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• Aging Data Structure in C#

  - by thelsdj

  I want a data structure that will allow querying how many items in last X minutes. An item may just be a simple identifier or a more complex data structure, preferably the timestamp of the item will be in the item, rather than stored outside (as a hash or similar, wouldn't want to have problems with multiple items having same timestamp). So far it seems that with LINQ I could easily filter items with timestamp greater than a given time and aggregate a count. Though I'm hesitant to try to work .NET 3.5 specific stuff into my production environment yet. Are there any other suggestions for a similar data structure? The other part that I'm interested in is aging old data out, If I'm only going to be asking for counts of items less than 6 hours ago I would like anything older than that to be removed from my data structure because this may be a long-running program.

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• Is it worth caching a Dictionary for foreign key values in ASP.net?

  - by user169867

  I have a Dictionary<int, string> cached (for 20 minutes) that has ~120 ID/Name pairs for a reference table. I iterate over this collection when populating dropdown lists and I'm pretty sure this is faster than querying the DB for the full list each time. My question is more about if it makes sense to use this cached dictionary when displaying records that have a foreign key into this reference table. Say this cached reference table is a EmployeeType table. If I were to query and display a list of employee names and types should I query for EmployeeName and EmployeeTypeID and use my cached dictionary to grab the EmployeeTypeIDs name as each record is displayed or is it faster to just have the DB grab the EmployeeName and JOIN to get the EmployeeType string bypassing the cached Dictionary all together. I know both will work but I'm interested in what will perform the fastest. Thanks for any help.

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• How to achieve multiple grids like the SQL server Results pane

  - by Skun

  Hi guys ! I'm having problems with my project once again :( The front end is C# I need to support multiline querying like MS SQL server and when these queries are executed, naturally there are going to be multiple result sets. Getting the datatables respective to the results is not a problem, but how do i make it appear like its done in MS SQL server. One result set below the other and with a scroll bar? Should i bind it to a datagrid? If so how can i bind multiple tables to a datagrid ? and will it generate the scrollbars and the columns automatically? If i am not clear, please let me know and i'll try to be more clearer. ps: If anyone knows how this can be done with the XtraGridControl in devexpress that would be awesome ! :D

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• problem in basic implementation of MVVM pattern - Services

  - by netmajor

  I watch some video and read articles about MVVM pattern and start thinking how should I implement it in my Silverlight app. So at first I create Silverlight application. I think that for clear view I create 3 folders: View - for each user control page in my app, ViewModel - for c# class which will querying date and Model- Entity Data Model of my SQL Server or Oracle Database. And now I am confused, cause I want to implement *WCF/RIA Services/Web services* in my project. In which folder should I put in class of services? I see in examples that Services take date and filtering it and then output data was binding in View - so It looks as ViewModel. But I was sure that someone use Services in Model and that I want to do. But how? Can someone explain me implementing Services as Model? Is my point of view at MVVM is correctly?

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• Can DBRefs contain additional fields?

  - by Soviut

  I've encountered several situations when using MongoDB that require the use of DBRefs. However, I'd also like to cache some fields from the referenced document in the DBRef itself. {$ref:'user', $id:'10285102912A', username:'Soviut'} For example, I may want to have the username available even though the user document is referenced. This would provide me all the benefits of a single document approach; Faster querying and eliminating the need to do manual dereferencing in my code. While at the same time allowing me to use references where they make sense. The idea being that when the referenced document is updated (a user changes their name, for example) my business layer can automatically update all the documents that reference it. Ultimately, I'm wondering if it's considered good form to store additional fields on my DBRefs? Will it break anything? Will I lose my data each time a reference is rewritten? Will drivers like pymongo support it?

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• Shutting Down SSH Tunnel in Paramiko Programatically

  - by PlaidFan

  We are attempting to use the paramiko module for creating SSH tunnels on demand to arbitrary servers for purposes of querying remote databases. We attempted to use the forward.py demo that ships with paramiko but the big limitation is there does not seem to be an easy way to close an SSH tunnel and the SSH connection once the socket server is started up. The limitation we have is that we cannot activate this from a shell and then kill the shell manually to stop the listner. We need to open the SSH connection, tunnel, perform some actions through the tunnel, close the tunnel, and close the SSH connection within python. I've seen references to a server.shutdown() method but it isn't clear how to implement it correctly. Any help would be greatly appreciated...

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• ActiveMQ - Removing queues programatically

  - by Eduardo Z.

  Fellow StackOverflowers, is there a way for me to remove a queue or a topic in ActiveMQ programatically? I am using ActiveMQ's standard persistency, and my application requires that, on startup, all new queues be dynamically re-created (unless there are messages stored in the queue, in which case, the queue should remain to exist). I am also creating all queues programatically through sessions. Is there an equivalent to that procedure, only to delete a queue? Querying and iterating through the existing queues would also be useful, but i haven't found a way to do that yet. Please help an ActiveMQ noob! =)

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• Query DNSBL or other block lists using PHP

  - by 55skidoo

  Is there any way to use PHP code to query a DNSBL (block list) provider and find out if the IP address submitted is a bad actor? I would like to take an existing IP address out of a registration database, then check whether it's a known block-listed IP address by performing a lookup on it, then if it's a blacklisted, do an action on it (such as, delete entry from registration database). Most of the instructions I have seen assume you are trying to query the blocklist via a mail server, which I can't do. I tried querying via web browser by typing in queries such as "58.64.xx.xxx.dnsbl.sorbs.net" but that didn't work.

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• Intelligent serial port mocks with Moq

  - by Padu Merloti

  I have to write a lot of code that deals with serial ports. Usually there will be a device connected at the other end of the wire and I usually create my own mocks to simulate their behavior. I'm starting to look at Moq to help with my unit tests. It's pretty simple to use it when you need just a stub, but I want to know if it is possible and if yes how do I create a mock for a hardware device that responds differently according to what I want to test. A simple example: One of the devices I interface with receives a command (move to position x), gives back an ACK message and goes to a "moving" state until it reaches the ordered position. I want to create a test where I send the move command and then keep querying state until it reaches the final position. I want to create two versions of the mock for two different tests, one where I expect the device to reach the final position successfully and the other where it will fail. Too much to ask?

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• Use ASP.NET Profile or not?

  - by DotnetDude

  I need to store a few attributes of an authenticated user (I am using Membership API) and I need to make a choice between using Profiles or adding a new table with UserId as the PK. It appears that using Profiles is quick and needs less work upfront. However, I see the following downsides: The profile values are squished into a single ntext column. At some point in the future, I will have SQL scripts that may update user's attributes. Querying a ntext column and trying to update a value sounds a little buggy to me. If I choose to add a new user specific property and would like to assign a default for all the existing users, would it be possible? My first impression has been that using profiles may cause maintainance headaches in the long run. Thoughts?

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• Where should the partitioning column go in the primary key on SQL Server?

  - by Bialecki

  Using SQL Server 2005 and 2008. I've got a potentially very large table (potentially hundreds of millions of rows) consisting of the following columns: CREATE TABLE ( date SMALLDATETIME, id BIGINT, value FLOAT ) which is being partitioned on column date in daily partitions. The question then is should the primary key be on date, id or value, id? I can imagine that SQL Server is smart enough to know that it's already partitioning on date and therefore, if I'm always querying for whole chunks of days, then I can have it second in the primary key. Or I can imagine that SQL Server will need that column to be first in the primary key to get the benefit of partitioning. Can anyone lend some insight into which way the table should be keyed?

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• XmlDocument caching memory usage

  - by mdsharpe

  We are seeing very high memory usage in .NET web applications which use XmlDocument. A small (~5MB) XML document is loaded into an XmlDocument object and stored in HttpContext.Cache for easy querying and XSLT transformation on each page load. The XML is modified on disk periodically so a cache has a dependency on the file. Such an application appears to be using hundreds of megabytes of RAM. I have experimented with requesting garbage collection on each request start, and this keeps the RAM usage far lower but I cannot imagine this is good practise. Does anyone have any suggestions as to how we can achieve the same goal but with lower RAM usage?

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• Is it actually possible to connect to ActiveMQ via XMPP and query/browse queues using "AciveMQ.Agen

  - by Oleg Kiorsak

  I tried what I think are 4 most popular XMPP (aka "Jabber") clients (Spark, Pidgin, Psi, Pandion) to connect to ActiveMQ instance (Apache ActiveMQ ver. 5.3.0) on XMMP connector with an idea to use the "AciveMQ.Agent chatroom" for querying queues/etc and no success at all Some of them fail with 'Unknown error', some don't fail but kind of "hang"... interestingly, some communication does indeed reach the ActiveMQ side, because when I close a client it spits an exception "could not close" or something to that effect... and if I try "register new user" option (present on most clients" the ActiveMQ also spits some most cryptic warning message But I was never able to get to the point when I could see or specify "ActiveMQ.Agent" as chatroom and issue any commands... Before I waste any more time on this curious feature, I would like to hear whether anyone had any success with it? Thank you! PS: BTW, the book "ActiveMQ in Action book" http://www.manning.com/snyder/ shows that it is apparently works and is very easy using some Mac client (AdiumX), but I wanted it on a Windows PC ;)

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• Linq to NHibernate using Queryable.Where predicate

  - by Groo

  I am querying an SQLite database using LINQ to NHibernate. Person is an entity containing an Id and a Name: public class Person { public Guid Id { get; private set; } public string Name { get; private set; } } Let's say my db table contains a single person whose name is "John". This test works as expected: var query = from item in session.Linq<Person>() where (item.Name == "Mike") select item; // no such entity should exist Assert.IsFalse(query.Any()); but this one fails: var query = from item in session.Linq<Person>() select item; query.Where(item => item.Name == "Mike"); // following line actually returns the // "John" entry Assert.IsFalse(query.Any()); What am I missing?

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• Oracle - Is there any effects of not having a primary key on a table ?

  - by Sathya

  We use sequence numbers for primary keys on the tables. There are some tables where we dont really use the primary key for any querying purpose. But, we have Indexes on other columns. These are non-unique indexes. The queries use these non-primary key columns in the WHERE conditions. So, I dont really see any benefit of having a primary key on such tables. My experience with SQL 2000 was that, it used to replicate tables which had some primary key. Otherwise it would not. I am using Oracle 10gR2. I would like to know if there are any such side-effects of having tables that dont have primary key.

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• Use SQL to filter the results of a stored procedure

  - by Ben McCormack

  I've looked at other questions on Stack Overflow related to this question, but none of them seemed to answer this question clearly. We have a system Stored Procedure called sp_who2 which returns a result set of information for all running processes on the server. I want to filter the data returned by the stored procedure; conceptually, I might do it like so: SELECT * FROM sp_who2 WHERE login='bmccormack' That method, though, doesn't work. What are good practices for achieving the goal of querying the returned data of a stored procedure, preferably without having to look of the code of the original stored procedure and modify it.

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• How to create a custom ADO Multi Demensional Catalog with no database

  - by Alan Clark

  Does anyone know of an example of how to dynamically define and build ADO MD (ActiveX Data Objects Multidimensional) catalogs and cube definitions with a set of data other than a database? Background: we have a huge amount of data in our application that we export to a database and then query using the usual SQL joins, groups, sums etc to produce reports. The data in the application is originally in objects and arrays. The problem is the amount of data is so large the export can take 2 hours. So I am trying to figure out a good way of querying the objects in memory, either by a custom OLAP algorithm or library, or ADO MD. But I haven't been able to find an example of using ADO MD without a database behind it. We are using Delphi 2010 so would use ADO ActiveX but I imagine the ADO.NET MD is similar. I realize that if the application data was already stored in a database the problem would solve itself. Also if Delphi had LINQ capability I could query the objects and arrays that way.

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• Is it possible to have a tableless select with multiple rows?

  - by outis

  A SELECT without a FROM clause gets us a multiple columns without querying a table: SELECT 17+23, REPLACE('bannanna', 'nn', 'n'), RAND(), CURRENT_TIMESTAMP; How can we write a query that results in multiple rows without referring to a table? Basically, abuse SELECT to turn it into a data definition statement. The result could have a single column or multiple columns. I'm most interested in a DBMS neutral answer, but others (e.g. based on UNPIVOT) are welcome. There's no technique application behind this question; it's more theoretical than practical.

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• App-Engine (Java) File Upload

  - by Manjoor

  I managged to upload files on app-engine by using the following example http://stackoverflow.com/questions/1513603/how-to-upload-and-store-an-image-with-google-app-engine-java and http://www.mail-archive.com/[email protected]/msg08090.html The problem is, I am sumitting other fields along with file field as listed below <form action="index.jsp" method="post" enctype="multipart/form-data"> <input name="name" type="text" value=""> <br/> <input name="imageField" type="file" size="30"> <br/> <input name="Submit" type="submit" value="Sumbit"> </form> In my servlet I am getting null when querying name = request.getParameter("name"); Why it is so? Is there a way to retrieve text field value?

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• How to control the memory size of continuously running windows service?

  - by Snowill

  Hi, I have created a windows service which is continuously polling a database. For this purpose i have a timer in place. Ever time i am querying a database table i open a connection and close it immediately after my work is done. Right now i am doing this every 20 seconds for testing purpose, but later this time might increase to 5 - 10 minutes. What happens is everytime the database table is polled there is an increase of 10-12 KB in the size of the memory of the service running. This i can see in the task manager. Is there any way to control this.

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• Indexing SET field

  - by Dienow

  I have two entities A and B. They are related with many to many relation. Entity A can be related up to 100 B entities. Entity B can be related up to 10000 A entities. I need quick way to select for example 30 A entities, that have relation with specified B entities, filtered and sorted by different attributes. Here how I see ideal solution: I put all information I know about A entities, including their relations with B entities into single row (Special table with SET field) then add all necessary indexes. The problem is that you can't use index while querying by SET field. What should I do? I can replace database with something different, if that'll help.

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• Low cost way to host a large table yet keep the performance scalable?

  - by Leo Liang

  I have a growing table storing time series data, 500M entries now, and 200K new records every day. The total size is around 15GB for now. My clients are querying the table via a PHP script mostly, and the size of the result set is around 10K records (not very large). select * from T where timestamp > X and timestamp < Y and additionFilters And I want this operation cheap. Currently my table is hosting in Postgres 7, on a single 16G memory Box, and I would love to see some good suggestion for me to host this in low cost and also allow me to scale up for performance if needed. The table serves: 1. Query: 90% 2. Insert: 9.9% 2. Update: 0.1% <-- very rare.

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• Error loading SQL_VARIANT data type using Python

  - by Brett D

  I am using Python and SQLAlchemy to query a database that I did not create. I have run into a problem querying a table that contains the SQL_VARIANT data type. I get the error: sqlalchemy.exc.DBAPIError: (Error) ('ODBC data type -150 is not supported. Cannot read column Value.', 'HY000') I confirmed with the database creator that the "Value" column is of type SQL_VARIANT. Does anyone know a way to load this data type using Python? I am currently using mssql with pyodbc. Thank you for any help you can offer! Versions: Python 2.7, SQLAlchemy 0.7.8

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• View a SYS.XMLTYPE returned from an Oracle function, using PL/SQL

  - by caerphilly

  I have an Oracle function that dynamically creates an XML document, and returns it in a SYS.XMLTYPE value. I want to run a query from SQL Developer that calls that function and prints the document (either via a select, or dbms_output - I don't care). But all the examples/documentation seem to refer to querying XML columns in tables, and I can't seem to get the syntax right for my particular usage. I'd like something like this: declare x SYS.XMLTYPE; begin x := my_package.my_function(); select x.getclobval() from x; -- doesn't work! end; How can I print out the value of the XML type variable 'x' in the above code?

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• How can I organize many results in a selectbox using php?

  - by zeckdude

  I have a select box that is part of a form. It is currently querying the addresses table and displaying the addresses into the select box. I plan on having up to 100 addresses. I'm looking for a solution where I can show all the states if the user clicks on the select box. Then if the user hovers over a state it will show all the addresses for that specific state. Then if the user clicks on an address, it will show that as the picked option in the select box. This is like a dropdown menu within a select box. Does anyone know where I can find a solution as this?

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