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  • Scalability comparison between different DBMSs

    - by Björn Lindfors
    By what factor does the performance (read queries/sec) increase when a machine is added to a cluster of machines running either: a Bigtable-like database MySQL? Google's research paper on Bigtable suggests that "near-linear" scaling is achieved can be achieved with Bigtable. This page here featuring MySQL's marketing jargon suggests that MySQL is capable of scaling linearly. Where is the truth?

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  • Getting clusters of rows close together in time

    - by Mike
    I have a table basically like so ID | ItemID | Start | End | --------------------------------------------------------------- 1 234 10/20/09 8:34:22 10/20/09 8:35:10 2 274 10/20/09 8:35:30 10/20/09 8:36:27 3 272 10/21/09 12:15:00 10/21/09 12:17:00 4 112 10/21/09 12:20:14 10/21/09 12:21:21 5 15 10/21/09 12:22:39 10/21/09 12:24:15 There are two "clusters" of entries here, 1-2 and 3-5 separated by a gap in time, specifically 30 minutes is what I'm interested in. What I would like is the first and last rows of the cluster of entries. This is fairly easy to achieve by retrieving all the rows and looping through them in order of start time, but I'd like to have it in SQL if possible. I'm using SQL Server 2008, thanks.

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  • MongoDB - proper use of collections?

    - by zmg
    In Mongo my understanding is that you can have databases and collections. I'm working on a social-type app that will have blogs and comments (among other things) and had previously be using MySQL and pretty heavy partitioning in an attempt to limit possible concurrency issues. With MySQL I've stuffed all my user data into a _user database with several tables to further partition the data (blogs, pages, etc). My immediate reaction with Mongo would be to create a 'users' database with one collection per user. In this way user 'zach' blog entries would go into the 'zach' collection with associated comments and such becoming sub-objects in the same collection. Basically like dynamically creating one table per user in MySQL, but apparently without the complexity and limitations that might impose. Of course since I haven't really used Mongo before I'm having trouble gauging the (ahem..) quality of this idea and the potential problems it might cause down the road. I'd like user data to be treated a lot like a users directory in a *nix environment where user created/non-shared (mostly) gets put into one place (currently with MySQL that would be the appname_users as mentioned above). Most of the users data will be specific to the users page(s). Some of the user data which is queried across all site users (searchable user profiles) is currently kept in a separate database/table and I expect things like this could be put into a appname_system database and be broken up into collections and/or application specific databases (appname_profiles). Anyway, since the available documentation on this is currently a little thin and my experience is extremely limited I thought I might find a little guidance from someone with a better working understanding of the system. On the plus side I'd really already been attempting to treat MySQL as a schema-less document-store and doing this with Mongo seems much more intuitive/sane/rational so I'm really looking forward to getting started. Thanks, Zach

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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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  • An INSERT conditioned on COUNT

    - by Anders Feder
    How can I construct a MySQL INSERT query that only executes if the number of rows satisfying some condition already in the table is less than 20, and fails otherwise? That is, if the table has 18 rows satisfying the condition, then the INSERT should proceed. If the table has 23 rows satisfying the condition, then the INSERT should fail. For atomicity, I need to express this in a single query, so two requests can not INSERT at the same time, each in the 'belief' that only 19 rows satisfy the condition. Thank you.

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  • MySQLdb not INSERTING, _mysql does fine.

    - by Mad_Casual
    Okay, I log onto the MySQL command-line client as root. I then open or otherwise run a python app using the MySQLdb module as root. When I check the results using python (IDLE), everything looks fine. When I use the MySQL command-line client, no INSERT has occurred. If I change things around to _mysql instead of MySQLdb, everything works fine. I'd appreciate any clarification(s). "Works" until IDLE/Virtual machine is reset: <pre><code>import MySQLdb db = MySQLdb.connect(user='root', passwd='*******',db='test') cursor = db.cursor() cursor.execute("""INSERT INTO test VALUES ('somevalue');""",)</code></end> Works: <pre><code>import _mysql db = _mysql.connect(user='root', passwd='*******',db='test') db.query("INSERT INTO test VALUES ('somevalue');")</code></end> System info: Intel x86 WinXP Python 2.5 MySQL 5.1.41 MySQL-Python 1.2.2

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  • C# Exception when retrieving rows from a datagrid in virtual mode

    - by JamesM
    Hi all, I keep getting an exception (see below) when I retrieve a list of rows from a Virtual Mode datagrid, this only happens when I have more rows than I can display on screen and it doesn't happen every time. Is there anything I'm missing with regards to virtual mode? Update The image below shows the problem, the index is now outside the list range. The reason for this is say I have 10 items and I hide 5 as they are not needed and I want to run some code on the 5 that are visible, there are now 5 items but the index of some maybe between 5-9, how can I re-index? When I have run some code on the visible 5 I then show the hidden 5 so I don't want to disgard these, I'd need to reindex again when they are all visible. Many thanks.

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  • What database works well with 200+GB of data?

    - by taw
    I've been using mysql (with innodb; on Amazon rds) because it's sort of universal default, but it's been ridiculously under-performing, and tweaking it only delays the inevitable. The data is mostly relatively short (<1kB of bytes each) blobs information about 100Ms of urls. There is (or should be, mysql cannot seem to handle it) very high amount of insert / update / retrieve but few complex queries - not that complex queries wouldn't be useful, but because mysql is so slow that it's far faster to get the data out, process it locally, and cache the results somewhere. I can keep tweaking mysql and throwing more hardware at it, but it seems increasingly futile. So what are the options? SQL/relational model/etc. optional - anything will do as long as it's fast, networked, and language-independent.

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  • General JDBC Setup

    - by AeroDroid
    So I have a MySQL database set up on a Debian server and it works fine from a phpMyAdmin client. I'm currently working on a project to write a Java server that would be able to use the MySQL database that is already on this server through a JDBC connection. I've looked at many tutorials and documentations but all of them seem to just explain how to do client-side code, but I have yet to figure out how to even successfully open a JDBC connection to the server. As far as I am concerned, I believe that program has the drivers properly set up because it's not crashing anymore (I simply direct the Java Build Path of my program to the Connector/J provided by MySQL). As far as my program goes, this is what it looks like... import java.sql.*; public class JDBCTest { public static void main(String[] args) { System.out.println("Started!"); try { DriverManager.registerDriver(new com.mysql.jdbc.Driver()); System.out.println("Driver registered. Connecting..."); Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/", "root", "password"); System.out.println("Connected!"); conn.close(); } catch (SQLException e) { System.out.println("Error!"); e.printStackTrace(); } } } This is what's printed... Started! Driver registered. Connecting... It's as if the DriverManager.getConnection(String) just freezes there. I'm sure this is a problem with the server because when I intentionally misspell localhost, or an IP address, the program crashes within 20 seconds. This just hangs there forever. Sorry about this wall of text, but my final question is if anyone has any information what I should do or install on the server to get this to work? Thank you so much!

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  • Need help in Select query..

    - by Parth
    If I have four rows for a field with different values with other fields similar and then other four rows with same condition, as given below here u can see there different rows for insert with only difference in the "newvalue" and "field" excluding "id" for the table_name=jos_menu, operation=INSERT and live=0 now here what select query should be used to get only single row from the table on every change of table_name...??

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  • SQL Server 2000 DTS Package Failing with "The number of failing rows exceeds the maximum specified"

    - by Scott McCormick
    I have inherited a SQL Server 2000 DTS package that migrates data from SQL Server to Oracle. This package moves about 20 tables' data to Oracle every night with no transformations, and it is then transformed by a set of SPs and used by a GIS application. Twice this week, during the migration between SQL Server and Oracle, the package has failed with "The number of failing rows exceeds the maximum specified". It has failed on a different table each time, though. Each time it's failed, we've rerun the process the next morning and it has worked. Because the process works the second time it's run, it makes me think the data is being changed by someone or something between the initial failure and our successful second run. I would like to change the DTS package to log the failing rows in a text document so we can compare them later. Can someone help me with that? I can't seem to figure that part out. Scott

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  • How do you store accented characters coming from a web service into a database?

    - by Thierry Lam
    I have the following word that I fetch via a web service: André From Python, the value looks like: "Andr\u00c3\u00a9". The input is then decoded using json.loads: >>> import json >>> json.loads('{"name":"Andr\\u00c3\\u00a9"}') >>> {u'name': u'Andr\xc3\xa9'} When I store the above in a utf8 MySQL database, the data is stored like the following using Django: SomeObject.objects.create(name=u'Andr\xc3\xa9') Querying the name column from a mysql shell or displaying it in a web page gives: André The web page displays in utf8: <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> My database is configured in utf8: mysql> SHOW VARIABLES LIKE 'collation%'; +----------------------+-----------------+ | Variable_name | Value | +----------------------+-----------------+ | collation_connection | utf8_general_ci | | collation_database | utf8_unicode_ci | | collation_server | utf8_unicode_ci | +----------------------+-----------------+ 3 rows in set (0.00 sec) mysql> SHOW VARIABLES LIKE 'character_set%'; +--------------------------+----------------------------+ | Variable_name | Value | +--------------------------+----------------------------+ | character_set_client | utf8 | | character_set_connection | utf8 | | character_set_database | utf8 | | character_set_filesystem | binary | | character_set_results | utf8 | | character_set_server | utf8 | | character_set_system | utf8 | | character_sets_dir | /usr/share/mysql/charsets/ | +--------------------------+----------------------------+ 8 rows in set (0.00 sec) How can I retrieve the word André from a web service, store it properly in a database with no data loss and display it on a web page in its original form?

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  • Consolidating Columns in Excel

    - by New to iPhone
    I have two columns in excel like the following a,apple a,bannana a,orange a,plum b,apple b,berry b,orange b,grapefruit c,melon c,berry c,kiwi I need to consolidate them like this on a different sheet a,apple,bannana,orange,plum b,apple,berry,orange,grapefruit c,melon,berry,kiwi Any help would be appreciated

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  • Using SortableRows and know when rows have been moved

    - by DW
    I want to take advantage of the sortableRows property of the jqGrid. How do I detect when a row has been moved. I have studied the documentation and looked for examples but haven't found much. I do believe it is something like jQuery("#grid").sortableRows({connectWith:'#gird', ondrop: function(){ alert("row moved") }}); but that does not work. I can move the rows, but don't seemed to have trapped the event. Is there something wrong with my syntax or my approach in general. Basically, I need to know that the rows have been rearranged so I can be sure they get saved with their new order. Thanks

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  • Subrows into a row in GridView using WPF & C#

    - by toni
    hi! In my gridview I need to aggregate subrows into each row, something like in p2p emule/amule application where you can do double click to each file you are downloading and then under it you can see the parts of the file from where you are downloading. Is it possible in WPF? Thanks.

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  • Best way to stop SQL Injection in PHP

    - by Andrew G. Johnson
    So specifically in a mysql database. Take the following code and tell me what to do. // connect to the mysql database $unsafe_variable = $_POST["user-input"]; mysql_query("INSERT INTO table (column) VALUES ('" . $unsafe_variable . "')"); // disconnect from the mysql database

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  • Which are the RDBMS that minimize the server roundtrips? Which RDBMS are better (in this area) than

    - by user193655
    When the latency is high ("when pinging the server takes time") the server roundtrips make the difference. Now I don't want to focus on the roundtrips created in programming, but the roundtrips that occur "under the hood" in the DB engine, so the roundtrips that are 100% dependant on how the RDBMS is written itself. I have been told that FireBird has more roundtrips than MySQL. But this is the only information I know. I am currently supporting MS SQL but I'd like to change RDBMS (because I use Express Editions and in my scenario they are quite limiting from the performance point of view), so to make a wise choice I would like to include also this point into "my RDBMS comparison feature matrix" to understand which is the best RDBMS to choose as an alternative to MS SQL. So the bold sentence above would make me prefer MySQL to Firebird (for the roundtrips concept, not in general), but can anyone add informations? And MS SQL where is it located? Is someone able to "rank" the roundtrip performance of the main RDBMS, or at least: MS SQL, MySql, Postegresql, Firebird (I am not interested in Oracle since it is not free, and if I have to change I would change to a free RDBMS). Anyway MySql (as mentioned several times on stackoverflow) has a not clear future and a not 100% free license. So my final choice will probably dall on PostgreSQL or Firebird. Additional info: somehow you can answer my question by making a simple list like: MSSQL:3; MySQL:1; Firebird:2; Postgresql:2 (where 1 is good, 2 average, 3 bad). Of course if you can post some links where the roundtrips per RDBMSs are compared it would be great

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  • sql server swap data between rows problem

    - by AmRoSH
    I was asking b4 about swaping query to swap data between rows in same table and i got that qurey ALTER PROCEDURE [dbo].[VehicleReservationsSwap] -- Add the parameters for the stored procedure here (@FirstVehicleID int, @secondVehicleID int, @WhereClause nvarchar(2000)) AS BEGIN Create Table #Temp ( VehicleID int ,VehicleType nvarchar(100) ,JoinId int ) DECLARE @SQL varchar(8000) SET @SQL ='Insert into #Temp (VehicleID,VehicleType,JoinId) SELECT VehicleID,VehicleType,CASE WHEN VehicleID = ' + Cast(@FirstVehicleID as varchar(10)) + ' then ' + Cast(@secondVehicleID as varchar(10)) + ' ELSE ' + Cast(@FirstVehicleID as varchar(10)) + ' END AS JoinId FROM Reservations WHERE VehicleID in ( ' + Cast(@FirstVehicleID as varchar(10)) + ' , ' + Cast(@secondVehicleID as varchar(10)) + ' )' + @WhereClause EXEC(@SQL) --swap values UPDATE y SET y.VehicleID = #Temp.VehicleID ,y.VehicleType = #Temp.VehicleType FROM Reservations y INNER JOIN #Temp ON y.VehicleID = #Temp.JoinId WHERE y.VehicleID in (@FirstVehicleID,@secondVehicleID) Drop Table #Temp END this query take 2 parameters and swaping all rows returned for each parameter. the problem is the query swaps just if each parameter (forign key) has values I need to make swaping in case if one of them has no vlue. I hope if some one can help me in that . Thanks,

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  • JavaScript data grid for millions of rows

    - by Rudiger
    I need to present millions of rows of data to users in a grid using JavaScript. I don't want the user thinking about viewing finite pieces of data; it should appear that all of the data is available. Rather than downloading all the data at once, small chunks are downloaded as the user comes to them (by scrolling, keying in row numbers, searching). The rows will not be edited through this front end, so read-only answers are acceptable. What JavaScript data grids are best for this kind of seamless paging?

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  • Javascript timezone solution needed(taking into account the actual difference in UTC timestamps)

    - by user198729
    I have unix timestamps from time zone X which is not known, the current timestamp(now()) in TZ X is known 1275143019, how to approach a javascript function so that it can generate the datetime in the users current TZ in the format 2010-05-29 15:32:35 ? UPDATE I'm not a unix timestamp expert,if unix timestamp is always the same in different TZ, then I have to change the question a little,so that the current datetime in TZ X is known(like 2010-05-29 22:32:28),and the other datetime is also in this format,how to convert them to the user's TZ based on the difference between now() ? UPDATE Something strange from MySQL: On server: mysql> select now(); +---------------------+ | now() | +---------------------+ | 2010-05-29 18:34:30 | +---------------------+ 1 row in set (0.00 sec) mysql> select UNIX_TIMESTAMP(); +------------------+ | UNIX_TIMESTAMP() | +------------------+ | 1275143674 | +------------------+ 1 row in set (0.00 sec) On local: mysql> select now(); +---------------------+ | now() | +---------------------+ | 2010-05-29 22:41:30 | +---------------------+ 1 row in set (0.00 sec) mysql> select UNIX_TIMESTAMP(); +------------------+ | UNIX_TIMESTAMP() | +------------------+ | 1275144091 | +------------------+ 1 row in set (0.00 sec) Why the difference between now() (2010-05-29 22:41:30-2010-05-29 18:34:30=6hours) and UNIX_TIMESTAMP() (1275144091 - 1275143674 = 417seconds) is not the same ?

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  • JXTreeTable and BorderHighlighter Drawing Border on All Rows

    - by Kevin Rubin
    I'm using a BorderHighlighter on my JXTreeTable to put a border above each of the table cells on non-leaf rows to give a more clear visual separator for users. The problem is that when I expand the hierarchical column, all cells in the hierarchical column, for all rows, include the Border from the Highlighter. The other columns are displaying just fine. My BorderHighlighter is defined like this: Highlighter topHighlighter = new BorderHighlighter(new HighlightPredicate() { @Override public boolean isHighlighted(Component component, ComponentAdapter adapter) { TreePath path = treeTable.getPathForRow(adapter.row); TreeTableModel model = treeTable.getTreeTableModel(); Boolean isParent = !model.isLeaf(path.getLastPathComponent()); return isParent; } }, BorderFactory.createMatteBorder(2, 0, 0, 0, Color.RED)); I'm using SwingX 1.6.5.

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