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• Partitioning requests in code among several servers

  - by Jacques René Mesrine

  I have several forum servers (what they are is irrelevant) which stores posts from users and I want to be able to partition requests among these servers. I'm currently leaning towards partitioning them by geographic location. To improve the locality of data, users will be separated into regions e.g. North America, South America and so on. Is there any design pattern on how to implement the function that maps the partioning property to the server, so that this piece of code has high availability and would not become a single point of failure ? f( Region ) -> Server IP

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• Search filenames in MySQL database table restricted by filetype?

  - by ju

  Hello I have a MySQL database that I replicate from another server. The database contains a table with this columns ID, FileName and FileSize In the table there are more than 4'000'000 records. I want to make fast a search in FileName (varchar) column I found that I can use for this Sphinx search engine. The problem is that I want to restrict searches by filetype. Do I have to and how (trigers?) to extract file extensions for all rows? May be I have to create another table (because this one is replicated) and join them in 1:1 relation? Can you give me some advices please :)

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• When using Query Syntax in C# "Enumeration yielded no results". How to retrieve output

  - by Shantanu Gupta

  I have created this query to fetch some result from database. Here is my table structure. What exaclty is happening. DtMapGuestDepartment as Table 1 DtDepartment as Table 2 Are being used var dept_list= from map in DtMapGuestDepartment.AsEnumerable() where map.Field<Nullable<long>>("GUEST_ID") == DRowGuestPI.Field<Nullable<long>>("PK_GUEST_ID") join dept in DtDepartment.AsEnumerable() on map.Field<Nullable<long>>("DEPARTMENT_ID") equals dept.Field<Nullable<long>>("DEPARTMENT_ID") select dept.Field<string>("DEPARTMENT_ID"); I am performing this query on DataTables and expect it to return me a datatable. Here I want to select distinct department from Table 1 as well which will be my next quest. Please answer to that also if possible.

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• How to always return a set number of records when using find_related_tags with acts-as-taggable-on

  - by hadees

  I'm using the acts-as-taggable-on gem and I need to use find_related_tags on my survey model to get back 3 surveys every time. In the event there aren't always 3 related I need to pick how ever many are related plus some random ones to get to 3. Additionally I have a method I wrote called completed_survey_ids which return an array of survey_ids that shouldn't be used because the user has already completed them. Also there is a rare case that there won't be enough surveys because the user has completed them all so in that event it is okay to return less surveys then requested. I did write a named_scope to handle getting rid of the completed_survey_ids that I think works named_scope :not, lambda { |survey_ids| {:conditions => "id NOT IN (#{survey_ids.join(',')})" } }

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• Where can I find a jQuery color animation plugin?

  - by George Edison

  I need an up-to-date jQuery color animation plugin that works in IE 8. I tried using the one at http://plugins.jquery.com/project/color but it causes errors like "Invalid property value." in the following line of code from color.js: fx.elem.style[attr] = "rgb(" + [ Math.max(Math.min( parseInt((fx.pos * (fx.end[0] - fx.start[0])) + fx.start[0]), 255), 0), Math.max(Math.min( parseInt((fx.pos * (fx.end[1] - fx.start[1])) + fx.start[1]), 255), 0), Math.max(Math.min( parseInt((fx.pos * (fx.end[2] - fx.start[2])) + fx.start[2]), 255), 0) ].join(",") + ")"; Where can I get something that works? By the way, I really hate IE, if that helps.

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• python multiprocess update dictionary synchronously

  - by user1050325

  I am trying to update one common dictionary through multiple processes. Could you please help me find out what is the problem with this code? I get the following output: inside function {1: 1, 2: -1} comes here inside function {1: 0, 2: 2} comes here {1: 0, 2: -1} Thanks. from multiprocessing import Lock, Process, Manager l= Lock() def computeCopyNum(test,val): l.acquire() test[val]=val print "inside function" print test l.release() return a=dict({1: 0, 2: -1}) procs=list() for i in range(1,3): p = Process(target=computeCopyNum, args=(a,i)) procs.append(p) p.start() for p in procs: p.join() print "comes here" print a

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• Sample/Example needed for a table/field setup

  - by acctman

  Can someone explain the statement below to me with a working sample/example. thanks in advance. You can not create duplicate fields, but simply add a single extra field, "coupleId", which would have a unique id for each couple; and two rows (one for each person) per couple; then JOIN the table against itself with a constraint like a.coupleId = b.coupleId AND a.id < b.id so that you can condense the data into a single result row for a given couple.

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• How is a referencing environment generally implemented for closures?

  - by Alexandr Kurilin

  Let's say I have a statically/lexically scoped language with deep binding and I create a closure. The closure will consist of the statements I want executed plus the so called referencing environment, or, to quote this post, the collection of variables which can be used. What does this referencing environment actually look like implementation-wise? I was recently reading about ObjectiveC's implementation of blocks, and the author suggests that behind the scenes you get a copy of all of the variables on the stack and also of all the references to heap objects. The explanation claims that you get a "snapshot" of the referencing environment at the point in time of the closure's creation. Is that more or less what happens, or did I misread that? Is anything done to "freeze" a separate copy of the heap objects, or is it safe to assume that if they get modified between closure creation and the closure executing, the closure will no longer be operating on the original version of the object? If indeed there's copying being made, are there memory usage considerations in situations where one might want to create plenty of closures and store them somewhere? I think that misunderstanding of some of these concepts might lead to tricky issues like the ones Eric Lippert mentions in this blog post. It's interesting because you'd think that it wouldn't make sense to keep a reference to a value type that might be gone by the time the closure is called, but I'm guessing that in C# the compiler will figure out that the variable is needed later and put it into the heap instead. It seems that in most memory-managed languages everything is a reference and thus ObjectiveC is a somewhat unique situation with having to deal with copying what's on the stack.

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• How to make query on a property from a joined table in Hibernate using Criteria

  - by Palo

  Hello, I have the following mapping: <hibernate-mapping package="server.modules.stats.data"> <class name="User" table="user"> <id name="id"> <generator class="native"></generator> </id> <many-to-one name="address" column="addressId" unique="true" lazy="false" /> </class> <class name="Address" table="address"> <id name="id"> <generator class="native"></generator> </id> <property name="street" /> </class> </hibernate-mapping> How can I do a Criteria query to select all users living on some street? That is create Criteria query for this SQL: Select * from user join address on user.addressId = address.id where address.street='someStreet'

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• Doubt in Stored Procedure MySql - how to return multiple values for a variable ?

  - by Eternal Learner

  Hi, I have a stored procedure below. I intend this procedure to return the names of all the movies acted by an actor. Create Procedure ActorMovies( In ScreenName varchar(50), OUT Title varchar(50) ) BEGIN Select MovieTitle INTO Title From Movies Natural Join Acts where Acts.ScreenName = 'ScreenName '; End; I make a call like Call ActorMovies(' Jhonny Depp',@movie); Select @move; The result I get is a Null set , which is not correct.I am expecting a set of movies acted by Jhonny Depp to be returned. I am not sure as to why this is happening?

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• Possibility of a custom Contacts field with a set list of values and Contacts lookup performance

  - by areyling

  I'm pretty sure it's not viable to do what I'd like to based on some initial research, but I figured it couldn't hurt to ask the community of experts here in case someone knows a way. I'd like to create a custom field for contacts that the user is able to edit from the main Contacts app; however, the user should only be allowed to select from a list of four specific values. A short list of string values would be ideal, but an int with a min/max range would suffice. I'm interested in knowing if it's possible either way, but also wondering if it make sense to go this route performance wise. More specifically, would it be better to look up a contact (based on a phone number) each time a call or SMS message is received or better to store my own set of data (consisting of name, numbers, and the custom field) and just syncing contact info in a thread every so often? Or syncing contacts the first time the app is run and then registering for changes using ContentObserver? Here is a similar question with an answer that explains how to add a custom field to a contact. Thanks in advance.

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• sql server swap data between rows problem

  - by AmRoSH

  I was asking b4 about swaping query to swap data between rows in same table and i got that qurey ALTER PROCEDURE [dbo].[VehicleReservationsSwap] -- Add the parameters for the stored procedure here (@FirstVehicleID int, @secondVehicleID int, @WhereClause nvarchar(2000)) AS BEGIN Create Table #Temp ( VehicleID int ,VehicleType nvarchar(100) ,JoinId int ) DECLARE @SQL varchar(8000) SET @SQL ='Insert into #Temp (VehicleID,VehicleType,JoinId) SELECT VehicleID,VehicleType,CASE WHEN VehicleID = ' + Cast(@FirstVehicleID as varchar(10)) + ' then ' + Cast(@secondVehicleID as varchar(10)) + ' ELSE ' + Cast(@FirstVehicleID as varchar(10)) + ' END AS JoinId FROM Reservations WHERE VehicleID in ( ' + Cast(@FirstVehicleID as varchar(10)) + ' , ' + Cast(@secondVehicleID as varchar(10)) + ' )' + @WhereClause EXEC(@SQL) --swap values UPDATE y SET y.VehicleID = #Temp.VehicleID ,y.VehicleType = #Temp.VehicleType FROM Reservations y INNER JOIN #Temp ON y.VehicleID = #Temp.JoinId WHERE y.VehicleID in (@FirstVehicleID,@secondVehicleID) Drop Table #Temp END this query take 2 parameters and swaping all rows returned for each parameter. the problem is the query swaps just if each parameter (forign key) has values I need to make swaping in case if one of them has no vlue. I hope if some one can help me in that . Thanks,

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• Removing duplicate SQL records to permit a unique key

  - by j pimmel

  I have a table ('sales') in a MYSQL DB which should have rightfully have had a unique constraint enforced to prevent duplicates. To first remove the dupes and set the constraint is proving a bit tricky. Table structure (simplified): 'id (unique, autoinc)' product_id The goal is to enforce uniqueness for product_id. The de-duping policy I want to apply is to remove all duplicate records except the most recently created, eg: the highest id Or to put another way, I would like to delete duplicate records, excluding the ids matched by the following query: select id from sales s inner join (select product_id, max(id) as maxId from sales group by product_id having count(product_id) > 1) groupedByProdId on s.product_id and s.id = groupedByProdId.maxId I've struggled with this on two fronts - writing the query to select the correct records to delete and then also the constraint in MYSQL where a subselect FROM clause of a DELETE cannot reference the same table from which data is being removed.

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• Better use a tuple or numpy array for storing coordinates

  - by Ivan

  Hi, I'm porting an C++ scientific application to python, and as I'm new to python, some problems come to my mind: 1) I'm defining a class that will contain the coordinates (x,y). These values will be accessed several times, but they only will be read after the class instantiation. Is it better to use an tuple or an numpy array, both in memory and access time wise? 2) In some cases, these coordinates will be used to build a complex number, evaluated on a complex function, and the real part of this function will be used. Assuming that there is no way to separate real and complex parts of this function, and the real part will have to be used on the end, maybe is better to use directly complex numbers to store (x,y)? How bad is the overhead with the transformation from complex to real in python? The code in c++ does a lot of these transformations, and this is a big slowdown in that code. 3) Also some coordinates transformations will have to be performed, and for the coordinates the x and y values will be accessed in separate, the transformation be done, and the result returned. The coordinate transformations are defined in the complex plane, so is still faster to use the components x and y directly than relying on the complex variables? Thank you

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• Mysql Performance Question - Essentially about normalizing efficiency

  - by freqmode

  Hi there. Just a quick question about database performance. I'll outline my site purpose below as background. I'm creating a dictionary site that saves the words users define to a database. What I'm wondering is whether or not to create a words table for each user or to keep one massive words table. This site will be used for entire schools so the single words table would be massive! The database structure is as follows: A user table with: User_ID PRIMARY KEY Username First Last Password Email Country Research Standings SendInfo Donated JoinedOn LastLogin Logins Correct Attempts Admin Active And one word table with: User_ID PRIMARY KEY Word Vocab Spell Defined DefinedAttempted Spelled SpelledAttempted Sentenced SentencedAttempted So what I'm asking is , performance-wise, should I create a new table for each user when they join the site - each user could have hundreds or thousands of words over time? Or is it better to have one massive table with thousands and thousands of records and filter by User_ID. I don't think I'll perform many table joins. My gut feeling is to create a new table for each user, but I thought I'd ask for expert advice! Thanks in advance.

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• How do I list all non-system stored procedures?

  - by bubbassauro

  I want to create a query to list of all user defined stored procedures, excluding the ones that are system stored procedures, considering that: Checking the name like "sp_" doesn't work because there are user stored procedures that start with "sp_". Checking the property is_ms_shipped doesn't work because there are system stored procedures that have that flag = 0, for example: sp_alterdiagram (it is not MSShipped but appears under System Stored Procedures in SQL Server Management Studio). There must be a property, or a flag somewhere since you can see the "System Stored Procedures" in a separate folder in SQL 2005. Does anyone know? Edit: A combination of the suggestions below worked for me: select * from sys.objects O LEFT OUTER JOIN sys.extended_properties E ON O.object_id = E.major_id WHERE O.name IS NOT NULL AND ISNULL(O.is_ms_shipped, 0) = 0 AND ISNULL(E.name, '') <> 'microsoft_database_tools_support' AND O.type_desc = 'SQL_STORED_PROCEDURE' ORDER BY O.name

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• How to sum up an array of integers in C#

  - by Filburt

  Is there a better shorter way than iterating over the array? int[] arr = new int[] { 1, 2, 3 }; int sum = 0; for (int i = 0; i < arr.Length; i++) { sum += arr[i]; } clarification: Better primary means cleaner code but hints on performance improvement are also welcome. (Like already mentioned: splitting large arrays). It's not like I was looking for killer performance improvement - I just wondered if this very kind of syntactic sugar wasn't already available: "There's String.Join - what the heck about int[]?".

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• Allowing New Users to Invite Their Gmail Contacts

  - by John

  Hello, For my site, I would like to give new users the option to invite all of their Gmail contacts to join. What is the basic step-by-step process to set this up? (Also, is it necessary to buy an SSL for this?) Thanks in advance, John EDIT: My site has a basic login where users set up a username and password. I would like to give users the option to invite their Gmail contacts right after they create their new profile. I would also like to give them the option to invite their Gmail contacts anytime they want.

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• How to dynamically modify NHibernate load queries at runtime? EventListeners? Interceptors?

  - by snicker

  I need to modify the query used to load many-to-one references in my model. Specifically, I need to be able to further filter this data. Unfortunately, NH will not allow me to filter many-to-one relationships using the built in filtering system (?). I could just be doing something incorrect. Is there a hook where I can manually and dynamically modify the query used to load the data? Or an alternative to filters that will allow me to specify parameters? Background: I am working with a database that is using a form of revision control, with each entity having a natural ID PK, an EntityId, a RevisionValidTo and RevisionValidFrom field. There may be many rows using the same EntityId, which is the reference for other tables to join on, but the Revision ranges are mutually exclusive. Thus, the relationship is only many-to-one IIF the filter is applied. However, NH offers no way to specify a filter on many-to-one references (they do for collections...)

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• Nested sql queries in rails when :has_and_belongst_to_many

  - by Godisemo

  Hello, In my application I the next task that has not already been done by a user. I have Three models, A Book that has many Tasks and then I have a User that has has and belongs to many tasks. The table tasks_users table contains all completed tasks so I need to write a complex query to find the next task to perform. I have came up with two solutions in pure SQL that works, but I cant translate them to rails, thats what I need help with SELECT * FROM `tasks` WHERE `tasks`.`book_id` = @book_id AND `tasks`.`id` NOT IN ( SELECT `tasks_users`.`task_id` FROM `tasks_users` WHERE `tasks_users`.`user_id` = @user_id) ORDER BY `task`.`date` ASC LIMIT 1; and equally without nested select SELECT * FROM tasks LEFT JOIN tasks_users ON tasks_users.tasks_id = task.id AND tasks_users.user_id = @user_id WHERE tasks_users.task_id IS NULL AND tasks.book_id = @book_id LIMIT 1; This is what I Have done in rails with the MetaWhere plugin book.tasks.joins(:users.outer).where(:users => {:id => nil}) but I cant figure out how to get the current user there too, Thanks for any help!

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• Exception handling in Linq to SQL for customers without orders

  - by stackoverflowuser

  I have the following code to retrieve customer name, total (orders ), sum (order details) for reach customer in Northwind database. The problem with below code is that it raises an exception since a few customers dont have any entry in orders table. I know using the query syntax (join) the exception can be avoided. I want to know if the same can be handled with the extension method syntax. var customerOrders = db.Customers .Select(c => new { CompanyName = c.CompanyName, TotalOrders = c.Orders.Count(), TotalQuantity = c.Orders .SelectMany(o => o.Order_Details).Sum(o=>o.Quantity) });

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• The use of GROUP BY in MySQL

  - by Gustav Bertram

  I'm fishing for a comprehensive and canonical answer for the typical "mysql group by?" question. Here is some sample data: TABLE A +------+------+----------+-----+ | id | foo | bar | baz | +------+------+----------+-----+ | 1 | 1 | hello | 42 | | 2 | 0 | apple | 96 | | 3 | 20 | boot | 11 | | 4 | 31 | unicorn | 99 | | 5 | 19 | pumpkin | 11 | | 6 | 88 | orange | 13 | +------+------+----------+-----+ TABLE B +------+------+ | id | moo | +------+------+ | 1 | 1 | | 2 | 99 | | 3 | 11 | +------+------+ Demonstrate and explain the correct use of the GROUP BY clause in MySQL. Touch upon the following points: The use of MIN, MAX, SUM, AVG The use of HAVING Grouping by date, and ranges of dates Grouping with an ORDER BY Grouping with a JOIN Grouping on multiple columns Bonus points for references to other great answers, the MySQL online manual, and online tutorials on GROUP BY.

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• Type or namespace name could not be found

  - by Pandiya Chendur

  I use this: public IQueryable<MaterialsView> FindAllMaterials() { var materials = from m in db.Materials join Mt in db.MeasurementTypes on m.MeasurementTypeId equals Mt.Id select new MaterialsView { MatId = m.Mat_Name, MesName = Mt.Name, MesType = m.Mat_Type }; return materials; } It gives me the following errors: The type or namespace name MaterialsView could not be found (are you missing a using directive or an assembly reference?) Cannot implicitly convert type System.Collections.Generic.IEnumerable<MaterialsView> to System.Linq.IQueryable<MaterialsView>. An explicit conversion exists (are you missing a cast?) The type arguments for method System.Linq.Enumerable.ToList<TSource>(System.Collections.Generic.IEnumerable<TSource>) cannot be inferred from the usage. Try specifying the type arguments explicitly. I have googled it and found this SO question but it doesn't help. What's wrong?

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• VendInvoiceJour.InvoiceAccount <- VendTable.AccountNum relation

  - by vukis

  Hi. I have following situation: I need to join VendInvoiceJour.InvoiceAccount <- VendTable.AccountNum and take VendTable.Vendgroup. In all cases (queries,or even views) Dynamics ax joins tables VendInvoiceJour.OrderAccount<- VendTable.AccountNum not VendInvoiceJour.InvoiceAccount <- VendTable.AccountNum. I`m trying to use this kind of query: qBdSVendJour = element.query().dataSourceTable(tablenum(VendInvoiceJour)); qBdSVendTbl = qBdSVendJour.addDataSource(tablenum(VendTable)); qBdSVendTbl.relations(true); qBdSVendTbl.joinMode(JoinMOde::InnerJoin); qBdSVendTbl.fetchMode(QueryFetchMode::One2One); qBdSVendTbl.addLink(FieldNum(VendInvoiceJour,InvoiceAccount),FieldNum(VendTable,AccountNum));//(Dynamics ax automaticaly corrects InvoiceAccount to orderaccount in reports if trying this link in morphx)

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• Nested Select in Rails

  - by James

  I am working on a Rails application which uses categories for items. My category model is self-joined so that categories can be nested: class Category < ActiveRecord::Base has_many :items # Self Join (categories can have subcategories) has_many :subcategories, :class_name => "Category", :foreign_key => "parent_id" belongs_to :parent, :class_name => "Category" ... end I have a form which allows a user to create an item which currently lists all categories in a select, but they are all listed together: <%= f.label :category_id %> <%= select :item, :category_id, Category.all.collect {|c| [ c.title, c.id ]} %> So the select looks something like this: Category1 Category2 Category3BelongsTo2 Category4BelongsTo1 But what I want is: Category1 - Category4BelongsTo1 Category2 - Category3BelongsTo2 Is there a helper for this (which would be awesome!)? If not, how could I accomplish this? Thanks!

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