will be expected: using (NorthwindDataContext database = new NorthwindDataContext()) { // Constructs the query. IQueryable<Product> query = database.Products.Where(product => product.ProductID > 0) .OrderBy(product => product.ProductName) .Take(2); // Executes the query. Here reflection is required, // because Provider, Execute(), and ReturnValue are not public members. IEnumerable<Product> results = database.Provider.Execute(query.Expression).ReturnValue; // Processes the results. foreach (Product product in results) { Console.WriteLine("{0}, {1}", product.ProductID, product.ProductName); } } Of course, this code cannot compile. And, no one wants to write code like this. Again, this is just an example of complex reflection. using (NorthwindDataContext database = new NorthwindDataContext()) { // Constructs the query. IQueryable<Product> query = database.Products.Where(product => product.ProductID > 0) .OrderBy(product => product.ProductName) .Take(2); // database.Provider PropertyInfo providerProperty = database.GetType().GetProperty( "Provider", BindingFlags.NonPublic | BindingFlags.GetProperty | BindingFlags.Instance); object provider = providerProperty.GetValue(database, null); // database.Provider.Execute(query.Expression) // Here GetMethod() cannot be directly used, // because Execute() is a explicitly implemented interface method. Assembly assembly = Assembly.Load("System.Data.Linq"); Type providerType = assembly.GetTypes().SingleOrDefault( type => type.FullName == "System.Data.Linq.Provider.IProvider"); InterfaceMapping mapping = provider.GetType().GetInterfaceMap(providerType); MethodInfo executeMethod = mapping.InterfaceMethods.Single(method => method.Name == "Execute"); IExecuteResult executeResult = executeMethod.Invoke(provider, new object[] { query.Expression }) as IExecuteResult; // database.Provider.Execute(query.Expression).ReturnValue IEnumerable<Product> results = executeResult.ReturnValue as IEnumerable<Product>; // Processes the results. foreach (Product product in results) { Console.WriteLine("{0}, {1}", product.ProductID, product.ProductName); } } This may be not straight forward enough. So here a solution will implement fluent reflection with a ToDynamic() extension method: IEnumerable<Product> results = database.ToDynamic() // Starts fluent reflection. .Provider.Execute(query.Expression).ReturnValue; C# 4.0 dynamic In this kind of scenarios, it is easy to have dynamic in mind, which enables developer to write whatever code after a dot: using (NorthwindDataContext database = new NorthwindDataContext()) { // Constructs the query. IQueryable<Product> query = database.Products.Where(product => product.ProductID > 0) .OrderBy(product => product.ProductName) .Take(2); // database.Provider dynamic dynamicDatabase = database; dynamic results = dynamicDatabase.Provider.Execute(query).ReturnValue; } This throws a RuntimeBinderException at runtime: 'System.Data.Linq.DataContext.Provider' is inaccessible due to its protection level. Here dynamic is able find the specified member. So the next thing is just writing some custom code to access the found member. .NET 4.0 DynamicObject, and DynamicWrapper<T> Where to put the custom code for dynamic? The answer is DynamicObject’s derived class. I first heard of DynamicObject from Anders Hejlsberg's video in PDC2008. It is very powerful, providing useful virtual methods to be overridden, like: TryGetMember() TrySetMember() TryInvokeMember() etc.  (In 2008 they are called GetMember, SetMember, etc., with different signature.) For example, if dynamicDatabase is a DynamicObject, then the following code: dynamicDatabase.Provider will invoke dynamicDatabase.TryGetMember() to do the actual work, where custom code can be put into. Now create a type to inherit DynamicObject: public class DynamicWrapper<T> : DynamicObject { private readonly bool _isValueType; private readonly Type _type; private T _value; // Not readonly, for value type scenarios. public DynamicWrapper(ref T value) // Uses ref in case of value type. { if (value == null) { throw new ArgumentNullException("value"); } this._value = value; this._type = value.GetType(); this._isValueType = this._type.IsValueType; } public override bool TryGetMember(GetMemberBinder binder, out object result) { // Searches in current type's public and non-public properties. PropertyInfo property = this._type.GetTypeProperty(binder.Name); if (property != null) { result = property.GetValue(this._value, null).ToDynamic(); return true; } // Searches in explicitly implemented properties for interface. MethodInfo method = this._type.GetInterfaceMethod(string.Concat("get_", binder.Name), null); if (method != null) { result = method.Invoke(this._value, null).ToDynamic(); return true; } // Searches in current type's public and non-public fields. FieldInfo field = this._type.GetTypeField(binder.Name); if (field != null) { result = field.GetValue(this._value).ToDynamic(); return true; } // Searches in base type's public and non-public properties. property = this._type.GetBaseProperty(binder.Name); if (property != null) { result = property.GetValue(this._value, null).ToDynamic(); return true; } // Searches in base type's public and non-public fields. field = this._type.GetBaseField(binder.Name); if (field != null) { result = field.GetValue(this._value).ToDynamic(); return true; } // The specified member is not found. result = null; return false; } // Other overridden methods are not listed. } In the above code, GetTypeProperty(), GetInterfaceMethod(), GetTypeField(), GetBaseProperty(), and GetBaseField() are extension methods for Type class. For example: internal static class TypeExtensions { internal static FieldInfo GetBaseField(this Type type, string name) { Type @base = type.BaseType; if (@base == null) { return null; } return @base.GetTypeField(name) ?? @base.GetBaseField(name); } internal static PropertyInfo GetBaseProperty(this Type type, string name) { Type @base = type.BaseType; if (@base == null) { return null; } return @base.GetTypeProperty(name) ?? @base.GetBaseProperty(name); } internal static MethodInfo GetInterfaceMethod(this Type type, string name, params object[] args) { return type.GetInterfaces().Select(type.GetInterfaceMap).SelectMany(mapping => mapping.TargetMethods) .FirstOrDefault( method => method.Name.Split('.').Last().Equals(name, StringComparison.Ordinal) && method.GetParameters().Count() == args.Length && method.GetParameters().Select( (parameter, index) => parameter.ParameterType.IsAssignableFrom(args[index].GetType())).Aggregate( true, (a, b) => a && b)); } internal static FieldInfo GetTypeField(this Type type, string name) { return type.GetFields( BindingFlags.GetField | BindingFlags.Instance | BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic).FirstOrDefault( field => field.Name.Equals(name, StringComparison.Ordinal)); } internal static PropertyInfo GetTypeProperty(this Type type, string name) { return type.GetProperties( BindingFlags.GetProperty | BindingFlags.Instance | BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic).FirstOrDefault( property => property.Name.Equals(name, StringComparison.Ordinal)); } // Other extension methods are not listed. } So now, when invoked, TryGetMember() searches the specified member and invoke it. The code can be written like this: dynamic dynamicDatabase = new DynamicWrapper<NorthwindDataContext>(ref database); dynamic dynamicReturnValue = dynamicDatabase.Provider.Execute(query.Expression).ReturnValue; This greatly simplified reflection. ToDynamic() and fluent reflection To make it even more straight forward, A ToDynamic() method is provided: public static class DynamicWrapperExtensions { public static dynamic ToDynamic<T>(this T value) { return new DynamicWrapper<T>(ref value); } } and a ToStatic() method is provided to unwrap the value: public class DynamicWrapper<T> : DynamicObject { public T ToStatic() { return this._value; } } In the above TryGetMember() method, please notice it does not output the member’s value, but output a wrapped member value (that is, memberValue.ToDynamic()). This is very important to make the reflection fluent. Now the code becomes: IEnumerable<Product> results = database.ToDynamic() // Here starts fluent reflection. .Provider.Execute(query.Expression).ReturnValue .ToStatic(); // Unwraps to get the static value. With the help of TryConvert(): public class DynamicWrapper<T> : DynamicObject { public override bool TryConvert(ConvertBinder binder, out object result) { result = this._value; return true; } } ToStatic() can be omitted: IEnumerable<Product> results = database.ToDynamic() .Provider.Execute(query.Expression).ReturnValue; // Automatically converts to expected static value. Take a look at the reflection code at the beginning of this post again. Now it is much much simplified! Special scenarios In 90% of the scenarios ToDynamic() is enough. But there are some special scenarios. Access static members Using extension method ToDynamic() for accessing static members does not make sense. Instead, DynamicWrapper<T> has a parameterless constructor to handle these scenarios: public class DynamicWrapper<T> : DynamicObject { public DynamicWrapper() // For static. { this._type = typeof(T); this._isValueType = this._type.IsValueType; } } The reflection code should be like this: dynamic wrapper = new DynamicWrapper<StaticClass>(); int value = wrapper._value; int result = wrapper.PrivateMethod(); So accessing static member is also simple, and fluent of course. Change instances of value types Value type is much more complex. The main problem is, value type is copied when passing to a method as a parameter. This is why ref keyword is used for the constructor. That is, if a value type instance is passed to DynamicWrapper<T>, the instance itself will be stored in this._value of DynamicWrapper<T>. Without the ref keyword, when this._value is changed, the value type instance itself does not change. Consider FieldInfo.SetValue(). In the value type scenarios, invoking FieldInfo.SetValue(this._value, value) does not change this._value, because it changes the copy of this._value. I searched the Web and found a solution for setting the value of field: internal static class FieldInfoExtensions { internal static void SetValue<T>(this FieldInfo field, ref T obj, object value) { if (typeof(T).IsValueType) { field.SetValueDirect(__makeref(obj), value); // For value type. } else { field.SetValue(obj, value); // For reference type. } } } Here __makeref is a undocumented keyword of C#. But method invocation has problem. This is the source code of TryInvokeMember(): public override bool TryInvokeMember(InvokeMemberBinder binder, object[] args, out object result) { if (binder == null) { throw new ArgumentNullException("binder"); } MethodInfo method = this._type.GetTypeMethod(binder.Name, args) ?? this._type.GetInterfaceMethod(binder.Name, args) ?? this._type.GetBaseMethod(binder.Name, args); if (method != null) { // Oops! // If the returnValue is a struct, it is copied to heap. object resultValue = method.Invoke(this._value, args); // And result is a wrapper of that copied struct. result = new DynamicWrapper<object>(ref resultValue); return true; } result = null; return false; } If the returned value is of value type, it will definitely copied, because MethodInfo.Invoke() does return object. If changing the value of the result, the copied struct is changed instead of the original struct. And so is the property and index accessing. They are both actually method invocation. For less confusion, setting property and index are not allowed on struct. Conclusions The DynamicWrapper<T> provides a simplified solution for reflection programming. It works for normal classes (reference types), accessing both instance and static members. In most of the scenarios, just remember to invoke ToDynamic() method, and access whatever you want: StaticType result = someValue.ToDynamic()._field.Method().Property[index]; In some special scenarios which requires changing the value of a struct (value type), this DynamicWrapper<T> does not work perfectly. Only changing struct’s field value is supported. The source code can be downloaded from here, including a few unit test code.

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  • With WebMatrix, How do I Connect to a MySQL Database on a Colleague's Machine?

    - by Ash Clarke
    I have scoured Google trying to discover how to do this, but essentially I want to connect to a colleague's MySQL database for working together on a Wordpress installation. I am having no luck and keep getting an error about the connection not being possible: Unable to connect to any of the specified MySQL hosts. MySql.Data.MySqlClient.MySqlException (0x80004005): Unable to connect to any of the specified MySQL hosts. at MySql.Data.MySqlClient.NativeDriver.Open() at MySql.Data.MySqlClient.Driver.Open() at MySql.Data.MySqlClient.Driver.Create(MySqlConnectionStringBuilder settings) at MySql.Data.MySqlClient.MySqlPool.GetPooledConnection() at MySql.Data.MySqlClient.MySqlPool.TryToGetDriver() at MySql.Data.MySqlClient.MySqlPool.GetConnection() at MySql.Data.MySqlClient.MySqlConnection.Open() at Microsoft.WebMatrix.DatabaseManager.MySqlDatabase.MySqlDatabaseProvider.TestConnection(String connectionString) at Microsoft.WebMatrix.DatabaseManager.IisDbManagerModuleService.TestConnection(DatabaseConnection databaseConnection, String configPathState) at Microsoft.WebMatrix.DatabaseManager.Client.ClientConnection.Test(ManagementConfigurationPath configPath) at Microsoft.WebMatrix.DatabaseManager.Client.DatabaseHierarchyInfo.EnsureLoaded() The connection details are copied from my colleague's connection string, with the exception of the server being modified to match the IP address of his machine. I'm not sure if there is a firewall port I have to open or a configuration file I have to modify, but I'm not having much luck so far. (There is a strong chance that, by default, web matrix / iis express doesn't set the mysql database it creates to accept remote connections. If anyone knows how to change this, that would be grand!) Anyone have any ideas?

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  • Coldfusion 9 losing connection to MySQL 5 database server a couple of weeks after the server is started

    - by user1503757
    We get the following Coldfusion error message after our server have been running for a couple of weeks: Error Executing Database Query.Could not create connection to database server. Attempted reconnect 3 times We run Coldfusion Enterprise 9 on a one year old XServer with Snow Leopard and MySQL 5 The server has about ten DSN set up in the Coldfusion Administrator All local, with default advanced settings, and host set to "localhost" The server is not under heavy load. The strange thing is that after a restart of the server, everything works fine. Then after a week or so, some databases will stop working, in the sense that Coldfusion cannot create a connection to them. If I then go to the Coldfusion Administrator and click "Verify all datasources", I will get that only 2 or 3 got verified, the other ones failed, and it is always the same datasources that can't be verified when the server starts to behave like this if I try to verify again, BUT NOT neccessary the same datasources that couldn't be verified the last time the server behaved like this. I know about the setting "max_connections" and we have included a line for that setting in the MySQL config file and set it to 2000, and when we read it by a query it says "2000", so that can't be the problem. Anyone?

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  • How to get just value from database query in Excel?

    - by Corin
    I'm creating a spreadsheet as a collection point of information from a number of MS Access databases. I will run a query on each database to get a count of records in a particular table. Each database has the same structure but different content as they are used in different situations. So the query returns a single value, rec_count. I've figured out how to create that query, save it and then use it as the data source. So far so good. The problem is that Excel treats the query results as a table. So instead of getting just the single value the query returns, I also get the field name. Thus the result takes up two cells instead of one. When linking in the data source, I only see Table, PivotTable Report and PivotChart as options for viewing the data. I don't want any of those. I just want the single value without any formatting, column headers, etc. Is there a way to do this is Excel 2007?

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  • Is Ubuntu a bad distro for a standalone mysql database server?

    - by DhruvPathak
    I read an article here : http://www.mysqlperformanceblog.com/2011/12/08/which-linux-distribution-for-mysql-server/ On the other end there are Debian and Ubuntu. Both use tool called dpkg for package management. There isn’t a month that I log in to a system based on either distribution where there are no issues with packages consistency. Unfinished installations, unresolved conflicts are so common that it’s just beyond simple negligence. The packaging system is just not robust enough. Another problem is that one broken package may block you from installing or uninstalling anything else. Imagine that someone left system in such shape, you prepared for downtime, stopped MySQL and… error – text editor has not been properly installed, so you cannot upgrade MySQL either until the problem is fixed. In a stressful situation when downtime clock ticks – annoying at best We prefer Ubuntu server because of familiarity and Ubuntu also being development environment. Questions: Is Ubuntu used commonly in production for a mysql database server ? Is it worth the trouble ever to have one distro eg Ubuntu in web server, and another say Red Hat in database server ? Or Is a homogenous server pool a better choice ?

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  • Oracle SQL Developer Data Modeler: What Tables Aren’t In At Least One SubView?

    - by thatjeffsmith
    Organizing your data model makes the information easier to consume. One of the organizational tools provided by Oracle SQL Developer Data Modeler is the ‘SubView.’ In a nutshell, a SubView is a subset of your model. The Challenge: I’ve just created a model which represents my entire ____________ application. We’ll call it ‘residential lending.’ Instead of having all 100+ tables in a single model diagram, I want to break out the tables by module, e.g. appraisals, credit reports, work histories, customers, etc. I’ve spent several hours breaking out the tables to one or more SubViews, but I think i may have missed a few. Is there an easy way to see what tables aren’t in at least ONE subview? The Answer Yes, mostly. The mostly comes about from the way I’m going to accomplish this task. It involves querying the SQL Developer Data Modeler Reporting Schema. So if you don’t have the Reporting Schema setup, you’ll need to do so. Got it? Good, let’s proceed. Before you start querying your Reporting Schema, you might need a data model for the actual reporting schema…meta-meta data! You could reverse engineer the data modeler reporting schema to a new data model, or you could just reference the PDFs in \datamodeler\reports\Reporting Schema diagrams directory. Here’s a hint, it’s THIS one The Query Well, it’s actually going to be at least 2 queries. We need to get a list of distinct designs stored in your repository. For giggles, I’m going to get a listing including each version of the model. So I can query based on design and version, or in this case, timestamp of when it was added to the repository. We’ll get that from the DMRS_DESIGNS table: SELECT DISTINCT design_name, design_ovid, date_published FROM DMRS_designs Then I’m going to feed the design_ovid, down to a subquery for my child report. select name, count(distinct diagram_id) from DMRS_DIAGRAM_ELEMENTS where design_ovid = :dESIGN_OVID and type = 'Table' group by name having count(distinct diagram_id) < 2 order by count(distinct diagram_id) desc Each diagram element has an entry in this table, so I need to filter on type=’Table.’ Each design has AT LEAST one diagram, the master diagram. So any relational table in this table, only having one listing means it’s not in any SubViews. If you have overloaded object names, which is VERY possible, you’ll want to do the report off of ‘OBJECT_ID’, but then you’ll need to correlate that to the NAME, as I doubt you’re so intimate with your designs that you recognize the GUIDs So I’m going to cheat and just stick with names, but I think you get the gist. My Model Of my almost 90 tables, how many of those have I not added to at least one SubView? Now let’s run my report! Voila! My ‘BEER2′ table isn’t in any SubView! It says ’1′ because the main model diagram counts as a view. So if the count came back as ’2′, that would mean the table was in the main model diagram and in 1 SubView diagram. And I know what you’re thinking, what kind of residential lending program would have a table called ‘BEER2?’ Let’s just say, that my business model has some kinks to work out!

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  • Using the ASP.NET Membership API with SQL Server / SQL Azure: The new &ldquo;System.Web.Providers&rdquo; namespace

    - by Harish Ranganathan
    The Membership API came in .NET 2.0 and was a huge enhancement in building web applications with users, managing roles, permissions etc.,  The Membership API by default uses SQL Express and until Visual Studio 2008, it was available only through the ASP.NET Configuration manager screen (Website – ASP.NET Configuration) or (Project – ASP.NET Configuration) and for every application, one has to manually visit this place to start using the Security and other settings.  Upon doing that the default SQL Express database aspnet.mdf is created to store all the user profiles. Starting Visual Studio 2010 and .NET 4.0, the Default Website template includes the Membership API controls as a part of the page i.e. When you create a “File – New – ASP.NET Web Application” or an “ASP.NET MVC Application”, by default the Login/Register controls are enabled in the MasterPage and they are termed under “ApplicationServices” setting in the web.config file with connection string pointed to the SQL Express database. In fact, when you run the default website and click on “Logon” –> “Register”, and enter the details for registration and click “Register”, that is the time the aspnet.mdf file is created with the tables for Users, Roles, UsersInRoles, Profile etc., Now, this uses the default SQL Express database within the App_Data folder.  If you want to move your Membership information to some other database such as SQL Server, SQL CE or SQL Azure, you need to manually run the aspnet_regsql command and specify the destination database name. This would create all the Tables, Procedures and Views required to handle the Membership information.  Thereafter you can change the connection string for “ApplicationServices” to point to the database where you had run all the scripts. Now, enter “System.Web.Providers” Alpha. This is available as a part of the NuGet package library.  Scott Hanselman has a neat post describing the steps required to get it up and running as well as doing the basic changes  at http://www.hanselman.com/blog/IntroducingSystemWebProvidersASPNETUniversalProvidersForSessionMembershipRolesAndUserProfileOnSQLCompactAndSQLAzure.aspx Pretty much, it covers what the new System.Web.Providers do. One thing I wanted to clarify is that, the new “System.Web.Providers” add a lot of new settings which are also marked as the defaults, in the web.config.  Even now, they use SQL Express as the default database.  But, if you change the connection string for “DefaultConnection” under connectionStrings to point to your SQL Server or SQL Azure, Membership API would now be able to create all the tables, procedures and views at the destination specified (i.e. SQL Server or SQL Azure). In my case, I modified the DefaultConneciton to point to my SQL Azure database.  Next, I hit F5 to run the application.  The default view loads.  I clicked on “LogOn” and then “Register” since I knew there are no tables/users as of then.  One thing to note is that, I had put “NewDB” as the database name in the connection string that points to SQL Azure.  NewDB wasn’t existing and I would assume it would be created before the tables/views/procedures for Membership are created. Once I clicked on the “Register” to register my first username, it took a while and then registered as well as logged in me in.  Also, I went to the SQL Azure Management Portal and verified that there exists “NewDB” which has just been created I could also connect to the SQL Azure database “NewDB” from Management Studio and found that the tables now don’t have the aspnet_ prefix.  The tables were simply Users, Roles, UsersInRoles, Profiles etc., So, with a few clicks and configuration change, I could actually set up the user base for my application on SQL Azure and even make the SessionState, Roles, Profiles being stored in SQL Azure database. The new System.Web.Proivders also required MARS (MultipleActiveResultSets=true) setting since it uses Entity Framework for the DAL operations.  Also, the “Project – ASP.NET Configuration” screen can be used to further create/manage users/roles etc., although the data is stored on the remote database. With that, a long pending request from the community to have the ability to configure and use remote databases for Application users management without having to run the scripts from SQL Express is fulfilled. Cheers !!!

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  • Essbase BSO Data Fragmentation

    - by Ann Donahue
    Essbase BSO Data Fragmentation Data fragmentation naturally occurs in Essbase Block Storage (BSO) databases where there are a lot of end user data updates, incremental data loads, many lock and send, and/or many calculations executed.  If an Essbase database starts to experience performance slow-downs, this is an indication that there may be too much fragmentation.  See Chapter 54 Improving Essbase Performance in the Essbase DBA Guide for more details on measuring and eliminating fragmentation: http://docs.oracle.com/cd/E17236_01/epm.1112/esb_dbag/daprcset.html Fragmentation is likely to occur in the following situations: Read/write databases that users are constantly updating data Databases that execute calculations around the clock Databases that frequently update and recalculate dense members Data loads that are poorly designed Databases that contain a significant number of Dynamic Calc and Store members Databases that use an isolation level of uncommitted access with commit block set to zero There are two types of data block fragmentation Free space tracking, which is measured using the Average Fragmentation Quotient statistic. Block order on disk, which is measured using the Average Cluster Ratio statistic. Average Fragmentation Quotient The Average Fragmentation Quotient ratio measures free space in a given database.  As you update and calculate data, empty spaces occur when a block can no longer fit in its original space and will either append at the end of the file or fit in another empty space that is large enough.  These empty spaces take up space in the .PAG files.  The higher the number the more empty spaces you have, therefore, the bigger the .PAG file and the longer it takes to traverse through the .PAG file to get to a particular record.  An Average Fragmentation Quotient value of 3.174765 means the database is 3% fragmented with free space. Average Cluster Ratio Average Cluster Ratio describes the order the blocks actually exist in the database. An Average Cluster Ratio number of 1 means all the blocks are ordered in the correct sequence in the order of the Outline.  As you load data and calculate data blocks, the sequence can start to be out of order.  This is because when you write to a block it may not be able to place back in the exact same spot in the database that it existed before.  The lower this number the more out of order it becomes and the more it affects performance.  An Average Cluster Ratio value of 1 means no fragmentation.  Any value lower than 1 i.e. 0.01032828 means the data blocks are getting further out of order from the outline order. Eliminating Data Block Fragmentation Both types of data block fragmentation can be removed by doing a dense restructure or export/clear/import of the data.  There are two types of dense restructure: 1. Implicit Restructures Implicit dense restructure happens when outline changes are done using EAS Outline Editor or Dimension Build. Essbase restructures create new .PAG files restructuring the data blocks in the .PAG files. When Essbase restructures the data blocks, it regenerates the index automatically so that index entries point to the new data blocks. Empty blocks are NOT removed with implicit restructures. 2. Explicit Restructures Explicit dense restructure happens when a manual initiation of the database restructure is executed. An explicit dense restructure is a full restructure which comprises of a dense restructure as outlined above plus the removal of empty blocks Empty Blocks vs. Fragmentation The existence of empty blocks is not considered fragmentation.  Empty blocks can be created through calc scripts or formulas.  An empty block will add to an existing database block count and will be included in the block counts of the database properties.  There are no statistics for empty blocks.  The only way to determine if empty blocks exist in an Essbase database is to record your current block count, export the entire database, clear the database then import the exported data.  If the block count decreased, the difference is the number of empty blocks that had existed in the database.

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  • RHEL - blocked FC remote port time out: saving binding

    - by Dev G
    My Server went into a faulty state since the database could not write on the partition. I found out that the partition went into Read Only mode. Finally to fix it, I had to do a hard reboot. Linux 2.6.18-164.el5PAE #1 SMP Tue Aug 18 15:59:11 EDT 2009 i686 i686 i386 GNU/Linux /var/log/messages Oct 31 00:56:45 ota3g1 Had[17275]: VCS ERROR V-16-1-10214 Concurrency Violation:CurrentCount increased above 1 for failover group sg_network Oct 31 00:57:05 ota3g1 Had[17275]: VCS CRITICAL V-16-1-50086 CPU usage on ota3g1.mtsallstream.com is 100% Oct 31 01:01:47 ota3g1 Had[17275]: VCS ERROR V-16-1-10214 Concurrency Violation:CurrentCount increased above 1 for failover group sg_network Oct 31 01:06:50 ota3g1 Had[17275]: VCS ERROR V-16-1-10214 Concurrency Violation:CurrentCount increased above 1 for failover group sg_network Oct 31 01:11:52 ota3g1 Had[17275]: VCS ERROR V-16-1-10214 Concurrency Violation:CurrentCount increased above 1 for failover group sg_network Oct 31 01:12:10 ota3g1 kernel: lpfc 0000:29:00.1: 1:1305 Link Down Event x2 received Data: x2 x20 x80000 x0 x0 Oct 31 01:12:10 ota3g1 kernel: lpfc 0000:29:00.1: 1:1303 Link Up Event x3 received Data: x3 x1 x10 x1 x0 x0 0 Oct 31 01:12:12 ota3g1 kernel: lpfc 0000:29:00.1: 1:1305 Link Down Event x4 received Data: x4 x20 x80000 x0 x0 Oct 31 01:12:40 ota3g1 kernel: rport-8:0-0: blocked FC remote port time out: saving binding Oct 31 01:12:40 ota3g1 kernel: lpfc 0000:29:00.1: 1:(0):0203 Devloss timeout on WWPN 20:25:00:a0:b8:74:f5:65 NPort x0000e4 Data: x0 x7 x0 Oct 31 01:12:40 ota3g1 kernel: sd 8:0:0:4: SCSI error: return code = 0x00010000 Oct 31 01:12:40 ota3g1 kernel: end_request: I/O error, dev sdi, sector 38617577 Oct 31 01:12:40 ota3g1 kernel: sd 8:0:0:4: SCSI error: return code = 0x00010000 Oct 31 01:12:40 ota3g1 kernel: end_request: I/O error, dev sdi, sector 283532153 Oct 31 01:12:40 ota3g1 kernel: sd 8:0:0:4: SCSI error: return code = 0x00010000 Oct 31 01:12:40 ota3g1 kernel: end_request: I/O error, dev sdi, sector 90825 Oct 31 01:12:40 ota3g1 kernel: Aborting journal on device dm-16. Oct 31 01:12:40 ota3g1 kernel: sd 8:0:0:4: SCSI error: return code = 0x00010000 Oct 31 01:12:40 ota3g1 kernel: end_request: I/O error, dev sdi, sector 868841 Oct 31 01:12:40 ota3g1 kernel: sd 8:0:0:4: SCSI error: return code = 0x00010000 Oct 31 01:12:40 ota3g1 kernel: Aborting journal on device dm-10. Oct 31 01:12:40 ota3g1 kernel: end_request: I/O error, dev sdi, sector 37759889 Oct 31 01:12:40 ota3g1 kernel: sd 8:0:0:4: SCSI error: return code = 0x00010000 Oct 31 01:12:40 ota3g1 kernel: end_request: I/O error, dev sdi, sector 283349449 Oct 31 01:12:40 ota3g1 kernel: printk: 6 messages suppressed. Oct 31 01:12:40 ota3g1 kernel: Aborting journal on device dm-12. Oct 31 01:12:40 ota3g1 kernel: EXT3-fs error (device dm-12) in ext3_reserve_inode_write: Journal has aborted Oct 31 01:12:40 ota3g1 kernel: Buffer I/O error on device dm-16, logical block 1545 Oct 31 01:12:40 ota3g1 kernel: lost page write due to I/O error on dm-16 Oct 31 01:12:40 ota3g1 kernel: sd 8:0:0:4: SCSI error: return code = 0x00010000 Oct 31 01:12:40 ota3g1 kernel: end_request: I/O error, dev sdi, sector 12745 Oct 31 01:12:40 ota3g1 kernel: Buffer I/O error on device dm-10, logical block 1545 Oct 31 01:12:40 ota3g1 kernel: EXT3-fs error (device dm-16) in ext3_reserve_inode_write: Journal has aborted Oct 31 01:12:40 ota3g1 kernel: lost page write due to I/O error on dm-10 Oct 31 01:12:40 ota3g1 kernel: sd 8:0:0:4: SCSI error: return code = 0x00010000 Oct 31 01:12:40 ota3g1 kernel: end_request: I/O error, dev sdi, sector 37749121 Oct 31 01:12:40 ota3g1 kernel: Buffer I/O error on device dm-12, logical block 0 Oct 31 01:12:40 ota3g1 kernel: lost page write due to I/O error on dm-12 Oct 31 01:12:40 ota3g1 kernel: sd 8:0:0:4: SCSI error: return code = 0x00010000 Oct 31 01:12:40 ota3g1 kernel: EXT3-fs error (device dm-12) in ext3_dirty_inode: Journal has aborted Oct 31 01:12:40 ota3g1 kernel: end_request: I/O error, dev sdi, sector 37757897 Oct 31 01:12:40 ota3g1 kernel: Buffer I/O error on device dm-12, logical block 1097 Oct 31 01:12:40 ota3g1 kernel: lost page write due to I/O error on dm-12 Oct 31 01:12:40 ota3g1 kernel: sd 8:0:0:4: SCSI error: return code = 0x00010000 Oct 31 01:12:40 ota3g1 kernel: end_request: I/O error, dev sdi, sector 283337089 Oct 31 01:12:40 ota3g1 kernel: Buffer I/O error on device dm-16, logical block 0 Oct 31 01:12:40 ota3g1 kernel: lost page write due to I/O error on dm-16 Oct 31 01:12:40 ota3g1 kernel: sd 8:0:0:4: SCSI error: return code = 0x00010000 Oct 31 01:12:40 ota3g1 kernel: EXT3-fs error (device dm-16) in ext3_dirty_inode: Journal has aborted Oct 31 01:12:40 ota3g1 kernel: end_request: I/O error, dev sdi, sector 37749121 Oct 31 01:12:40 ota3g1 kernel: Buffer I/O error on device dm-12, logical block 0 Oct 31 01:12:41 ota3g1 kernel: lost page write due to I/O error on dm-12 Oct 31 01:12:41 ota3g1 kernel: sd 8:0:0:4: SCSI error: return code = 0x00010000 Oct 31 01:12:41 ota3g1 kernel: end_request: I/O error, dev sdi, sector 283337089 Oct 31 01:12:41 ota3g1 kernel: Buffer I/O error on device dm-16, logical block 0 Oct 31 01:12:41 ota3g1 kernel: lost page write due to I/O error on dm-16 Oct 31 01:12:41 ota3g1 kernel: sd 8:0:0:4: SCSI error: return code = 0x00010000 df -h Filesystem Size Used Avail Use% Mounted on /dev/mapper/cciss-root 4.9G 730M 3.9G 16% / /dev/mapper/cciss-home 9.7G 1.2G 8.1G 13% /home /dev/mapper/cciss-var 9.7G 494M 8.8G 6% /var /dev/mapper/cciss-usr 15G 2.6G 12G 19% /usr /dev/mapper/cciss-tmp 3.9G 153M 3.6G 5% /tmp /dev/sda1 996M 43M 902M 5% /boot tmpfs 5.9G 0 5.9G 0% /dev/shm /dev/mapper/cciss-product 25G 16G 7.4G 68% /product /dev/mapper/cciss-opt 20G 4.5G 14G 25% /opt /dev/mapper/dg_db1-vol_db1_system 18G 2.2G 15G 14% /database/OTADB/sys /dev/mapper/dg_db1-vol_db1_undo 18G 5.8G 12G 35% /database/OTADB/undo /dev/mapper/dg_db1-vol_db1_redo 8.9G 4.3G 4.2G 51% /database/OTADB/redo /dev/mapper/dg_db1-vol_db1_sgbd 8.9G 654M 7.8G 8% /database/OTADB/admin /dev/mapper/dg_db1-vol_db1_arch 98G 24G 69G 26% /database/OTADB/arch /dev/mapper/dg_db1-vol_db1_indexes 240G 14G 214G 6% /database/OTADB/index /dev/mapper/dg_db1-vol_db1_data 275G 47G 215G 18% /database/OTADB/data /dev/mapper/dg_dbrman-vol_db_rman 8.9G 351M 8.1G 5% /database/RMAN /dev/mapper/dg_app1-vol_app1 151G 113G 31G 79% /files/ota /etc/fstab /dev/cciss/root / ext3 defaults 1 1 /dev/cciss/home /home ext3 defaults 1 2 /dev/cciss/var /var ext3 defaults 1 2 /dev/cciss/usr /usr ext3 defaults 1 2 /dev/cciss/tmp /tmp ext3 defaults 1 2 LABEL=/boot /boot ext3 defaults 1 2 tmpfs /dev/shm tmpfs defaults 0 0 devpts /dev/pts devpts gid=5,mode=620 0 0 sysfs /sys sysfs defaults 0 0 proc /proc proc defaults 0 0 /dev/cciss/swap swap swap defaults 0 0 /dev/cciss/product /product ext3 defaults 1 2 /dev/cciss/opt /opt ext3 defaults 1 2 /dev/dg_db1/vol_db1_system /database/OTADB/sys ext3 defaults 1 2 /dev/dg_db1/vol_db1_undo /database/OTADB/undo ext3 defaults 1 2 /dev/dg_db1/vol_db1_redo /database/OTADB/redo ext3 defaults 1 2 /dev/dg_db1/vol_db1_sgbd /database/OTADB/admin ext3 defaults 1 2 /dev/dg_db1/vol_db1_arch /database/OTADB/arch ext3 defaults 1 2 /dev/dg_db1/vol_db1_indexes /database/OTADB/index ext3 defaults 1 2 /dev/dg_db1/vol_db1_data /database/OTADB/data ext3 defaults 1 2 /dev/dg_dbrman/vol_db_rman /database/RMAN ext3 defaults 1 2 /dev/dg_app1/vol_app1 /files/ota ext3 defaults 1 2 Thanks for all the help.

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  • Node.js Adventure - When Node Flying in Wind

    - by Shaun
    In the first post of this series I mentioned some popular modules in the community, such as underscore, async, etc.. I also listed a module named “Wind (zh-CN)”, which is created by one of my friend, Jeff Zhao (zh-CN). Now I would like to use a separated post to introduce this module since I feel it brings a new async programming style in not only Node.js but JavaScript world. If you know or heard about the new feature in C# 5.0 called “async and await”, or you learnt F#, you will find the “Wind” brings the similar async programming experience in JavaScript. By using “Wind”, we can write async code that looks like the sync code. The callbacks, async stats and exceptions will be handled by “Wind” automatically and transparently.   What’s the Problem: Dense “Callback” Phobia Let’s firstly back to my second post in this series. As I mentioned in that post, when we wanted to read some records from SQL Server we need to open the database connection, and then execute the query. In Node.js all IO operation are designed as async callback pattern which means when the operation was done, it will invoke a function which was taken from the last parameter. For example the database connection opening code would be like this. 1: sql.open(connectionString, function(error, conn) { 2: if(error) { 3: // some error handling code 4: } 5: else { 6: // connection opened successfully 7: } 8: }); And then if we need to query the database the code would be like this. It nested in the previous function. 1: sql.open(connectionString, function(error, conn) { 2: if(error) { 3: // some error handling code 4: } 5: else { 6: // connection opened successfully 7: conn.queryRaw(command, function(error, results) { 8: if(error) { 9: // failed to execute this command 10: } 11: else { 12: // records retrieved successfully 13: } 14: }; 15: } 16: }); Assuming if we need to copy some data from this database to another then we need to open another connection and execute the command within the function under the query function. 1: sql.open(connectionString, function(error, conn) { 2: if(error) { 3: // some error handling code 4: } 5: else { 6: // connection opened successfully 7: conn.queryRaw(command, function(error, results) { 8: if(error) { 9: // failed to execute this command 10: } 11: else { 12: // records retrieved successfully 13: target.open(targetConnectionString, function(error, t_conn) { 14: if(error) { 15: // connect failed 16: } 17: else { 18: t_conn.queryRaw(copy_command, function(error, results) { 19: if(error) { 20: // copy failed 21: } 22: else { 23: // and then, what do you want to do now... 24: } 25: }; 26: } 27: }; 28: } 29: }; 30: } 31: }); This is just an example. In the real project the logic would be more complicated. This means our application might be messed up and the business process will be fragged by many callback functions. I would like call this “Dense Callback Phobia”. This might be a challenge how to make code straightforward and easy to read, something like below. 1: try 2: { 3: // open source connection 4: var s_conn = sqlConnect(s_connectionString); 5: // retrieve data 6: var results = sqlExecuteCommand(s_conn, s_command); 7: 8: // open target connection 9: var t_conn = sqlConnect(t_connectionString); 10: // prepare the copy command 11: var t_command = getCopyCommand(results); 12: // execute the copy command 13: sqlExecuteCommand(s_conn, t_command); 14: } 15: catch (ex) 16: { 17: // error handling 18: }   What’s the Problem: Sync-styled Async Programming Similar as the previous problem, the callback-styled async programming model makes the upcoming operation as a part of the current operation, and mixed with the error handling code. So it’s very hard to understand what on earth this code will do. And since Node.js utilizes non-blocking IO mode, we cannot invoke those operations one by one, as they will be executed concurrently. For example, in this post when I tried to copy the records from Windows Azure SQL Database (a.k.a. WASD) to Windows Azure Table Storage, if I just insert the data into table storage one by one and then print the “Finished” message, I will see the message shown before the data had been copied. This is because all operations were executed at the same time. In order to make the copy operation and print operation executed synchronously I introduced a module named “async” and the code was changed as below. 1: async.forEach(results.rows, 2: function (row, callback) { 3: var resource = { 4: "PartitionKey": row[1], 5: "RowKey": row[0], 6: "Value": row[2] 7: }; 8: client.insertEntity(tableName, resource, function (error) { 9: if (error) { 10: callback(error); 11: } 12: else { 13: console.log("entity inserted."); 14: callback(null); 15: } 16: }); 17: }, 18: function (error) { 19: if (error) { 20: error["target"] = "insertEntity"; 21: res.send(500, error); 22: } 23: else { 24: console.log("all done."); 25: res.send(200, "Done!"); 26: } 27: }); It ensured that the “Finished” message will be printed when all table entities had been inserted. But it cannot promise that the records will be inserted in sequence. It might be another challenge to make the code looks like in sync-style? 1: try 2: { 3: forEach(row in rows) { 4: var entity = { /* ... */ }; 5: tableClient.insert(tableName, entity); 6: } 7:  8: console.log("Finished"); 9: } 10: catch (ex) { 11: console.log(ex); 12: }   How “Wind” Helps “Wind” is a JavaScript library which provides the control flow with plain JavaScript for asynchronous programming (and more) without additional pre-compiling steps. It’s available in NPM so that we can install it through “npm install wind”. Now let’s create a very simple Node.js application as the example. This application will take some website URLs from the command arguments and tried to retrieve the body length and print them in console. Then at the end print “Finish”. I’m going to use “request” module to make the HTTP call simple so I also need to install by the command “npm install request”. The code would be like this. 1: var request = require("request"); 2:  3: // get the urls from arguments, the first two arguments are `node.exe` and `fetch.js` 4: var args = process.argv.splice(2); 5:  6: // main function 7: var main = function() { 8: for(var i = 0; i < args.length; i++) { 9: // get the url 10: var url = args[i]; 11: // send the http request and try to get the response and body 12: request(url, function(error, response, body) { 13: if(!error && response.statusCode == 200) { 14: // log the url and the body length 15: console.log( 16: "%s: %d.", 17: response.request.uri.href, 18: body.length); 19: } 20: else { 21: // log error 22: console.log(error); 23: } 24: }); 25: } 26: 27: // finished 28: console.log("Finished"); 29: }; 30:  31: // execute the main function 32: main(); Let’s execute this application. (I made them in multi-lines for better reading.) 1: node fetch.js 2: "http://www.igt.com/us-en.aspx" 3: "http://www.igt.com/us-en/games.aspx" 4: "http://www.igt.com/us-en/cabinets.aspx" 5: "http://www.igt.com/us-en/systems.aspx" 6: "http://www.igt.com/us-en/interactive.aspx" 7: "http://www.igt.com/us-en/social-gaming.aspx" 8: "http://www.igt.com/support.aspx" Below is the output. As you can see the finish message was printed at the beginning, and the pages’ length retrieved in a different order than we specified. This is because in this code the request command, console logging command are executed asynchronously and concurrently. Now let’s introduce “Wind” to make them executed in order, which means it will request the websites one by one, and print the message at the end.   First of all we need to import the “Wind” package and make sure the there’s only one global variant named “Wind”, and ensure it’s “Wind” instead of “wind”. 1: var Wind = require("wind");   Next, we need to tell “Wind” which code will be executed asynchronously so that “Wind” can control the execution process. In this case the “request” operation executed asynchronously so we will create a “Task” by using a build-in helps function in “Wind” named Wind.Async.Task.create. 1: var requestBodyLengthAsync = function(url) { 2: return Wind.Async.Task.create(function(t) { 3: request(url, function(error, response, body) { 4: if(error || response.statusCode != 200) { 5: t.complete("failure", error); 6: } 7: else { 8: var data = 9: { 10: uri: response.request.uri.href, 11: length: body.length 12: }; 13: t.complete("success", data); 14: } 15: }); 16: }); 17: }; The code above created a “Task” from the original request calling code. In “Wind” a “Task” means an operation will be finished in some time in the future. A “Task” can be started by invoke its start() method, but no one knows when it actually will be finished. The Wind.Async.Task.create helped us to create a task. The only parameter is a function where we can put the actual operation in, and then notify the task object it’s finished successfully or failed by using the complete() method. In the code above I invoked the request method. If it retrieved the response successfully I set the status of this task as “success” with the URL and body length. If it failed I set this task as “failure” and pass the error out.   Next, we will change the main() function. In “Wind” if we want a function can be controlled by Wind we need to mark it as “async”. This should be done by using the code below. 1: var main = eval(Wind.compile("async", function() { 2: })); When the application is running, Wind will detect “eval(Wind.compile(“async”, function” and generate an anonymous code from the body of this original function. Then the application will run the anonymous code instead of the original one. In our example the main function will be like this. 1: var main = eval(Wind.compile("async", function() { 2: for(var i = 0; i < args.length; i++) { 3: try 4: { 5: var result = $await(requestBodyLengthAsync(args[i])); 6: console.log( 7: "%s: %d.", 8: result.uri, 9: result.length); 10: } 11: catch (ex) { 12: console.log(ex); 13: } 14: } 15: 16: console.log("Finished"); 17: })); As you can see, when I tried to request the URL I use a new command named “$await”. It tells Wind, the operation next to $await will be executed asynchronously, and the main thread should be paused until it finished (or failed). So in this case, my application will be pause when the first response was received, and then print its body length, then try the next one. At the end, print the finish message.   Finally, execute the main function. The full code would be like this. 1: var request = require("request"); 2: var Wind = require("wind"); 3:  4: var args = process.argv.splice(2); 5:  6: var requestBodyLengthAsync = function(url) { 7: return Wind.Async.Task.create(function(t) { 8: request(url, function(error, response, body) { 9: if(error || response.statusCode != 200) { 10: t.complete("failure", error); 11: } 12: else { 13: var data = 14: { 15: uri: response.request.uri.href, 16: length: body.length 17: }; 18: t.complete("success", data); 19: } 20: }); 21: }); 22: }; 23:  24: var main = eval(Wind.compile("async", function() { 25: for(var i = 0; i < args.length; i++) { 26: try 27: { 28: var result = $await(requestBodyLengthAsync(args[i])); 29: console.log( 30: "%s: %d.", 31: result.uri, 32: result.length); 33: } 34: catch (ex) { 35: console.log(ex); 36: } 37: } 38: 39: console.log("Finished"); 40: })); 41:  42: main().start();   Run our new application. At the beginning we will see the compiled and generated code by Wind. Then we can see the pages were requested one by one, and at the end the finish message was printed. Below is the code Wind generated for us. As you can see the original code, the output code were shown. 1: // Original: 2: function () { 3: for(var i = 0; i < args.length; i++) { 4: try 5: { 6: var result = $await(requestBodyLengthAsync(args[i])); 7: console.log( 8: "%s: %d.", 9: result.uri, 10: result.length); 11: } 12: catch (ex) { 13: console.log(ex); 14: } 15: } 16: 17: console.log("Finished"); 18: } 19:  20: // Compiled: 21: /* async << function () { */ (function () { 22: var _builder_$0 = Wind.builders["async"]; 23: return _builder_$0.Start(this, 24: _builder_$0.Combine( 25: _builder_$0.Delay(function () { 26: /* var i = 0; */ var i = 0; 27: /* for ( */ return _builder_$0.For(function () { 28: /* ; i < args.length */ return i < args.length; 29: }, function () { 30: /* ; i ++) { */ i ++; 31: }, 32: /* try { */ _builder_$0.Try( 33: _builder_$0.Delay(function () { 34: /* var result = $await(requestBodyLengthAsync(args[i])); */ return _builder_$0.Bind(requestBodyLengthAsync(args[i]), function (result) { 35: /* console.log("%s: %d.", result.uri, result.length); */ console.log("%s: %d.", result.uri, result.length); 36: return _builder_$0.Normal(); 37: }); 38: }), 39: /* } catch (ex) { */ function (ex) { 40: /* console.log(ex); */ console.log(ex); 41: return _builder_$0.Normal(); 42: /* } */ }, 43: null 44: ) 45: /* } */ ); 46: }), 47: _builder_$0.Delay(function () { 48: /* console.log("Finished"); */ console.log("Finished"); 49: return _builder_$0.Normal(); 50: }) 51: ) 52: ); 53: /* } */ })   How Wind Works Someone may raise a big concern when you find I utilized “eval” in my code. Someone may assume that Wind utilizes “eval” to execute some code dynamically while “eval” is very low performance. But I would say, Wind does NOT use “eval” to run the code. It only use “eval” as a flag to know which code should be compiled at runtime. When the code was firstly been executed, Wind will check and find “eval(Wind.compile(“async”, function”. So that it knows this function should be compiled. Then it utilized parse-js to analyze the inner JavaScript and generated the anonymous code in memory. Then it rewrite the original code so that when the application was running it will use the anonymous one instead of the original one. Since the code generation was done at the beginning of the application was started, in the future no matter how long our application runs and how many times the async function was invoked, it will use the generated code, no need to generate again. So there’s no significant performance hurt when using Wind.   Wind in My Previous Demo Let’s adopt Wind into one of my previous demonstration and to see how it helps us to make our code simple, straightforward and easy to read and understand. In this post when I implemented the functionality that copied the records from my WASD to table storage, the logic would be like this. 1, Open database connection. 2, Execute a query to select all records from the table. 3, Recreate the table in Windows Azure table storage. 4, Create entities from each of the records retrieved previously, and then insert them into table storage. 5, Finally, show message as the HTTP response. But as the image below, since there are so many callbacks and async operations, it’s very hard to understand my logic from the code. Now let’s use Wind to rewrite our code. First of all, of course, we need the Wind package. Then we need to include the package files into project and mark them as “Copy always”. Add the Wind package into the source code. Pay attention to the variant name, you must use “Wind” instead of “wind”. 1: var express = require("express"); 2: var async = require("async"); 3: var sql = require("node-sqlserver"); 4: var azure = require("azure"); 5: var Wind = require("wind"); Now we need to create some async functions by using Wind. All async functions should be wrapped so that it can be controlled by Wind which are open database, retrieve records, recreate table (delete and create) and insert entity in table. Below are these new functions. All of them are created by using Wind.Async.Task.create. 1: sql.openAsync = function (connectionString) { 2: return Wind.Async.Task.create(function (t) { 3: sql.open(connectionString, function (error, conn) { 4: if (error) { 5: t.complete("failure", error); 6: } 7: else { 8: t.complete("success", conn); 9: } 10: }); 11: }); 12: }; 13:  14: sql.queryAsync = function (conn, query) { 15: return Wind.Async.Task.create(function (t) { 16: conn.queryRaw(query, function (error, results) { 17: if (error) { 18: t.complete("failure", error); 19: } 20: else { 21: t.complete("success", results); 22: } 23: }); 24: }); 25: }; 26:  27: azure.recreateTableAsync = function (tableName) { 28: return Wind.Async.Task.create(function (t) { 29: client.deleteTable(tableName, function (error, successful, response) { 30: console.log("delete table finished"); 31: client.createTableIfNotExists(tableName, function (error, successful, response) { 32: console.log("create table finished"); 33: if (error) { 34: t.complete("failure", error); 35: } 36: else { 37: t.complete("success", null); 38: } 39: }); 40: }); 41: }); 42: }; 43:  44: azure.insertEntityAsync = function (tableName, entity) { 45: return Wind.Async.Task.create(function (t) { 46: client.insertEntity(tableName, entity, function (error, entity, response) { 47: if (error) { 48: t.complete("failure", error); 49: } 50: else { 51: t.complete("success", null); 52: } 53: }); 54: }); 55: }; Then in order to use these functions we will create a new function which contains all steps for data copying. 1: var copyRecords = eval(Wind.compile("async", function (req, res) { 2: try { 3: } 4: catch (ex) { 5: console.log(ex); 6: res.send(500, "Internal error."); 7: } 8: })); Let’s execute steps one by one with the “$await” keyword introduced by Wind so that it will be invoked in sequence. First is to open the database connection. 1: var copyRecords = eval(Wind.compile("async", function (req, res) { 2: try { 3: // connect to the windows azure sql database 4: var conn = $await(sql.openAsync(connectionString)); 5: console.log("connection opened"); 6: } 7: catch (ex) { 8: console.log(ex); 9: res.send(500, "Internal error."); 10: } 11: })); Then retrieve all records from the database connection. 1: var copyRecords = eval(Wind.compile("async", function (req, res) { 2: try { 3: // connect to the windows azure sql database 4: var conn = $await(sql.openAsync(connectionString)); 5: console.log("connection opened"); 6: // retrieve all records from database 7: var results = $await(sql.queryAsync(conn, "SELECT * FROM [Resource]")); 8: console.log("records selected. count = %d", results.rows.length); 9: } 10: catch (ex) { 11: console.log(ex); 12: res.send(500, "Internal error."); 13: } 14: })); After recreated the table, we need to create the entities and insert them into table storage. 1: var copyRecords = eval(Wind.compile("async", function (req, res) { 2: try { 3: // connect to the windows azure sql database 4: var conn = $await(sql.openAsync(connectionString)); 5: console.log("connection opened"); 6: // retrieve all records from database 7: var results = $await(sql.queryAsync(conn, "SELECT * FROM [Resource]")); 8: console.log("records selected. count = %d", results.rows.length); 9: if (results.rows.length > 0) { 10: // recreate the table 11: $await(azure.recreateTableAsync(tableName)); 12: console.log("table created"); 13: // insert records in table storage one by one 14: for (var i = 0; i < results.rows.length; i++) { 15: var entity = { 16: "PartitionKey": results.rows[i][1], 17: "RowKey": results.rows[i][0], 18: "Value": results.rows[i][2] 19: }; 20: $await(azure.insertEntityAsync(tableName, entity)); 21: console.log("entity inserted"); 22: } 23: } 24: } 25: catch (ex) { 26: console.log(ex); 27: res.send(500, "Internal error."); 28: } 29: })); Finally, send response back to the browser. 1: var copyRecords = eval(Wind.compile("async", function (req, res) { 2: try { 3: // connect to the windows azure sql database 4: var conn = $await(sql.openAsync(connectionString)); 5: console.log("connection opened"); 6: // retrieve all records from database 7: var results = $await(sql.queryAsync(conn, "SELECT * FROM [Resource]")); 8: console.log("records selected. count = %d", results.rows.length); 9: if (results.rows.length > 0) { 10: // recreate the table 11: $await(azure.recreateTableAsync(tableName)); 12: console.log("table created"); 13: // insert records in table storage one by one 14: for (var i = 0; i < results.rows.length; i++) { 15: var entity = { 16: "PartitionKey": results.rows[i][1], 17: "RowKey": results.rows[i][0], 18: "Value": results.rows[i][2] 19: }; 20: $await(azure.insertEntityAsync(tableName, entity)); 21: console.log("entity inserted"); 22: } 23: // send response 24: console.log("all done"); 25: res.send(200, "All done!"); 26: } 27: } 28: catch (ex) { 29: console.log(ex); 30: res.send(500, "Internal error."); 31: } 32: })); If we compared with the previous code we will find now it became more readable and much easy to understand. It’s very easy to know what this function does even though without any comments. When user go to URL “/was/copyRecords” we will execute the function above. The code would be like this. 1: app.get("/was/copyRecords", function (req, res) { 2: copyRecords(req, res).start(); 3: }); And below is the logs printed in local compute emulator console. As we can see the functions executed one by one and then finally the response back to me browser.   Scaffold Functions in Wind Wind provides not only the async flow control and compile functions, but many scaffold methods as well. We can build our async code more easily by using them. I’m going to introduce some basic scaffold functions here. In the code above I created some functions which wrapped from the original async function such as open database, create table, etc.. All of them are very similar, created a task by using Wind.Async.Task.create, return error or result object through Task.complete function. In fact, Wind provides some functions for us to create task object from the original async functions. If the original async function only has a callback parameter, we can use Wind.Async.Binding.fromCallback method to get the task object directly. For example the code below returned the task object which wrapped the file exist check function. 1: var Wind = require("wind"); 2: var fs = require("fs"); 3:  4: fs.existsAsync = Wind.Async.Binding.fromCallback(fs.exists); In Node.js a very popular async function pattern is that, the first parameter in the callback function represent the error object, and the other parameters is the return values. In this case we can use another build-in function in Wind named Wind.Async.Binding.fromStandard. For example, the open database function can be created from the code below. 1: sql.openAsync = Wind.Async.Binding.fromStandard(sql.open); 2:  3: /* 4: sql.openAsync = function (connectionString) { 5: return Wind.Async.Task.create(function (t) { 6: sql.open(connectionString, function (error, conn) { 7: if (error) { 8: t.complete("failure", error); 9: } 10: else { 11: t.complete("success", conn); 12: } 13: }); 14: }); 15: }; 16: */ When I was testing the scaffold functions under Wind.Async.Binding I found for some functions, such as the Azure SDK insert entity function, cannot be processed correctly. So I personally suggest writing the wrapped method manually.   Another scaffold method in Wind is the parallel tasks coordination. In this example, the steps of open database, retrieve records and recreated table should be invoked one by one, but it can be executed in parallel when copying data from database to table storage. In Wind there’s a scaffold function named Task.whenAll which can be used here. Task.whenAll accepts a list of tasks and creates a new task. It will be returned only when all tasks had been completed, or any errors occurred. For example in the code below I used the Task.whenAll to make all copy operation executed at the same time. 1: var copyRecordsInParallel = eval(Wind.compile("async", function (req, res) { 2: try { 3: // connect to the windows azure sql database 4: var conn = $await(sql.openAsync(connectionString)); 5: console.log("connection opened"); 6: // retrieve all records from database 7: var results = $await(sql.queryAsync(conn, "SELECT * FROM [Resource]")); 8: console.log("records selected. count = %d", results.rows.length); 9: if (results.rows.length > 0) { 10: // recreate the table 11: $await(azure.recreateTableAsync(tableName)); 12: console.log("table created"); 13: // insert records in table storage in parallal 14: var tasks = new Array(results.rows.length); 15: for (var i = 0; i < results.rows.length; i++) { 16: var entity = { 17: "PartitionKey": results.rows[i][1], 18: "RowKey": results.rows[i][0], 19: "Value": results.rows[i][2] 20: }; 21: tasks[i] = azure.insertEntityAsync(tableName, entity); 22: } 23: $await(Wind.Async.Task.whenAll(tasks)); 24: // send response 25: console.log("all done"); 26: res.send(200, "All done!"); 27: } 28: } 29: catch (ex) { 30: console.log(ex); 31: res.send(500, "Internal error."); 32: } 33: })); 34:  35: app.get("/was/copyRecordsInParallel", function (req, res) { 36: copyRecordsInParallel(req, res).start(); 37: });   Besides the task creation and coordination, Wind supports the cancellation solution so that we can send the cancellation signal to the tasks. It also includes exception solution which means any exceptions will be reported to the caller function.   Summary In this post I introduced a Node.js module named Wind, which created by my friend Jeff Zhao. As you can see, different from other async library and framework, adopted the idea from F# and C#, Wind utilizes runtime code generation technology to make it more easily to write async, callback-based functions in a sync-style way. By using Wind there will be almost no callback, and the code will be very easy to understand. Currently Wind is still under developed and improved. There might be some problems but the author, Jeff, should be very happy and enthusiastic to learn your problems, feedback, suggestion and comments. You can contact Jeff by - Email: [email protected] - Group: https://groups.google.com/d/forum/windjs - GitHub: https://github.com/JeffreyZhao/wind/issues   Source code can be download here.   Hope this helps, Shaun All documents and related graphics, codes are provided "AS IS" without warranty of any kind. Copyright © Shaun Ziyan Xu. This work is licensed under the Creative Commons License.

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