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  • Embeddable database better than SQLite for java

    - by dexter
    I am creating a web application that is accessing a SQLite database in the server. I also have "clients" that updates this same database. As we know SQLite locks the entire database during INSERTs which are done by the clients and the web application is also trying to make some UPDATEs at the same time. So my problem now is about concurrency in database access. I would like to use an embeddable database like SQLite. Any suggestions.

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  • Need some clarification on the ANSI/SPARC 3-tier database architecture.

    - by Moonshield
    Hi there, I'm currently revising for a databases exam and looking over some past papers, but there's one question that I'm slightly unsure about and was wondering if someone could offer some assistance. "Describe EACH of the THREE levels of the ANSI SPARC 3 level architecture. Your answer should include the purpose of EACH of the schemas, the level of abstraction they provide and the software tools that would be used to access and support them." As I understand it (although please correct me if I'm wrong): the internal schema specifies the physical storage of the data; the conceptual schema specifies the structure of the database and the domains; and the external schemas are how the database is viewed by "users" (applications, etc.). As for the abstraction, I understand that the conceptual layer means that the physical data storage can be altered without the end user being affected, likewise the The bit that I'm not sure about is what tools are used to access and support each layer. Would the internal schema be handled by the DBMS, the conceptual schema handled by some sort of DDL interpreter and the external schema handled by a DML interpreter (or have I misunderstood what each level does)? Any assistance would be greatly appreciated. Thanks, Moonshield

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  • Chicken and egg problem (restore database) when trying to write unit test against SQl Server 2008.

    - by Hamish Grubijan
    Ok, they are not unit tests but end-to-end tests. The setup is somewhat involved. Unit tests will use C#, ODBC connection. Every unit tests will try to clean up after itself, but every 20 tests or so (once per C# class) we would need to do a full database restore. I do not think I can do it over an ODBC connection, according to this document: http://www.sql-server-performance.com/articles/dba/Obtain_Exclusive_Access_to_Restore_SQL_Server_p1.aspx Msg 6104, Level 16, State 1, Line 1 Cannot use KILL to kill your own process. However, I would like to, so that 199 tests do not go amok because of a bad clean-up. Is there another way? Perhaps I can open a different "connection" such as use COM automation or something of that sort, and then kill all database connections from there? If so, how can I do that? Also, will the clients be able to re-connect automatically after a restore, or would I have to dismantle everything once every 20 tests or so? If you find this question confusing, please let me know what your questions are. Thanks!

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  • How do find the longest path in a cyclic Graph between two nodes?

    - by Nazgulled
    Hi, I already solved most the questions posted here, all but the longest path one. I've read the Wikipedia article about longest paths and it seems any easy problem if the graph was acyclic, which mine is not. How do I solve the problem then? Brute force, by checking all possible paths? How do I even begin to do that? I know it's going to take A LOT on a Graph with ~18000. But I just want to develop it anyway, cause it's required for the project and I'll just test it and show it to the instructor on a smaller scale graph where the execution time is just a second or two. At least I did all tasks required and I have a running proof of concept that it works but there's no better way on cyclic graphs. But I don't have clue where to start checking all these paths...

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  • Spring Roo Database Reverse Engineer with Oracle

    - by kerry
    So you are trying to reverse engineer an Oracle database with roo? Unfortunately, due to licensing restrictions with the Oracle JDBC Drivers, this is a little difficult. There are a few blog posts and forum threads that address the problem but I figured I would post what worked for me here. First, you need to download the appropriate Oracle Drivers from Oracle. The required login, stringent password requirements, nosy registration form, and general system instability made this a pretty painful step for me. I’d also like to say that companies that have password requirements that don’t allow symbols (or any other non-standard requirement) have a special place in my heart. Having to recover my password every time I go to your site virtually guarantees I will only go there when I absolutely have to (not often). Anyways, once you have it downloaded you need to install is with maven: mvn install:install-file -Dfile=~/Downloads/ojdbc6.jar -DgroupId=com.oracle -DartifactId=ojdbc6 -Dversion=11.2.0.3 -Dpackaging=jar -DgeneratePom=true Here comes the fun part. You need to create an osgi wrapper for the driver to install it in roo. Otherwise, roo cannot see the driver. Create a new folder and put the contents of the oracle roo addon pom gist I created. Now build it with maven. You may want to change some of the artifact ids and dependencies for your particular situation. mvn package No open a roo shell and execute the following command: osgi install --url file:///Users/me/my-osgi-project/target/the-jar-it-built.jar Now run (in roo): jpa setup --provider HIBERNATE --database ORACLE dependency remove --groupId com.oracle --artifactId ojdbc14 --version 10.2.0.2 dependency add --groupId com.oracle --artifactId ojdbc6 --version 11.2.0.3 database properties set --key database.driverClassName --value oracle.jdbc.OracleDriver database properties set --key database.url --value jdbc:oracle:thin:@%YOUR_CONNECTION_INFO% database properties set --key database.username --value %YOUR_USERNAME% database properties set --key database.password --value %YOUR_PASSWORD% database reverse engineer --schema %YOUR_SCHEMA% --package ~.domain If you have any package loading exceptions when running the reverse engineer command you can uninstall the osgi bundle, set the package to optional in the osgi pom in the IncludedPackages tag (javax.some.package.*;resolution:=optional) rebuild, then reinstall in roo.

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  • Neo4j Performing shortest path calculations on stored data

    - by paddydub
    I would like to store the following graph data in the database, graph.makeEdge( "s", "c", "cost", (double) 7 ); graph.makeEdge( "c", "e", "cost", (double) 7 ); graph.makeEdge( "s", "a", "cost", (double) 2 ); graph.makeEdge( "a", "b", "cost", (double) 7 ); graph.makeEdge( "b", "e", "cost", (double) 2 ); Then run the Dijskra algorighm from a web servlet, to find shortest path calculations using the stored graph data. Then I will print the path to a html file from the servlet. Dijkstra<Double> dijkstra = getDijkstra( graph, 0.0, "s", "e" );

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  • Location tagging facebook open graph actions so that only friends in that location view in their feeds

    - by Arvind Srinivasan
    Is there a way to tag open graph actions so as to target certain recipients and not others? For example, if my app talks about new coffee shop openings in various cities, is there a way to publish the 'opening' action to the graph, perhaps with location / coordinates, such that this is only seen by friends in that locality? I really don't want to spam my friends in London about an opening I'm excited about in Portland. How can I help facebook with the feed relevance in these cases? I noticed that there is a "place" property on open graph objects - could this somehow be used?

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  • In a graph, how to find the nearest node to a group of nodes?

    - by Nikola
    Hello, I have an undirected, unweighted graph, which doesn't have to be planar. I also have a subset of graph's nodes (true subset) and I need to find a node not belonging to the subset, with minimum sum of distances to all nodes in the subset. So far, I have implemented breath-first search starting from each node in the subset, and the intersection that occurs first is the node I am looking for. Unfortunately, it is running too slow since the graph contains a large number of nodes. Any advice or comment will be appreciated. Thank you, Nikola

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  • How to detect if breaking an edge will make a graph disjoint?

    - by the_graph_guy
    I have a graph that starts off with a single, root node. Nodes are added one by one to the graph. At node creation time, they have to be linked either to the root node, or to another node, by a single edge. Edges can also be created and deleted (one by one, between any two nodes). Nodes can be deleted one at a time. Node and edge creation, deletion operations can happen in any arbitrary order. OK, so here's my question: When an edge is deleted, is it possible do determine, in constant time (i.e. with an O(1) algorithm), if doing this will divide the graph into two disjoint subgraphs? If it will, then which side of the edge will the root node belong? I'm willing to maintain, within reasonable limits, any additional data structure that can facilitate the derivation of this information. Maybe it is not possible to do it in O(1), if so any pointers to literature will be appreciated.

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  • Storing changes to multiple databases in a single centralized database

    - by B4x
    The setup: multiple MySQL databases at different locations with the same scheme. The databases are in production. The motivation: we want to present information in these databases in a web interface, clearly showing which database the row originated from. We want to be able to get this data from one single source (for different reasons, one of them is pagination which gets tricky if you use multiple sources). The problem: how do we collect data from multiple databases, storing it at a central location and clearly marking the origin of each row? We have discussed using a centralized DB that tracks changes to the production DBs, with the same schema and one additional column for origin. If possible, we would like to avoid having to make changes in the production environment. Since we can't use MySQL's replication (multiple masters to a single slave isn't allowed), what are our other options? Are there any existing solutions for something like this or do we have to code something ourselves? Is the best solution to change the database schemas in production and add a column for origin? The idea of a centralized database isn't set in stone. If there is a solution to this that solves our other problems without a centralized DB, we can be flexible. Any help is much appreciated.

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  • WPF application with MS Access database as a data source

    - by Kay Zed
    I have a Microsoft Access 2010 database. Now, using Visual Studio 2010, I want to create a WPF application and add the database as a data source. The app will have a window with a frame that provides navigation through pages. No problem so far. But: -What is the right way to set up the database in this scenario? Tables only? Or must everything go via queries? (VS2010 talks about views which I assume (?) are queries) -Database data must be updatable and records can be added. Some relationships go through link tables (many-to-many) and there are nullable foreign key relationships. Must I take manual steps to make it work? -While adding the data source VS2010 created an xsd from my Access database. I think the xsd might need further tweaking for the application to work the right way. What if I change my Access database design, I'd have to regenerate the xsd again as well. Is this right, and is it the way it is usually done? OR, should I let the original Access database go and give the application the capability to create new empty databases? -How do you provide controls in a page to step through the records in a table? Is there a special database control? -What is the way (WPF class?) to load records into the data context that displays in a page? (At this level it probably does not matter what type of data source it is.)

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  • SMO restore of SQL database doesn't overwrite

    - by Tom H.
    I'm trying to restore a database from a backup file using SMO. If the database does not already exist then it works fine. However, if the database already exists then I get no errors, but the database is not overwritten. The "restore" process still takes just as long, so it looks like it's working and doing a restore, but in the end the database has not changed. I'm doing this in Powershell using SMO. The code is a bit long, but I've included it below. You'll notice that I do set $restore.ReplaceDatabase = $true. Also, I use a try-catch block and report on any errors (I hope), but none are returned. Any obvious mistakes? Is it possible that I'm not reporting some error and it's being hidden from me? Thanks for any help or advice that you can give! function Invoke-SqlRestore { param( [string]$backup_file_name, [string]$server_name, [string]$database_name, [switch]$norecovery=$false ) # Get a new connection to the server [Microsoft.SqlServer.Management.Smo.Server]$server = New-SMOconnection -server_name $server_name Write-Host "Starting restore to $database_name on $server_name." Try { $backup_device = New-Object("Microsoft.SqlServer.Management.Smo.BackupDeviceItem") ($backup_file_name, "File") # Get local paths to the Database and Log file locations If ($server.Settings.DefaultFile.Length -eq 0) {$database_path = $server.Information.MasterDBPath } Else { $database_path = $server.Settings.DefaultFile} If ($server.Settings.DefaultLog.Length -eq 0 ) {$database_log_path = $server.Information.MasterDBLogPath } Else { $database_log_path = $server.Settings.DefaultLog} # Load up the Restore object settings $restore = New-Object Microsoft.SqlServer.Management.Smo.Restore $restore.Action = 'Database' $restore.Database = $database_name $restore.ReplaceDatabase = $true if ($norecovery.IsPresent) { $restore.NoRecovery = $true } Else { $restore.Norecovery = $false } $restore.Devices.Add($backup_device) # Get information from the backup file $restore_details = $restore.ReadBackupHeader($server) $data_files = $restore.ReadFileList($server) # Restore all backup files ForEach ($data_row in $data_files) { $logical_name = $data_row.LogicalName $physical_name = Get-FileName -path $data_row.PhysicalName $restore_data = New-Object("Microsoft.SqlServer.Management.Smo.RelocateFile") $restore_data.LogicalFileName = $logical_name if ($data_row.Type -eq "D") { # Restore Data file $restore_data.PhysicalFileName = $database_path + "\" + $physical_name } Else { # Restore Log file $restore_data.PhysicalFileName = $database_log_path + "\" + $physical_name } [Void]$restore.RelocateFiles.Add($restore_data) } $restore.SqlRestore($server) # If there are two files, assume the next is a Log if ($restore_details.Rows.Count -gt 1) { $restore.Action = [Microsoft.SqlServer.Management.Smo.RestoreActionType]::Log $restore.FileNumber = 2 $restore.SqlRestore($server) } } Catch { $ex = $_.Exception Write-Output $ex.message $ex = $ex.InnerException while ($ex.InnerException) { Write-Output $ex.InnerException.message $ex = $ex.InnerException } Throw $ex } Finally { $server.ConnectionContext.Disconnect() } Write-Host "Restore ended without any errors." }

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  • Database structure and source control - best practice

    - by Paddy
    Background I came from several years working in a company where all the database objects were stored in source control, one file per object. We had a list of all the objects that was maintained when new items were added (to allow us to have scripts run in order and handle dependencies) and a VB script that ran to create one big script for running against the database. All the tables were 'create if not exists' and all the SP's etc. were drop and recreate. Up to the present and I am now working in a place where the database is the master and there is no source control for DB objects, but we do use redgate's tools for updating our production database (SQL compare), which is very handy, and requires little work. Question How do you handle your DB objects? I like to have them under source control (and, as we're using GIT, I'd like to be able to handle merge conflicts in the scripts, rather than the DB), but I'm going to be pressed to get past the ease of using SQL compare to update the database. I don't really want to have us updating scripts in GIT and then using SQL compare to update the production database from our DEV DB, as I'd rather have 'one version of the truth', but I don't really want to get into re-writing a custom bit of software to bundle the whole lot of scripts together. I think that visual studio database edition may do something similar to this, but I'm not sure if we will have the budget for it. I'm sure that this has been asked to death, but I can't find anything that seems to quite have the answer I'm looking for. Similar to this, but not quite the same: http://stackoverflow.com/questions/340614/what-are-the-best-practices-for-database-scripts-under-code-control

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  • Which Database to choose?

    - by Sundar
    I have the following criteria Database should be protected with a username and password. It should not be possible to copy the database file and use it else were like MS Access. There will be no central database server. Each machine will run their own database server locally and user will initiate synchronization. Concept is inspired from distributed version control system like Git. So it should have good replication support. Strong consistency is not needed. Users will synchronize each other database when they need. In case of conflicts it should be possible to find the conflict and present it (from application) to the user for fixing it. Revisions of data if available it will be good. e.g. Entire history of change to a invoice. I explored document oriented database and inclined towards the same. But I dont know what to choose. Database is small it will not reach even 1GB in the next few years (say 3 years). Please feel free to suggest any database which you think might be suitable. Any pointers is highly appreciated. Thanks in advance.

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  • How to configure database connection securely

    - by chiccodoro
    Similar but not the same: How to securely store database connection details Securely connecting to database within a application Hi all, I have a C# WinForms application connecting to a database server. The database connection string, including a generic user/pass, is placed in a NHibernate configuration file, which lies in the same directory as the exe file. Now I have this issue: The user that runs the application should not get to know the username/password of the general database user because I don't want him to rummage around in the database directly. Alternatively I could hardcode the connection string, which is bad because the administrator must be able to change it if the database is moved or if he wants to switch between dev/test/prod environments. So long I've found three possibilities: The first referenced question was generally answered by making the file only readable for the user that runs the application. But that's not not enough in my case (the user running the application is a person. The database user/pass are general and shouldn't even be accessible by the person.) The first answer additionally proposed to encrypt the connection data before writing it to the file. With this approach, the administrator is not able anymore to configure the connection string because he cannot encrypt it by hand. The second referenced question provides an approach for this very scenario but it seems very complicated. My questions to you: This is a very general issue, so isn't there any general "how-to-do-it" way, somehow a "design pattern"? Is there some support in .NET's config infrastructure? (optional, maybe out of scope) Can I combine that easily with the NHibernate configuration mechanism?

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  • Database for Python Twisted

    - by Will
    There's an API for Twisted apps to talk to a database in a scalable way: twisted.enterprise.dbapi The confusing thing is, which database to pick? The database will have a Twisted app that is mostly making inserts and updates and relatively few selects, and then other strictly-read-only clients that are accessing the database directly making selects. (The read-only users are not necessarily selecting the data that the Twisted app is inserting; its not as though the database is being used as a message-queue) My understanding - which I'd like corrected/adviced - is that: Postgres is a great DB, but all the Python bindings - and there is a confusing maze of them - are abandonware There is psycopg2, but that makes a lot of noise about doing its own connection-pooling and things; does this co-exist gracefully/usefully/transparently with the Twisted async database connection pooling and such? SQLLite is a great database for little things but if used in a multi-user way it does whole-database locking, so performance would suck in the usage pattern I envisage MySQL - after the Oracle takeover, who'd want to adopt it now or adopt a fork? Is there anything else out there?

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  • SQL Server Database In Single User Mode after Failover

    - by jlichauc
    Here is a weird situation we experienced with a SQL Server 2008 Database Mirroring Failover. We have a pair of mirrored databases running in high-availability mode and both the principal and mirror showed as synchronized. As part of some maintenance I triggered a manual failover of the principal to the mirror. However after the failover the principal was now in single-user mode instead of the expected "Principal/Synchronized" state we usually get. The database had been in multi-user mode on the previous principal before this had happened. We ended up stopping all applications, restarting the SQL Server instances, and executing "ALTER DATABASE ... SET MULTI_USER" to bring the database back to the expected "Principal/Synchronized" state in a multi-user mode. Question. Does anyone know where SQL Server stores information about whether a database should be in single-user mode or not? I'm wondering if there is some system database or table that has this setting recorded somewhere. In particular we had an incident once with the database on the original principal (the one I was failing over to) where when trying to detach the database it was put into single-user mode. I'm wondering if that setting is cached somewhere and is the reason that SQL Server put it back into single-user mode after a failover.

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  • how do i implement / build / create an 'in memory database' for my unit test

    - by Michel
    Hi all, i've started unit testing a while ago and as turned out i did more regression testing than unit testing because i also included my database layer thus going to the database verytime. So, implemented Unity to inject a fake database layer, but i of course want to store some data, and the main opinion was: "create an in-memory database" But what is that / how do i implement that? Main question is: i think i have to fake the database layer, but doesn't that make me create a 'simple database' myself or: how can i keep it simple and not rebuilding Sql Server just for my unit tests :) At the end of this question i'll give an explanation of the situation i got in on the project i just started on, and i was wondering if this was the way to go. Michel Current situation i've seen at this client is that testdata is contained in XML files, and there is a 'fake' database layer that connects all the xml files together. For the real database we're using the entity framework, and this works very simple. And now, in the 'fake' layer, i have top create all kind of classes to load, save, persist etc. the data. It sounds weird that there is so much work in the fake layer, and so little in the real layer. I hope this all makes sense :)

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  • How to optimize paging for large in memory database

    - by snakefoot
    I have an application where the entire database is implemented in memory using a stl-map for each table in the database. Each item in the stl-map is a complex object with references to other items in the other stl-maps. The application works with a large amount of data, so it uses more than 500 MByte RAM. Clients are able to contact the application and get a filtered version of the entire database. This is done by running through the entire database, and finding items relevant for the client. When the application have been running for an hour or so, then Windows 2003 SP2 starts to page out parts of the RAM for the application (Eventhough there is 16 GByte RAM on the machine). After the application have been partly paged out then a client logon takes a long time (10 mins) because it now generates a page fault for each pointer lookup in the stl-map. I can see it is possible to tell Windows to lock memory in RAM, but this is generally only recommended for device drivers, and only for "small" amounts of memory. I guess a poor mans solution could be to loop through the entire memory database, and thus tell Windows we are still interested in keeping the datamodel in RAM. I guess another poor mans solution could be to disable the pagefile completely on Windows. I guess the expensive solution would be a SQL database, and then rewrite the entire application to use a database layer. Then hopefully the database system will have implemented means to for fast access. Are there other more elegant solutions ?

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  • Partner Webcast – More out of ODA with DB Options - 19 July 2012

    - by Thanos
    The Simple, Reliable, Affordable Path to High-Availability Databases Critical business data needs to be available 24/7 for users and customers, but it can be a struggle to find the time and resources to build a highly available database system that’s reliable and affordable. That’s why Oracle created the new Oracle Database Appliance—a complete package of software, server, storage, and networking. The Oracle Database Appliance integrates the world’s most popular database - Oracle Database 11g  - with system software, servers, storage and networking in a single box. Business gets the benefit of a reliable, secure and highly available database to support applications and maintain continuity – as well as groundbreaking ease of use. But that is not all, with the support for all Oracle Database Options, Oracle Database Appliance can be the ideal solution for many use cases. The benefits?   Unmatched performance, reliability & security for your data that’s there when you need it – which is all the time. Fast installation, simple deployment, easy management. Out of the box. Significant cost savings & reduced risk and complexity compared to integrating all the elements yourself. Ongoing lower total cost of ownership with multiple automated support, detection & correction functions that also save you time.   Discover the Oracle Database Appliance Value Proposition and learn how to position and combine it with database options to capture new business and easily roll out solutions safely and with maximum cost efficiency. Agenda: Oracle Database& Engineered Systems Innovation. What’s the Oracle Database Appliance ? Oracle Database Appliance Value Proposition. Oracle Database Appliance with Database Options Oracle Database Appliance Partners Business Delivery Format This FREE online LIVE eSeminar will be delivered over the Web. Registrations received less than 24hours prior to start time may not receive confirmation to attend. Duration: 1 hour Register Now! For any questions please contact us at partner.imc-AT-beehiveonline.oracle-DOT-com Visit regularly our ISV Migration Center blog Or Follow us @oracleimc to learn more on Oracle Technologies as well as upcoming partner webcasts and events.

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  • Google Analytics show zero for "Search Engine Optimizations" graph

    - by Saeed Neamati
    In Google Analytics new design, there is an area related to the queries and impressions related to your site. You can get there by following Traffic Sources = Search Engine Optimization = Queries. However, it now shows zero for the "Site Usage" graph, at the top section, while other areas of Google Analytics definitely show that site has visitors and has been used. No matter how much I search, I can't find the source of the problem. Does anyone know where the problem might be?

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  • Is it possible to write a database view that encompasses one-to-many relationships?

    - by Brandon Linton
    So I'm not necessarily saying this is even a good idea if it were possible, since the schema of the view would be extremely volatile, but is there any way to represent a has-many relationship in a single view? For example, let's say I have a customer that can have any number of addresses in the database. Is there any way to list out each column of each address with perhaps a number as a part of the alias (e.g., columns like Customer Id, Name, Address_Street_1, Address_Street_2, etc)? Thanks!

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