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  • How to quickly search through a very large list of strings / records on a database

    - by Giorgio
    I have the following problem: I have a database containing more than 2 million records. Each record has a string field X and I want to display a list of records for which field X contains a certain string. Each record is about 500 bytes in size. To make it more concrete: in the GUI of my application I have a text field where I can enter a string. Above the text field I have a table displaying the (first N, e.g. 100) records that match the string in the text field. When I type or delete one character in the text field, the table content must be updated on the fly. I wonder if there is an efficient way of doing this using appropriate index structures and / or caching. As explained above, I only want to display the first N items that match the query. Therefore, for N small enough, it should not be a big issue loading the matching items from the database. Besides, caching items in main memory can make retrieval faster. I think the main problem is how to find the matching items quickly, given the pattern string. Can I rely on some DBMS facilities, or do I have to build some in-memory index myself? Any ideas? EDIT I have run a first experiment. I have split the records into different text files (at most 200 records per file) and put the files in different directories (I used the content of one data field to determine the directory tree). I end up with about 50000 files in about 40000 directories. I have then run Lucene to index the files. Searching for a string with the Lucene demo program is pretty fast. Splitting and indexing took a few minutes: this is totally acceptable for me because it is a static data set that I want to query. The next step is to integrate Lucene in the main program and use the hits returned by Lucene to load the relevant records into main memory.

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  • How to do integrated testing?

    - by Enthusiastic Programmer
    So I have been reading up on a lot of books surrounding testing. But all the books I've read have the same flaws. They will all tell you the definitions of testing. But I have not found a single book that will guide you into integration testing (or pretty much anything higher then unit testing). Is integration testing that elusive or am I reading the wrong books? I'm a hands on person, so I would appreciate it if someone could help me with a simple program: Let's say you need to make some sort of calculation program that calculates something (doesn't matter what) and exports it to *.txt file. Let's assume we use the Model View Controller design principle. And one class for the actual calculating which you'll use in the model and one for writing the textfile. So: View = Controller = Model = CalculationClass, FileClass So for unittesting: You'd test the calculationClass, I'd personally focus most of my unit tests there. And less time on unit testing the view/controller/FileClass. I personally wouldn't see the use of unittesting those unless you want a really robust program. Integration testing: Now this is where I run into a wall. What would I have to test to call it an integration test? I could stub the view and feed the controller data which it would pass on to the model and so forth. And then check what the view gets back in the end. But ... Couldn't I just run the (in this case small) program then and test it manually? Would this be considered a integration test too, or does it have to be automated? Also, can I check multiple items to see if they are correct? I cannot seem to find any book that offers a hands on approach to methods of integration testing.

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  • Database migrations for SQL Server

    - by Art
    I need a database migration framework for SQL Server, capable of managing both schema changes and data migrations. I guess I am looking for something similar to django's South framework here. Given the fact that South is tightly coupled with django's ORM, and the fact that there's so many ORMs for SQL Server I guess having just a generic migration framework, enabling you to write and execute in controlled and sequential manner SQL data/schema change scripts should be sufficient.

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  • Database migrations for MS SQL Server

    - by Art
    I need a database migration framework for MS SQL Server, capable of managing both schema changes and data migrations. I guess I am looking for something similar to django's South framework here. given the fact that South is tightly coupled with django's ORM, and the fact that there's so many ORMs for MS SQL I guess having just a generic migration framework, enabling you to write and execute in controlled and sequential manner SQL data/schema change scripts should be sufficient. Thanks!

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  • Storing Preferences/One-to-One Relationships in Database

    - by LnDCobra
    What is the best way to store settings for certain objects in my database? Method one: Using a single table Table: Company {CompanyID, CompanyName, AutoEmail, AutoEmailAddress, AutoPrint, AutoPrintPrinter} Method two: Using two tables Table Company {CompanyID, COmpanyName} Table2 CompanySettings{CompanyID, utoEmail, AutoEmailAddress, AutoPrint, AutoPrintPrinter}

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  • What is a columnar database?

    - by Raj More
    I have been working with warehousing for a while now. I am intrigued by Columnar Databases and the speed that they have to offer for data retrievals. I have multi-part question: How do Columnar Databases work? How do they differ from relational databases? Is there a trial version of a columnar database I can install to play around? (I am on Windows 7)

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  • Best books for SQL Server / database design.

    - by ioannis
    I have some really good books for SQL Server, like: SQL Server 2008 Bible Pro SQL Server 2008 - Relational Database Design and Implementation SQL Server 2008 for Developers. Can you suggest/recommend some other titles, that may address other topics perhaps, that you found truly useful?

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  • Database Table of Boolean Values

    - by guazz
    What's the best method of storing a large number of booleans in a database table? Should I create a column for each boolean value or is there a more optimal method? Employee Table IsHardWorking IsEfficient IsCrazy IsOverworked IsUnderpaid ...etc.

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  • Database design for heavy timed data logging

    - by user293995
    Hi, I have an application where I receive each data 40.000 rows. I have 5 million rows to handle (500 Mb MySQL 5.0 database). Actually, thoses rows are stored in the same table = slow to update, hard to backup, ... Which king of scheme is used in such application to allow long term accessibility to the datas without problems with too big tables, easy backup, fast read / write ? Is postgresql better than mysql for such purpose ? Thanks in advance BEst regards

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  • Good tool to visualise database schema?

    - by Mat
    Are there any good tools for visualising a pre-existing database schema? I'm using MySQL if it matters. I'm currently using MySQL Workbench to process an SQL create script dump, but it's clunky, slow and a manual process to drag all the tables about (which would be okay if it wasn't so slow).

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  • internal implementation of database Queries

    - by harigm
    In my experience I have used many queries like select, order by, where clause etc.. in mysql, sql-server, oracle etc For a moment i have thought, 1)how is this internally written to implement the above queries 2) which language do they use? 3) is that programming language? if yes which language? 4)what kind of environment required to implement this kind of complex database

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  • MultiOS "Jet Database" for C++/Qt?

    - by Airjoe
    Hopefully I can articulate this well: I'm porting an application I made years ago from VB6 (I know, I know!) to C++/Qt. In my original application, one thing I liked was that I didn't need an actual SQL server running, I could just use MS Access .mdb files. I was wondering if something similar exists for Qt that will work on multiple OSes - a database stored in a file, pretty much, but that I can still run SQL queries with. Not sure if something like this exists or not, but any help appreciated, thanks!

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  • (database design):Which tables should be created for all kindes files (images, attached email files,

    - by meyosef
    Hi, I new in database design: I have question with my own few solution,what do you thinks?: Which tables should be created for all kinds files (images, attached email files,text files for store email body, etc..) that stored in my online store? *option 1:use seperate table for files types * files{ id files_types_id FK file_path file_extension } files_types{ id type_name (unique) } *option 2: use bool field for each file type * files{ id file_path file_extension is_image_main is_image_icon is_image_logo is_pdf_file is_text_file } **option 3: use 1 enum field 'file_type' for each file type ** files{ id file_path file_extension file_type (image_main,image_icon,image_logo,image_main,pdf,text) **enum** } Thanks you, Yosef

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  • Database Owner Conundrum

    - by Johnm
    Have you ever restored a database from a production environment on Server A into a development environment on Server B and had some items, such as Service Broker, mysteriously cease functioning? You might want to consider reviewing the database owner property of the database. The Scenario Recently, I was developing some messaging functionality that utilized the Service Broker feature of SQL Server in a development environment. Within the instance of the development environment resided two databases: One was a restored version of a production database that we will call "RestoreDB". The second database was a brand new database that has yet to exist in the production environment that we will call "DevDB". The goal is to setup a communication path between RestoreDB and DevDB that will later be implemented into the production database. After implementing all of the Service Broker objects that are required to communicate within a database as well as between two databases on the same instance I found myself a bit confounded. My testing was showing that the communication was successful when it was occurring internally within DevDB; but the communication between RestoreDB and DevDB did not appear to be working. Profiler to the rescue After carefully reviewing my code for any misspellings, missing commas or any other minor items that might be a syntactical cause of failure, I decided to launch Profiler to aid in the troubleshooting. After simulating the cross database messaging, I noticed the following error appearing in Profiler: An exception occurred while enqueueing a message in the target queue. Error: 33009, State: 2. The database owner SID recorded in the master database differs from the database owner SID recorded in database '[Database Name Here]'. You should correct this situation by resetting the owner of database '[Database Name Here]' using the ALTER AUTHORIZATION statement. Now, this error message is a helpful one. Not only does it identify the issue in plain language, it also provides a potential solution. An execution of the following query that utilizes the catalog view sys.transmission_queue revealed the same error message for each communication attempt: SELECT     * FROM        sys.transmission_queue; Seeing the situation as a learning opportunity I dove a bit deeper. Reviewing the database properties  The owner of a specific database can be easily viewed by right-clicking the database in SQL Server Management Studio and selecting the "properties" option. The owner is listed on the "General" page of the properties screen. In my scenario, the database in the production server was created by Frank the DBA; therefore his server login appeared as the owner: "ServerName\Frank". While this is interesting information, it certainly doesn't tell me much in regard to the SID (security identifier) and its existence, or lack thereof, in the master database as the error suggested. I pulled together the following query to gather more interesting information: SELECT     a.name     , a.owner_sid     , b.sid     , b.name     , b.type_desc FROM        master.sys.databases a     LEFT OUTER JOIN master.sys.server_principals b         ON a.owner_sid = b.sid WHERE     a.name not in ('master','tempdb','model','msdb'); This query also helped identify how many other user databases in the instance were experiencing the same issue. In this scenario, I saw that there were no matching SIDs in server_principals to the owner SID for my database. What login should be used as the database owner instead of Frank's? The system stored procedure sp_helplogins will provide a list of the valid logins that can be used. Here is an example of its use, revealing all available logins: EXEC sp_helplogins;  Fixing a hole The error message stated that the recommended solution was to execute the ALTER AUTHORIZATION statement. The full statement for this scenario would appear as follows: ALTER AUTHORIZATION ON DATABASE:: [Database Name Here] TO [Login Name]; Another option is to execute the following statement using the sp_changedbowner system stored procedure; but please keep in mind that this stored procedure has been deprecated and will likely disappear in future versions of SQL Server: EXEC dbo.sp_changedbowner @loginname = [Login Name]; .And They Lived Happily Ever After Upon changing the database owner to an existing login and simulating the inner and cross database messaging the errors have ceased. More importantly, all messages sent through this feature now successfully complete their journey. I have added the ownership change to my restoration script for the development environment.

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  • Database - Designing an "Events" Table

    - by Alix Axel
    After reading the tips from this great Nettuts+ article I've come up with a table schema that would separate highly volatile data from other tables subjected to heavy reads and at the same time lower the number of tables needed in the whole database schema, however I'm not sure if this is a good idea since it doesn't follow the rules of normalization and I would like to hear your advice, here is the general idea: I've four types of users modeled in a Class Table Inheritance structure, in the main "user" table I store data common to all the users (id, username, password, several flags, ...) along with some TIMESTAMP fields (date_created, date_updated, date_activated, date_lastLogin, ...). To quote the tip #16 from the Nettuts+ article mentioned above: Example 2: You have a “last_login” field in your table. It updates every time a user logs in to the website. But every update on a table causes the query cache for that table to be flushed. You can put that field into another table to keep updates to your users table to a minimum. Now it gets even trickier, I need to keep track of some user statistics like how many unique times a user profile was seen how many unique times a ad from a specific type of user was clicked how many unique times a post from a specific type of user was seen and so on... In my fully normalized database this adds up to about 8 to 10 additional tables, it's not a lot but I would like to keep things simple if I could, so I've come up with the following "events" table: |------|----------------|----------------|--------------|-----------| | ID | TABLE | EVENT | DATE | IP | |------|----------------|----------------|--------------|-----------| | 1 | user | login | 201004190030 | 127.0.0.1 | |------|----------------|----------------|--------------|-----------| | 1 | user | login | 201004190230 | 127.0.0.1 | |------|----------------|----------------|--------------|-----------| | 2 | user | created | 201004190031 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 2 | user | activated | 201004190234 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 2 | user | approved | 201004190930 | 217.0.0.1 | |------|----------------|----------------|--------------|-----------| | 2 | user | login | 201004191200 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | created | 201004191230 | 127.0.0.1 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | impressed | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 2 | user | blocked | 201004200319 | 217.0.0.1 | |------|----------------|----------------|--------------|-----------| | 2 | user | deleted | 201004200320 | 217.0.0.1 | |------|----------------|----------------|--------------|-----------| Basically the ID refers to the primary key (id) field in the TABLE table, I believe the rest should be pretty straightforward. One thing that I've come to like in this design is that I can keep track of all the user logins instead of just the last one, and thus generate some interesting metrics with that data. Due to the nature of the events table I also thought of making some optimizations, such as: #9: Since there is only a finite number of tables and a finite (and predetermined) number of events, the TABLE and EVENTS columns could be setup as ENUMs instead of VARCHARs to save some space. #14: Store IPs as UNSIGNED INT with INET_ATON() instead of VARCHARs. Store DATEs as TIMESTAMPs instead of DATETIMEs. Use the ARCHIVE (or the CSV?) engine instead of InnoDB / MyISAM. Overall, each event would only consume 14 bytes which is okay for my traffic I guess. Pros: Ability to store more detailed data (such as logins). No need to design (and code for) almost a dozen additional tables (dates and statistics). Reduces a few columns per table and keeps volatile data separated. Cons: Non-relational (still not as bad as EAV): SELECT * FROM events WHERE id = 2 AND table = 'user' ORDER BY date DESC(); 6 bytes overhead per event (ID, TABLE and EVENT). I'm more inclined to go with this approach since the pros seem to far outweigh the cons, but I'm still a little bit reluctant.. Am I missing something? What are your thoughts on this? Thanks!

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  • Virtualbox HTTP load testing, host CPU overload issues

    - by aschuler
    I'm doing HTTP load testing benchmarks (using Apache Benchmark and Siege) on a small Java EE 1.7.0 / Tomcat 7.0.26 application running on a Debian Squeeze 6.0.4 x64 virtualized with Virtualbox 4.1.8. The computer host is Ubuntu 11.10 x64. I've modified those parameters in the Tomcat server.xml : <Connector port="8080" protocol="HTTP/1.1" connectionTimeout="200000" redirectPort="8443" acceptCount="2000" maxThreads="150" minSpareThreads="50" /> The application executed on the server takes around 300ms. This app is running well until a certain amount of concurrent connections like those one : ab -n 500 -c 150 http://xx.xx.xx.xx:8080/myapp/ ab -n 1000 -c 50 http://xx.xx.xx.xx:8080/myapp/ siege -b -c 100 -r 20 http://xx.xx.xx.xx:8080/myapp/ A lot of socket connection timed out happens and this completly overload the host processor (but the CPU load inside the VM is normal). Doing an htop on the host, i can see that the Virtualbox processus is running under 300% CPU and never come down even after the load test is finished. (I've allocated 4 processors to the VM, if I allocate only one processor, CPU load goes under 100%). Restarting Tomcat don't do anything, i'm forced to restart the whole VM. I've tryed to launch those ab/siege commands locally on the VM and everything goes well. I first thought it was related to a linux network limit as explained here: Running some benchmarks using ab, and tomcat starts to really slow down So I've modified those TCP parameters : echo 15 > /proc/sys/net/ipv4/tcp_fin_timeout echo 30 > /proc/sys/net/ipv4/tcp_keepalive_intvl echo 1 > /proc/sys/net/ipv4/tcp_tw_recycle echo 1 > /proc/sys/net/ipv4/tcp_tw_reuse It seems to be better, but it continues to overload the host CPU and output socket connections time out at a certain amount of concurrent connections. I'm wondering if this is not related to how Virtualbox handles external concurrent connections.

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  • Load Testing a Security/Gateway Appliance

    - by Joel Coel
    In a couple weeks I will load testing a security/gateway appliance. We're a small residential college, and that "residential" means the traffic moving through the appliance is a bit like the Wild West. We have everything from Facebook to World of Warcraft, BitTorrent to Netflix, or Halo to YouTube... basically anything you might find in the home of a high-school or college aged person. Somewhere in there some real academic work gets done as well. We rely on our current appliance for traffic shaping, antivirus, malware filtering, intrusion detection on our servers, logging and abuse reporting, and even some content filtering. All this puts a decent load when we have students around, and I'm concerned about the ability of the new candidate to keep up. On paper it should handle things, but I'm worried. Prior experience is that vendors greatly over-report what an appliance can handle. The product also includes a licensed session limit, and I'm also worried that just a few misbehaving students could unwittingly bring us to that limit and cause service disruptions. I need to know this will work for our campus in order to commit to it. Going a performance level higher in that product takes the pricing way out of line with what we expect and have done in the past. What I need is a good way to load test this guy. My problem is that our current level of summer traffic is less than one percent of what it will be when students come back just six weeks from now. Any ideas on how to really stress this thing and see what it can do, in a way that will give me some clear ideas o. How that will scale for our campus? For the curious, I'm looking at a Watchguard 515, but it could be anything. If I were evaluating a competitor, I'd ask the same question.

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  • Ha a hutés nem elég a gépteremben: Sun Cooling Door a Database Machine-hoz

    - by Fekete Zoltán
    A Database Machine hatalmas teljesítménye miatt általában jóval kevesebb hutésre van szükség, mintha egy külön high-end servert és külön high-end storage-ot hutenénk! Ha viszont a géptermünk maradék hutési kapacitása nem elegendo, és nem elégszünk meg a "hagyományos mosóporral", akkor újabb hutési trükkre van szükség. Erre kínálnak megoldást a Sun Cooling Door modellek, például az 5200-as és az 5600-as modellek.

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  • Adatlap az Exadata, Database Machine supporthoz

    - by Fekete Zoltán
    Letöltheto és megtekintheto, sot elolvasható :) a COMPLETE SUPPORT SERVICES FOR ORACLE EXADATA dokumentum, amely részletesen leírja, milyen trméktámogatási lehetoségeket lehet igénybe venni egy Database Machine megoldáshoz. Az Exadata termékcsalád elemei mind tranzakciós rendszerek mind adattárházak adatbázisának futtatásához és adatbázisok egy közös szerveren muködtetéséhez nyújtanak optimális, nagy teljesítményu platformot.

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