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• How can one manage to fully use the newly enhanced Parallelism features in .NET 4.0?

  - by Will Marcouiller

  I am pretty much interested into using the newly enhanced Parallelism features in .NET 4.0. I have also seen some possibilities of using it in F#, as much as in C#. Despite, I can only see what PLINQ has to offer with, for example, the following: var query = from c in Customers.AsParallel() where (c.Name.Contains("customerNameLike") select c; There must for sure be some other use of this parallelism thing. Have you any other examples of using it? Is this particularly turned toward PLINQ, or are there other usage as easy as PLINQ? Thanks! =)

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• Calculating holidays

  - by Ralph Shillington

  A number of holidays move around from year to year. For example, in Canada Victoria day (aka the May two-four weekend) is the Monday before May 25th, or Thanksgiving is the 2nd Monday of October (in Canada). I've been using variations on this Linq query to get the date of a holiday for a given year: var year = 2011; var month = 10; var dow = DayOfWeek.Monday; var instance = 2; var day = (from d in Enumerable.Range(1,DateTime.DaysInMonth(year,month)) let sample = new DateTime(year,month,d) where sample.DayOfWeek == dow select sample).Skip(instance-1).Take(1); While this works, and is easy enough to understand, I can imagine there is a more elegant way of making this calculation versus this brute force approach. Of course this doesn't touch on holidays such as Easter and the many other lunar based dates.

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• How to index a date column with null values?

  - by Heinz Z.

  How should I index a date column when some rows has null values? We have to select rows between a date range and rows with null dates. We use Oracle 9.2 and higher. Options I found Using a bitmap index on the date column Using an index on date column and an index on a state field which value is 1 when the date is null Using an index on date column and an other granted not null column My thoughts to the options are: to 1: the table have to many different values to use an bitmap index to 2: I have to add an field only for this purpose and to change the query when I want to retrieve the null date rows to 3: locks tricky to add an field to an index which is not really needed What is the best practice for this case? Thanks in advance Some infos I have read: Oracle Date Index When does Oracle index null column values?

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• pipelined function

  - by user289429

  Can someone provide an example of how to use parallel table function in oracle pl/sql. We need to run massive queries for 15 years and combine the result. SELECT * FROM Table(TableFunction(cursor(SELECT * FROM year_table))) ...is what we want effectively. The innermost select will give all the years, and the table function will take each year and run massive query and returns a collection. The problem we have is that all years are being fed to one table function itself, we would rather prefer the table function being called in parallel for each of the year. We tried all sort of partitioning by hash and range and it didn't help. Also, can we drop the keyword PIPELINED from the function declaration? because we are not performing any transformation and just need the aggregate of the resultset.

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• SQL: How can i update a value on a column only if that value is null?

  - by user321185

  Hey, I have an SQL question which may be basic to some but is confusing me. Here is an example of column names for a table 'Person': PersonalID, FirstName, LastName, Car, HairColour, FavDrink, FavFood Let's say that I input the row: 121312, Rayna, Pieterson, BMW123d, Brown, NULL, NULL Now I want to update the values for this person, but only if the new value is not null, Update: 121312, Rayna, Pieterson, NULL, Blonde, Fanta, NULL The new row needs to be: 121312, Rayna, Pieterson, BMW123d, Blonde, Fanta, NULL So I was thinking something along the lines of: Update Person(PersonalID, FirstName, LastName, Car, HairColour, FavDrink, FavFood) set Car = @Car (where @Car is not null), HairColour = @HairColour (where @HairColour...)... etc. My only concern is that I can't group all the conditions at the end of the query because it will require all the values to have the same condition. Can't i do something like Update HairColour if @HairColour is not Null

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• Rails Multiple Table Inheritance question

  - by Tony

  I am starting to implement an MTI solution and have a basic question. I have 3 physical models - SMSNotifications, EmailNotifications, TwitterNotifications and they are subclasses of notification. At times in my code, I want to say Notifications.find(:all)so that I can get a set of results sorted by their creation time. Then I want to do things based on their subclass. What is the way to write Notifications.find(:all) and have Rails look through the subclass tables and combine the results? Right now Rails still thinks I have a physical Notifications table which goes against my MTI design. I am also considering the possibility that I should be using STI instead. I would probably have 10 empty columns per row but if getting all notifications requires a query for each type of notification, then I feel like this could be a big issue. Thanks!

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• how can i write a Broadcast Receiver that will be invoked when user clicks on any application icon.

  - by chinnuthelearner

  hai every one, i have a query. how can i write a Broadcast Receiver that will be invoked when user clicks on any application icon. i tried by writing but it is not called. i tried, by using Packagemanager i will get ApplicationInfo from that i can know all the application starting activity name and package names. i thought i can use them to registerReceiver and my receiver will listen by its launching activity and package name. but i strucked.. i am unable to do that.. i think i lost the way.. please guide me...

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• Simplest way to use a DatagridView with Linq to SQL

  - by Martín Marconcini

  Hi, I have never used datagrids and such, but today I came across a simple problem and decided to "databind" stuff to finish this faster, however I've found that it doesn't work as I was expecting. I though that by doing something as simple as: var q = from cust in dc.Customers where cust.FirstName == someString select cust; var list = new BindingList<Customer>(q.ToList()); return list; Then using that list in a DataGridView1.DataSource was all that I needed, however, no matter how much I google, I can't find a decent example on how to populate (for add/edit/modify) the results of a single table query into a DataGridView1. Most samples talk about ASP.NET which I lack, this is WinForms. Any ideas? I've came across other posts and the GetNewBindingList, but that doesn't seem to change much. What am I missing (must be obvious)? Thanks in advance. Martin.

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• Rails ActiveRecord- has_many through and belongs_to a related model

  - by Nick

  I have 3 models sites, user_favorites and users. Relevant relationships: class Site < ActiveRecord::Base has_many :users, :through => :user_favorites class UserFavorite < ActiveRecord::Base belongs_to :user, :counter_cache => true belongs_to :site end class User < ActiveRecord:Base has_many :user_favorites has_many :sites, :through => :user_favorites All of that works just fine. I'd like to add a new attribute to the Site model to indicate which user created it. I don't believe this constitutes a has_and_belongs_to_many scenario. A site has many users through user_favorites but I want it to belong to a single user reflecting the owner/creator. I'm wondering what the ORM best practice is for this. SQL wise I'd just use different joins depending on what I was trying to query with a created_by FK in Site. Sorry if I'm missing something basic here. Thanks

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• Finding changes in MongoDB database

  - by Jonathan Knight

  I'm designing a MongoDB database that works with a script that periodically polls a resource and gets back a response which is stored in the database. Right now my database has one collection with four fields , id, name, timestamp and data. I need to be able to find out which names had changes in the data field between script runs, and which did not. In pseudocode, if(data[name][timestamp]==data[name][timestamp+1]) //data has not changed store data in collection 1 else //data has changed between script runs for this name store data in collection 2 Is there a query that can do this without iterating and running javascript over each item in the collection? There are millions of documents, so this would be pretty slow. Should I create a new collection named timestamp for every time the script runs? Would that make it faster/more organized? Is there a better schema that could be used? The script runs once a day so I won't run into a namespace limitation any time soon.

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• problem with doctrine:build-schema

  - by Ying

  Hi, im using symfony with doctrine, and Im trying to generate the schema yml file from a db. I get an this error SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'group' at line 1. Failing Query: "DESCRIBE group"I have a table named group in my database, and I suspect that this is screwing it up. Its not access problems as ive checked my db previleges. Any suggestions on what I can do? I have tried the quote-identifier attribute but with no luck : ( Im also struggling to find some good doctrine documentation. i cant seem to find where a list of attributes are, say for a creating a column in the schema.yml file. I tried reaching out to symfony forums but they are not responsive! Any help would be greatly appreciated! Thanks..

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• Get only latest row, grouped by a column

  - by Cylindric

  I have a large data-set of emails sent and status-codes. ID Recipient Date Status 1 [email protected] 01/01/2010 1 2 [email protected] 02/01/2010 1 3 [email protected] 01/01/2010 1 4 [email protected] 02/01/2010 2 5 [email protected] 03/01/2010 1 6 [email protected] 01/01/2010 1 7 [email protected] 02/01/2010 2 In this example: all emails sent to someone have a status of 1 the middle email (by date) sent to them has a status of 2, but the latest is 1 the last email sent to others has a status of 2 What I need to retrieve is a count of all emails sent to each person, and what the latest status code was. The first part is fairly simple: SELECT Recipient, Count(*) EmailCount FROM Messages GROUP BY Recipient ORDER BY Recipient Which gives me: Recipient EmailCount [email protected] 2 [email protected] 3 [email protected] 2 How can I get the most recent status code too? The end result should be: Recipient EmailCount LastStatus [email protected] 2 1 [email protected] 3 1 [email protected] 2 2 Thanks. (Server is Microsoft SQL Server 2008, query is being run through an OleDbConnection in .Net)

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• Can't use where clause on correlated columns.

  - by Keyo

  I want to add a where clause to make sure video_count is greater than zero. Only categories which are referenced once or more in video_category.video_id should be returned. Because video_count is not a field in any table I cannot do this. Here is the query. SELECT category . * , ( SELECT COUNT( * ) FROM video_category WHERE video_category.category_id = category.category_id ) AS 'video_count' FROM category WHERE category.status = 1 AND video_count > '0' AND publish_date < NOW() ORDER BY updated DESC; Thanks for the help.

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• Software protection

  - by anfono

  I want to protect my software from being used without permission. I will provide it for free to the parties I authorize to use it. Anyone knows a good protection scheme against having it copied and run by unauthorized parties ? So far, I thought about introducing a key validation mechanism: periodically, the user needs to send me (web site query) a code based on which I generate a new code that app validates against. There is an initial code, and so I can track users... Thoughts ? Later edit: I changed the licensing part to avoid unfocused discussion.

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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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• Find overdrawn accounts in SQL

  - by mazzzzz

  Hey guys, I have a program that allows me to run queries against a large database. I have two tables that are important right now, Deposits and withdraws. Each contains a history of every user. I need to take each table, add up every deposit and withdraws (per user), then subtract the withdraws from the deposits. I then need to return every user whos result is negative (aka they withdrew more then they deposited). Is this possible in one query? Example: Deposit Table: |ID|UserName|Amount| |1 | Use1 |100.00| |2 | Use1 |50.00 | |3 | Use2 |25.00 | |4 | Use1 | 5.00 | WithDraw Table: |ID|UserName|Amount| |2 | Use2 | 5.00 | |1 | Use1 |100.00| |4 | Use1 | 5.00 | |3 | Use2 |25.00 | So then the result would output: |OverWithdrawers| | Use2 | Is this possible (I sure don't know how to do it)? Thanks for any help, Max

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• database vs flat file, which is a faster structure for regex matching with many simultaneous request

  - by Jamex

  Hi, which structure returns faster result and/or less taxing on the host server, flat file or database (mysql)? Assume many users (100 users) are simultaneously query the file/db. Searches involve pattern matching using regex against a static file/db. File has 50,000 unique lines (same data type). There could be many matches. There is no writing to the file/db, just read. Is it possible to have a duplicate the file/db and write a logic switch to use the backup file/db if the main file is in use? Which language is best for the type of structure? Perl for flat and PHP for db? TIA

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• Android: making a custom ListView independent of adapters ?

  - by wei

  I am adding a local database as a cache to a remote web service in my android application to answer queries. I used ArrayAdapters before for list views to display the results from the web service. Now with a database cache, the result could be either a Cursor(from database) or a List(from web), which means the adapter can be CursorAdapter or ArrayAdapter too. Creating two adapters for one query doesn't seem to be a good idea. So I am wondering what would be the best way to refactor my current code to add this database feature? Thanks,

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• database vs flat file, which is a faster structure for "regex" matching with many simultaneous reque

  - by Jamex

  Hi, which structure returns faster result and/or less taxing on the host server, flat file or database (mysql)? Assume many users (100 users) are simultaneously query the file/db. Searches involve pattern matching against a static file/db. File has 50,000 unique lines (same data type). There could be many matches. There is no writing to the file/db, just read. Is it possible to have a duplicate the file/db and write a logic switch to use the backup file/db if the main file is in use? Which language is best for the type of structure? Perl for flat and PHP for db? Addition info: If I want to find all the cities have the pattern "cis" in their names. Which is better/faster, using regex or string functions? Please recommend a strategy TIA

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• How to extract all IDs accessed from a mysql general log using the linux commandline?

  - by shlomoid

  This should be a trivial question for anyone who's good with bash/sed/awk. Unfortunately, I'm not, yet :) I've got a general log from MySQL which contains some queries that have a common parameter, they query on a specific id field. The queries look like update tbl set col='binary_values' where id=X; I need to process the log and extract all the IDs that these queries touched, each in it's own line. The purpose of this is to figure out how many times each ID is accessed. Eventually I'd group and count the values. The binary values are indeed binary junk, so they kinda messed up some things I've been trying to do. Eventually we solved the problem temporarily using a python script, but I'm sure the linux command line tool set can do it too. How would you do it?

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• Regex for finding valid sphinx fields

  - by mlissner

  I'm trying to validate that the fields given to sphinx are valid, but I'm having difficulty. Imagine that valid fields are cat, mouse, dog, puppy. Valid searches would then be: @cat search terms @(cat) search terms @(cat, dog) search term @cat searchterm1 @dog searchterm2 @(cat, dog) searchterm1 @mouse searchterm2 So, I want to use a regular expression to find terms such as cat, dog, mouse in the above examples, and check them against a list of valid terms. Thus, a query such as: @(goat) Would produce an error because goat is not a valid term. I've gotten so that I can find simple queries such as @cat with this regex: (?:@)([^( ]*) But I can't figure out how to find the rest. I'm using python & django, for what that's worth.

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• How do I sort feeds returned from Google Reader?

  - by Ed Marty

  When I query Google Reader for the list of subscriptions for a user, it seems to be returned in a fixed order, no matter what the order is as shown at google.com/reader. (see http://www.google.com/reader/api/0/subscription/list for the list I'm talking about) Each subscription returns a 'sortid', which Google Reader uses when the user rearranges subscriptions, by sending back a concatenation of all sortids in the new order after rearranging is finished. However, that sortid never changes. So my question is this: How do I actually get the order the subscriptions are supposed to be in? I've been using http://code.google.com/p/pyrfeed/wiki/GoogleReaderAPI as a reference, but it is lacking in this department, and I haven't found anything anywhere else either.

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• Google App Engine Database Index

  - by fjsj

  I need to store a undirected graph in a Google App Engine database. For optimization purposes, I am thinking to use database indexes. Using Google App Engine, is there any way to define the columns of a database table to create its index? I will need some optimization, since my app uses this stored undirected graph on a content-based filtering for item recommendation. Also, the recommender algorithm updates the weights of some graph's edges. If it is not possible to use database indexes, please suggest another method to reduce query time for the graph table. I believe my algorithm does more data retrieval operations from graph table than write operations. PS: I am using Python.

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• Best way to gather, then import data into drupal?

  - by Frank

  I am building my first database driven website with Drupal and I have a few questions. I am currently populating a google docs excel spreadsheet with all of the data I want to eventually be able to query from the website (after it's imported). Is this the best way to start? If this is not the best way to start what would you recommend? My plan is to populate the spreadsheet then import it as a csv into the mysql db via the CCK Node. I've seen two ways to do this. http://drupal.org/node/133705 (importing data into CCK nodes) http://drupal.org/node/237574 (Inserting data using spreadsheet/csv instead of SQL insert statements) Basically my question(s) is what is the best way to gather, then import data into drupal? Thanks in advance for any help, suggestions.

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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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