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• How can i get notifications from server to android device?

  - by Vaibs

  I am creating a app wherein user shares some information. This data i am storing it in database through servlets i.e. i am calling my own servlets which will take data through url and store it in database. So i want other users of that same app to get notify that some information is available and in turn they will get the information that other user has updated. For this to work we can use polling or pusher. But polling will take lots of battery power. I have tried C2DM but its not working for me. So i am thinking for some other mechanism by which i can implement other than C2DM. Please suggest some way to work it. and e.g. if u have came across.

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• Want to build simple SQL admin interface to change a few values in a table.

  - by Adam McC

  i am currently building a system in MSSQL 2K5. i have a table that holds information about certain insurance schemes such as overheads and other things. these values will change occasionally and currently i administer the database straight through the management Studio. i would like to build a simple interface that will allow my colleagues to change these values by selecting the company in a dropdown and the current values will populate. they can then edit these values and submit them to the database. is this possible in the current Visual Studio supplied with MSSQL server 2K5 or do i need to get another product. i am confident that with the help of stack overflow and google i can build this myself, but i need pointed in the right direction as to which environment would be easiest and best to start building it. Many thanks, adam

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• Case insensitive string compare in LINQ-to-SQL

  - by BlueMonkMN

  I've read that it's unwise to use ToUpper and ToLower to perform case-insensitive string comparisons, but I see no alternative when it comes to LINQ-to-SQL. The ignoreCase and CompareOptions arguments of String.Compare are ignored by LINQ-to-SQL (if you're using a case-sensitive database, you get a case-sensitive comparison even if you ask for a case-insensitive comparison). Is ToLower or ToUpper the best option here? Is one better than the other? I thought I read somewhere that ToUpper was better, but I don't know if that applies here. (I'm doing a lot of code reviews and everyone is using ToLower.) Dim s = From row In context.Table Where String.Compare(row.Name, "test", StringComparison.InvariantCultureIgnoreCase) = 0 This translates to an SQL query that simply compares row.Name with "test" and will not return "Test" and "TEST" on a case-sensitive database.

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• Does anyone have a backup strategy for SQL Azure databases?

  - by Pete

  I'm using SQL Azure on a project and it works great. The problem is that the usual backup features do not exist. I have exported the database a couple of times using SQLAzureMW ( http://sqlazuremw.codeplex.com/ ) but this tool is now choking trying to download the database data with bcp. In any case, it's not as nice a solution as SQL Server backups. Is anyone aware of a commercial or open source tool, or other technique, for making reliable backups of SQL Azure databases? This is really a showstopper.

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• Sending BLOBs in a JSON service,... how?

  - by Marten Sytema

  Hello I have a webservice (ie. servlet) implemented in Java. It gets some data from a MySQL table, with one column being of type BLOB (an image), and some other columns are just plain text. Normally I would store the file outside the database with a pointer to it in the database, but due to circumstance I now have to use this BLOB column... What is the proper way to send this? How to encode the image in a JSONObject, and how to parse (and RENDER!) it on the otherside ? I want to use JSONP, to avoid having to proxy it through the consumer's webserver. So that the consumer can just put in a tag pointing to the webservice, calling a callback. Any thoughts how to handle images in this situation? Also thoughts on performance etc. are interesting!

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• How to implement a syndication receiver? (multi-client / single server)

  - by LeonixSolutions

  I have to come up with a system architecture. A few hundred remote devices will be communicating over internet with a central server which will receive data and store it in a database. I could write my own TCP/IP based protocol use SOAP use AJAX use RSS anything else? This is currently seen as one way (telemetry, as opposed to SCADA). Would it make a difference if we make it bi-directional. There are no plans to do so, but Murphy's law makes me wary of a uni-directional solution (on the data plane; I imagine that the control plane is bi-directional in all solutions (?)). I hope that this is not too subjective. I would like a solution which is quick and easy to implement and for others to support and where the general "communications pipeline" from remote deceives to database server can be re-used as the core of future projects. I have a strong background in telecomms protocols, in C/C++ and PHP.

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• When is a good time to start thinking about scaling?

  - by Slokun

  I've been designing a site over the past couple days, and been doing some research into different aspects of scaling a site horizontally. If things go as planned, in a few months (years?) I know I'd need to worry about scaling the site up and out, since the resources it would end up consuming would be huge. So, this got me to thinking, when is the best time to start thinking about, and designing for, scalability? If you start too early on, you could easily over complicate your design, and make it impossible to actually build. You could also get too caught up in the details, the architecture, whatever, and wind up getting nothing done. Also, if you do get it working, but the site never takes off, you may have wasted a good chunk of extra effort. On the other hand, you could be saving yourself a ton of effort down the road. Designing it from the ground up to be big would make it much easier later on to let it grow big, with very little rewriting going on. I know for what I'm working on, I've decided to make at least a few choices now on the side of scaling, but I'm not going to do a complete change of thinking to get it to scale completely. Notably, I've redesigned my database from a conventional relational design to one similar to what was suggested on the Reddit site linked below, and I'm going to give memcache a try. So, the basic question, when is a good time to start thinking or worrying about scaling, and what are some good designs, tips, etc. for when doing so? A couple of things I've been reading, for those who are interested: http://www.codinghorror.com/blog/2009/06/scaling-up-vs-scaling-out-hidden-costs.html http://highscalability.com/blog/2010/5/17/7-lessons-learned-while-building-reddit-to-270-million-page.html http://developer.yahoo.com/performance/rules.html

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• Large ResultSet on postgresql query

  - by tuler

  I'm running a query against a table in a postgresql database. The database is on a remote machine. The table has around 30 sub-tables using postgresql partitioning capability. The query will return a large result set, something around 1.8 million rows. In my code I use spring jdbc support, method JdbcTemplate.query, but my RowCallbackHandler is not being called. My best guess is that the postgresql jdbc driver (I use version 8.3-603.jdbc4) is accumulating the result in memory before calling my code. I thought the fetchSize configuration could control this, but I tried it and nothing changes. I did this as postgresql manual recomended. This query worked fine when I used Oracle XE. But I'm trying to migrate to postgresql because of the partitioning feature, which is not available in Oracle XE. My environment: Postgresql 8.3 Windows Server 2008 Enterprise 64-bit JRE 1.6 64-bit Spring 2.5.6 Postgresql JDBC Driver 8.3-603

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• Passing parameters to web service method in c#

  - by wafa.cs1

  Hello I'm developing an android application .. which will send location data to a web service to store in the server database. In Java: I've used REST protocol so the URI is: HttpPost request = new HttpPost("http://trafficmapsa.com/GService.asmx/GPSdata? lon="+Lon+"&Lat="+Lat+"&speed="+speed); In Asp.net (c#) web service will be: [WebMethod] public CountryName GPSdata(Double Lon, Double Lat, Double speed) { after passing the data from android ..nothing return in back .. and there is no data in the database!! Is there any library missing in the CS file!! I cannot figure out what is the problem.

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• how to run foreach loop with ternary condition

  - by I Like PHP

  i have two foreach loop to display some data, but i want to use a single foreach on basis of database result. means if there is any row returns from database then forach($first as $fk=>$fv) should execute otherwise foreach($other as $ok) should execute. i m unsing below ternary operator which gives parse error $n=$db->numRows($taskData); // databsse results <?php ($n) ? foreach ($first as $fk=>$fv) : foreach ($other as $ok) { ?> <table><tr><td>......some data...</td></tr></table> <?php } ?> please suggest me how to handle such condition via ternary operator or any other idea. Thanks

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• When should I open and close a connection to SQL Server

  - by Martin

  I have a simple static class with a few methods in it. Each of those methods open a SqlConnection, query the database and close the connection. This way, I am sure that I always close the connection to the database, but on the other hand, I don't like to always open and close connection. Below is an example of what my methods look like. public static void AddSomething(string something) { using (SqlConnection connection = new SqlConnection("...")) { connection.Open(); // ... connection.Close(); } } Considering that the methods are inside a static class, should I have a static member containing a single SqlConnection? How and when should I drop it? What are the best practices?

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• finding ALL cycles in a huge sparse matrix

  - by Andy

  Hi there, First of all I'm quite a Java beginner, so I'm not sure if this is even possible! Basically I have a huge (3+million) data source of relational data (i.e. A is friends with B+C+D, B is friends with D+G+Z (but not A - i.e. unmutual) etc.) and I want to find every cycle within this (not necessarily connected) directed graph. I've found this thread (http://stackoverflow.com/questions/546655/finding-all-cycles-in-graph/549402#549402) which has pointed me to Donald Johnson's (elementary) cycle-finding algorithm which, superficially at least, looks like it'll do what I'm after (I'm going to try when I'm back at work on Tuesday - thought it wouldn't hurt to ask in the meanwhile!). I had a quick scan through the code of the Java implementation of Johnson's algorithm (in that thread) and it looks like a matrix of relations is the first step, so I guess my questions are: a) Is Java capable of handling a 3+million*3+million matrix? (was planning on representing A-friends-with-B by a binary sparse matrix) b) Do I need to find every connected subgraph as my first problem, or will cycle-finding algorithms handle disjoint data? c) Is this actually an appropriate solution for the problem? My understanding of "elementary" cycles is that in the graph below, rather than picking out A-B-C-D-E-F it'll pick out A-B-F, B-C-D etc. but that's not the end of the world given the task. E / \ D---F / \ / \ C---B---A d) If necessary, I can simplify the problem by enforcing mutuality in relations - i.e. A-friends-with-B <== B-friends-with-A, and if really necessary I can maybe cut down the data size, but realistically it is always going to be around the 1mil mark. z) Is this a P or NP task?! Am I biting off more than I can chew? Thanks all, any help appreciated! Andy

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• How can I display characters in a map by mapfile?

  - by sirius

  Hello. I'm trying to show a map using postGIS+Mapserver.And I've displayed a PNG picture in my WEB. However, I want to show some charactors in the map, just like this: this is the example from Mapserver Now I'm using database(postgreSQL), but not a shape file. How can I add the charactors then? Here is a part of my mapfile: LAYER CONNECTIONTYPE postgis NAME "state" //Connect to a remote spatial database CONNECTION "user=postgres dbname=*** host=*** password=***" PROCESSING "CLOSE_CONNECTION=DEFER" DATA "the_geom from province" STATUS ON TYPE POLYGON CLASS STYLE COLOR 122 122 122 OUTLINECOLOR 0 0 0 END LABEL COLOR 132 31 31 SHADOWCOLOR 218 218 218 SHADOWSIZE 2 2 TYPE TURETYPE FONT arial-bold SIZE 12 ANTIALIAS TRUE POSITION CL PARTIALS FALSE MINDISTANCE 300 BUFFER 4 END END Some said adding a "TEXT ([*])" in "LABEL", but I don't know howto? Thanks for your help!

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• What arguments to use to explain why a SQL DB is far better then a flat file

  - by jamone

  The higher ups in my company were told by good friends that flat files are the way to go, and we should switch from MS SQL server to them for everything we do. We have over 300 servers and hundreds of different databases. From just the few I'm involved with we have 10 billion records in quite a few of them with upwards of 100k new records a day and who knows how many updates... Me and a couple others need to come up with a response saying why we shouldn't do this. Most of our stuff is ASP.NET with some legacy ASP. We thought that making a simple console app that tests/times the same interactions between a flat file (stored on the network) and SQL over the network doing large inserts, searches, updates etc along with things like network disconnects randomly. This would show them how bad flat files can be espically when you are dealing with millions of records. What things should I use in my response? What should I do with my demo code to illustrate this? My sort list so far: Security Concurent access Performance with large ammounts of data Ammount of time to do such a massive rewrite/switch Lack of transactions PITA to map relational data to flat files I fear that this will be a great post on the Daily WTF someday if I can't stop it now.

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• How to isolate data per customer, Django powered website

  - by Sawwy

  I have recently started learning python and django and working on a project that includes building a website for collecting information from customers. I am currently trying to figure out best way to isolate the customer data (collected information is sensitive and should only be accessible by customer and the service provider). I found this post Postgresql - one database for everyone, or one-database per customer and my question is that can I automate the model inheritance with customer creation via admin? To be specific, when save() is called for adding customer via django admin, this should create the customer specific tables (create a new set of tables with 'company_name' -prefix). For more information of the environment, I have extended the basic user registration with custom UserProfile adding 'company' and 'role' fields for each user. Upon login, the 'company' of the user will be checked to filter out tables without the 'company_name' prefix. 'Role' will further filter the which company-specific tables and set rights (view, edit). will appreciate any suggestions if more elegant methods could be used to solve the data isolation problem than model inheritance.

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• Should I be concerned about performance with connections to multiple databases?

  - by Josh Ryan

  I have a PHP app that is running on an Apache server with MySQL databases. Based on the subdomain that users access, I am connecting them to a database (sub1.domain.com connects to database_sub1 and sub2.domain.com connects to database_sub2). Right now there are 10 subdomain-database combos, but that number could potentially grow to well over 100. So, is this a bad thing? Considering my situation, is myslq_pconnect a better way to go? Thanks, and please let me know if more info would be helpful. Josh

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• Creating a triple store query using SQL - how to find all triples that have a common predicate and o

  - by Ankur

  I have a database that acts like a triple store, except that it is just a simple MySQL database. I want to select all triples that have a common predicate and object. Info about RDF and triples I can't seem to work out the SQL. If I had just a single predicate and object to match I would do: select TRIPLE from TRIPLES where PREDICATE="predicateName" and OBJECT="objectName" But if I have a list (HashMap) of many pairs of (predicateName,objectName) I am not sure what I need to do. Please let me know if I need to provide more info, I am not sure that I have made this quite clear, but I am wary of providing too much info and confusing the issue.

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• Working with hibernate/DAO problems

  - by Gandalf StormCrow

  Hello everyone here is my DAO class : public class UsersDAO extends HibernateDaoSupport { private static final Log log = LogFactory.getLog(UsersDAO.class); protected void initDao() { //do nothing } public void save(User transientInstance) { log.debug("saving Users instance"); try { getHibernateTemplate().saveOrUpdate(transientInstance); log.debug("save successful"); } catch (RuntimeException re) { log.error("save failed", re); throw re; } } public void update(User transientInstance) { log.debug("updating User instance"); try { getHibernateTemplate().update(transientInstance); log.debug("update successful"); } catch (RuntimeException re) { log.error("update failed", re); throw re; } } public void delete(User persistentInstance) { log.debug("deleting Users instance"); try { getHibernateTemplate().delete(persistentInstance); log.debug("delete successful"); } catch (RuntimeException re) { log.error("delete failed", re); throw re; } } public User findById( java.lang.Integer id) { log.debug("getting Users instance with id: " + id); try { User instance = (User) getHibernateTemplate() .get("project.hibernate.Users", id); return instance; } catch (RuntimeException re) { log.error("get failed", re); throw re; } } } Now I wrote a test class(not a junit test) to test is everything working, my user has these fields in the database : userID which is 5characters long string and unique/primary key, and fields such as address, dob etc(total 15 columns in database table). Now in my test class I intanciated User added the values like : User user = new User; user.setAddress("some address"); and so I did for all 15 fields, than at the end of assigning data to User object I called in DAO to save that to database UsersDao.save(user); and save works just perfectly. My question is how do I update/delete users using the same logic? Fox example I tried this(to delete user from table users): User user = new User; user.setUserID("1s54f"); // which is unique key for users no two keys are the same UsersDao.delete(user); I wanted to delete user with this key but its obviously different can someone explain please how to do these. thank you

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• the MVCC effect on migration from oracle to db2

  - by Ryan Fernandes

  I have a simple (actually simplified :) ) scenario that is possibly the cause for the headache I've been having for the last few days... My current application (that serves 100's of users) currently uses Oracle as the database. I have no stored procs (I wish actually). Now, I've been asked if the product will work if I migrate to IBM DB2 as the database. So, after taking Oracle for granted all this while.... and having re-read Tom's article on MVCC (Multiversion Concurrency Control) and going through this post stating that DB2 is not 'on the list' or 'just tip-toeing in the area' as it were... I know I can't be sure that the product will work with DB2 as is. Is there no hope.. or is there a nice disclaimer I could use.. ?

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• How to consolidate multiple LOG files into one .LDF file in SQL2000

  - by John Galt

  Here is what sp_helpfile says about my current database (recovery model is Simple) in SQL2000: name fileid filename size maxsize growth usage MasterScratchPad_Data 1 C:\SQLDATA\MasterScratchPad_Data.MDF 6041600 KB Unlimited 5120000 KB data only MasterScratchPad_Log 2 C:\SQLDATA\MasterScratchPad_Log.LDF 2111304 KB Unlimited 10% log only MasterScratchPad_X1_Log 3 E:\SQLDATA\MasterScratchPad_X1_Log.LDF 191944 KB Unlimited 10% log only I'm trying to prepare this for a detach then an attach to a sql2008 instance but I don't want to have the 2nd .LDF file (I'd like to have just one file for the log). I have backed up the database. I have issued: BACKUP LOG MasterScratchPad WITH TRUNCATE_ONLY. I have run multiple DBCC SHRINKFILE commands on both of the LOG files. How can I accomplish this goal of having just one .LDF? I cannot find anything on how to delete the one with fileid of 3 and/or how to consolidate multiple files into one log file.

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• Shared Variable Among Ruby Processes

  - by Jesse J

  I have a Ruby program that loads up two very large yaml files, so I can get some speed-up by taking advantage of the multiple cores by forking off some processes. I've tried looking, but I'm having trouble figuring how, or even if, I can share variables in different processes. The following code is what I currently have: @proteins = "" @decoyProteins = "" fork do @proteins = YAML.load_file(database) exit end fork do @decoyProteins = YAML.load_file(database) exit end p @proteins["LVDK"] P displays nil though because of the fork. So is it possible to have the forked processes share the variables? And if so, how?

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• Convert object to DateRange

  - by user655832

  I'm querying an underlying PostgreSQL database using Pandas 0.8. Pandas is returning the DataFrame properly but the underlying timestamp column in my database is being returned as a generic "object" type in Pandas. As I would eventually like to seasonal normalization of my data I am curious as to how to convert this generic "object" column to something that is appropriate for analysis. Here is my current code to retrieve the data: # get records from db example import pandas.io.sql as psql import psycopg2 # define query to get all subs created this year QRY = """ select i i, i * random() f, case when random() > 0.5 then true else false end t, (current_date - (i*random())::int)::timestamp with time zone tsz from generate_series(1,1000) as s(i) order by 4 ; """ CONN_STRING = "host='localhost' port=5432 dbname='postgres' user='postgres'" # connect to db conn = psycopg2.connect(CONN_STRING) # get some data set index on relid column df = psql.frame_query(QRY, con=conn) print "Row count retrieved: %i" % (len(df),) Thanks for any help you can render. M

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• Evaluating Django Chained QuerySets Locally

  - by jnadro52

  Hello All: I am hoping someone can help me out with a quick question I have regarding chaining Django querysets. I am noticing a slow down because I am evaluating many data points in the database to create data trends. I was wondering if there was a way to have the chained filters evaluated locally instead of hitting the database. Here is a (crude) example: pastries = Bakery.objects.filter(productType='pastry') # <--- will obviously always hit DB, when evaluated cannoli = pastries.filter(specificType='cannoli') # <--- can this be evaluated locally instead of hitting the DB when evaluated, as long as pastries was evaluated? I have checked the docs and I do not see anything specifying this, so I guess it's not possible, but I wanted to check with the 'braintrust' first ;-). BTW - I know that I can do this myself by implementing some methods to loop through these datapoints and evaluate the criteria, but there are so many datapoints that my deadline does not permit me manually implementing this. Thanks in advance.

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• How to manipulate a gridview in asp.net when the columns in the gridview are generated during runtim

  - by Nandini

  Hi guys, In my application,i have a gridview in which columns are created at runtime.Actually these columns are created when i am entering data in a database table. My gridview is like this:- Description | Column1 | Column2 | Column3 | ...... |....... |......... Input volt | 55 | 56 | 553 |........ Output volt | 656 | 45 | 67 | where Column1,Column2,column3 may vary during runtime.i need to enter values to these columns during runtime.But i cant bind these columns because these are created during runtime. The first column "Description" will not change.It will remain constant.For each description,there will be values for each column.At last these data will be saved to the database.How to add columns in the gridview during runtime?

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• How do I display a field's hidden characters in the result of a query in Oracle?

  - by Chris Williams

  I have two rows that have a varchar column that are different according to a Java .equals(). I can't easily change or debug the Java code that's running against this particular database but I do have access to do queries directly against the database using SQLDeveloper. The fields look the same to me (they are street addresses with two lines separated by some new line or carriage feed/new line combo). Is there a way to see all of the hidden characters as the result of a query?I'd like to avoid having to use the ascii() function with substr() on each of the rows to figure out which hidden character is different. I'd also accept some query that shows me which character is the first difference between the two fields.

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