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• SQL different joins not making any difference to result

  - by Chrissi

  I'm trying to write a quick (ha!) program to organise some of my financial information. What I ideally want is a query that will return all records with financial information in them from TableA. There should be one row for each month, but in instances where there were no transactions for a month there will be no record. I get results like this: SELECT Period,Year,TotalValue FROM TableA WHERE Year='1997' Result: Period Year TotalValue 1 1997 298.16 2 1997 435.25 4 1997 338.37 8 1997 336.07 9 1997 578.97 11 1997 361.23 By joining on a table (well a View in this instance) which just contains a field Period with values from 1 to 12, I expect to get something like this: SELECT p.Period,a.Year,a.TotalValue FROM Periods AS p LEFT JOIN TableA AS a ON p.Period = a.Period WHERE Year='1997' Result: Period Year TotalValue 1 1997 298.16 2 1997 435.25 3 NULL NULL 4 1997 338.37 5 NULL NULL 6 NULL NULL 7 NULL NULL 8 1997 336.07 9 1997 578.97 10 NULL NULL 11 1997 361.23 12 NULL NULL What I'm actually getting though is the same result no matter how I join it (except CROSS JOIN which goes nuts, but it's really not what I wanted anyway, it was just to see if different joins are even doing anything). LEFT JOIN, RIGHT JOIN, INNER JOIN all fail to provide the NULL records I am expecting. Is there something obvious that I'm doing wrong in the JOIN? Does it matter that I'm joining onto a View?

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• Parse large XML file w/ script or use BioPython API ?

  - by jeremy04

  Hey guys this is my first question on here. I'm trying to make a local copy of the UniprotKB in SQL. The UniprotKB is 2.1GB, and it comes in XML and a special text format used by SwissProt Here are my options: 1) Use a SAX parser (XML) - I chose Ruby, and Nokogiri. I started writing the parser, but my initial reaction: how would I map the XML schema to the SAX parser? 2) BioPython - I already have BioSQL/Biopython installed, which literally created my SQL schema for me, and I was able to successfully insert one SwissProt/Uniprot txt file into the database. I'm running it right now (crosses fingers) on the entire 2.1gb. Here is the code I'm running: from Bio import SeqIO from BioSQL import BioSeqDatabase from Bio import SwissProt server = BioSeqDatabase.open_database(driver = "MySQLdb", user = "root", passwd = "", host="localhost", db = "bioseqdb") db = server["uniprot"] iterator = SeqIO.parse(open("/path/to/uniprot_sprot.dat", "r"), "swiss") db.load(iterator) server.commit() Edit: it's now crashing because the transactions are getting locked (since the tables are Innodb) Error Number: 1205 Lock wait timeout exceeded; try restarting transaction. I'm using MySQL version: 5.1.43 Should I switch my database to Postgrelsql ?

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• Need some advice before starting coding my next iPhone app...

  - by Tom

  Hi! I need some advice about how should I start coding something. So here is the context: I've just finished building a CMS that manage a SQLite database. My application will be picking this database and use its content as the application's content. So far it's pretty simple. The application will have a navigation that will browse through various workflows, and once at the end workflow, it'll show contents from the database. A consultation kind a thing, example: Liquids - Juice - Orange Juice - Informations about Orange Juice. For my SQLite transactions, so far I believe I'll be using fmdb. It looks like a great wrapper. Here's a simple schema from one of the database: Workflow: id: { type: integer(3), primary: true, autoincrement: true } workflow_id: { type: integer(1) } name: { type: string(255) } That table's rows will be my navigations. Do you believe I should use a navigation controller? If so, then how could I generate the navigation tree from it? I have a good working knowledge of Objective-C and Foundation framework, but never went too far with it so that is why I'm asking before starting in the wrong direction :) Thanks a lot.

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• ecommerce platform or from scratch? customer specific catalogs and purchase orders

  - by rafi

  I have a possible freelance job in front of me for a distributor who wants product ordering set up but the orders are all P.O.s basically - no actual credit card or paypal transaction. The customer is simply billed and the order archived. Customers will need to login to this site and each customer will have their own custom catalog of a few dozen products which have been setup via a control panel this distributor uses. So there will be a master catalog of over 1,000 products (perhaps browsable but not to be ordered from on the site) but each customer will only be able to order from the products specified for their accounts. I know I can build this from scratch but I figured it's worth looking into what ecommerce platforms would get me a nice head start. Obviously shopping cart, order history, catalog management are concepts that I can reuse but are any of the ecommerce systems out there also capable of handling custom catalogs (maybe as multi-stores?) or transactions billed to accounts without credit card? The more I could reuse the better. I've messed with OSCommerce (way back) and a little Zen Cart more recently. I've also worked on a number of totally custom e-commerce sites. But my knowledge of the open source e-commerce tools is pretty limited and I'm trying to keep the effort as simple as I possibly can on this. I'm pretty flexible on the language of the platform by the way. Thanks in advance.

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• Uncommitted reads in SSIS

  - by OldBoy

  I'm trying to debug some legacy Integration Services code, and really want some confirmation on what I think the problem is: We have a very large data task inside a control flow container. This control flow container is set up with TransactionOption = supported - i.e. it will 'inherit' transactions from parent containers, but none are set up here. Inside the data flow there is a call to a stored proc that writes to a table with pseudo code something like: "If a record doesn't exist that matches these parameters then write it" Now, the issue is that there are three records being passed into this proc all with the same parameters, so logically the first record doesn't find a match and a record is created. The second record (with the same parameters) also doesn't find a match and another record is created. My understanding is that the first 'record' passed to the proc in the dataflow is uncommitted and therefore can't be 'read' by the second call. The upshot being that all three records create a row, when logically only the first should. In this scenario am I right in thinking that it is the uncommitted transaction that stops the second call from seeing the first? Even setting the isolation level on the container doesn't help because it's not being wrapped in a transaction anyway.... Hope that makes sense, and any advice gratefully received. Work-arounds confer god-like status on you.

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• Efficient database access when dealing with multiple abstracted repositories

  - by Nathan Ridley

  I want to know how most people are dealing with the repository pattern when it involves hitting the same database multiple times (sometimes transactionally) and trying to do so efficiently while maintaining database agnosticism and using multiple repositories together. Let's say we have repositories for three different entities; Widget, Thing and Whatsit. Each repository is abstracted via a base interface as per normal decoupling design processes. The base interfaces would then be IWidgetRepository, IThingRepository and IWhatsitRepository. Now we have our business layer or equivalent (whatever you want to call it). In this layer we have classes that access the various repositories. Often the methods in these classes need to do batch/combined operations where multiple repositories are involved. Sometimes one method may make use of another method internally, while that method can still be called independently. What about, in this scenario, when the operation needs to be transactional? Example: class Bob { private IWidgetRepository _widgetRepo; private IThingRepository _thingRepo; private IWhatsitRepository _whatsitRepo; public Bob(IWidgetRepository widgetRepo, IThingRepository thingRepo, IWhatsitRepository whatsitRepo) { _widgetRepo = widgetRepo; _thingRepo= thingRepo; _whatsitRepo= whatsitRepo; } public void DoStuff() { _widgetRepo.StoreSomeStuff(); _thingRepo.ReadSomeStuff(); _whatsitRepo.SaveSomething(); } public void DoOtherThing() { _widgetRepo.UpdateSomething(); DoStuff(); } } How do I keep my access to that database efficient and not have a constant stream of open-close-open-close on connections and inadvertent invocation of MSDTS and whatnot? If my database is something like SQLite, standard mechanisms like creating nested transactions are going to inherently fail, yet the business layer should not have to be concerning itself with such things. How do you handle such issues? Does ADO.Net provide simple mechanisms to handle this or do most people end up wrapping their own custom bits of code around ADO.Net to solve these types of problems?

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• object.valid? returns false but object.errors.full_messages is empty

  - by user549563

  Hello I'm confuse about objects that I can't save, simplified model is class Subscription < ActiveRecord::base belongs_to :user, :class_name => "User", :foreign_key => "user_id" has_many :transactions, :class_name => "SubscriptionTransaction" validates_presence_of :first_name, :message => "ne peut être vide" validates_presence_of :last_name, :message => "ne peut être vide" validates_presence_of :card_number, :message => "ne peut être vide" validates_presence_of :card_verification, :message => "ne peut être vide" validates_presence_of :card_type, :message => "ne peut être vide" validates_presence_of :card_expires_on, :message => "ne peut être vide" attr_accessor :card_number, :card_verification validate_on_create :validate_card def validate_card unless credit_card.valid? credit_card.errors.full_messages.each do |message| errors.add_to_base message end end end def credit_card @credit_card ||= ActiveMerchant::Billing::CreditCard.new( :type => card_type, :number => card_number, :verification_value => card_verification, :month => card_expires_on.month, :year => card_expires_on.year, :first_name => first_name, :last_name => last_name ) end end and in my subscription_controller if subscription.save # do something else debugger # means breakpoint where i try subscription.errors.full_messages # do something else end I tried to use ruby-debug for this adding a breakpoint before. And subscription.valid? return false which explains that ActiveRecord doesn't allow the save method. Unfortunately i can't know why the object is invalid. subscription.errors.full_messages # => [] I'm stucked, if you have any idea, thank you.

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• C# "Rename" Property in Derived Class

  - by Eric

  When you read this you'll be awfully tempted to give advice like "this is a bad idea for the following reason..." Bear with me. I know there are other ways to approach this. This question should be considered trivia. Lets say you have a class "Transaction" that has properties common to all transactions such as Invoice, Purchase Order, and Sales Receipt. Let's take the simple example of Transaction "Amount", which is the most important monetary amount for a given transaction. public class Transaction { public double Amount { get; set; } public TxnTypeEnum TransactionType { get; set; } } This Amount may have a more specific name in a derived type... at least in the real world. For example, the following values are all actually the same thing: Transaction - Amount Invoice - Subtotal PurchaseOrder - Total Sales Receipt - Amount So now I want a derived class "Invoice" that has a Subtotal rather than the generically-named Amount. Ideally both of the following would be true: In an instance of Transaction, the Amount property would be visible. In an instance of Invoice, the Amount property would be hidden, but the Subtotal property would refer to it internally. Invoice looks like this: public class Invoice : Transaction { new private double? Amount { get { return base.Amount; } set { base.Amount = value; } } // This property should hide the generic property "Amount" on Transaction public double? SubTotal { get { return Amount; } set { Amount = value; } } public double RemainingBalance { get; set; } } But of course Transaction.Amount is still visible on any instance of Invoice. Thanks for taking a look!

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• Entity and N-Tier architecture in C#

  - by acadia

  Hello, I have three tables as shown below Emp ---- empID int empName deptID empDetails ----------- empDetailsID int empID int empDocuments -------------- docID empID docName docType I am creating a entity class so that I can use n-tier architecture to do database transactions etc in C#. I started creating class for the same as shown below using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace employee { class emp { private int empID; private string empName; private int deptID; public int EmpID { get; set; } public string EmpName { get; set; } public int deptID { get; set; } } } My question is as empDetails and empDocuments are related to emp by empID. How do I have those in my emp class. I would appreciate if you can direct me to an example. Thanks

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• I have data about deadlocks, but I can't understand why they occur

  - by Alex

  I am receiving a lot of deadlocks in my big web application. http://stackoverflow.com/questions/2941233/how-to-automatically-re-run-deadlocked-transaction-asp-net-mvc-sql-server Here I wanted to re-run deadlocked transactions, but I was told to get rid of the deadlocks - it's much better, than trying to catch the deadlocks. So I spent the whole day with SQL Profiler, setting the tracing keys etc. And this is what I got. There's a Users table. I have a very high usable page with the following query (it's not the only query, but it's the one that causes troubles) UPDATE Users SET views = views + 1 WHERE ID IN (SELECT AuthorID FROM Articles WHERE ArticleID = @ArticleID) And then there's the following query in ALL pages: User = DB.Users.SingleOrDefault(u => u.Password == password && u.Name == username); That's where I get User from cookies. Very often a deadlock occurs and this second Linq-to-SQL query is chosen as a victim, so it's not run, and users of my site see an error screen. I read a lot about deadlocks... And I don't understand why this is causing a deadlock. So obviously both of this queries run very often. At least once a second. Maybe even more often (300-400 users online). So they can be run at the same time very easily, but why does it cause a deadlock? Please help. Thank you

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• C# threading solution for long queries

  - by Eddie

  Senerio We have an application that records incidents. An external database needs to be queried when an incident is approved by a supervisor. The queries to this external database are sometimes taking a while to run. This lag is experienced through the browser. Possible Solution I want to use threading to eliminate the simulated hang to the browser. I have used the Thread class before and heard about ThreadPool. But, I just found BackgroundWorker in this post. MSDN states: The BackgroundWorker class allows you to run an operation on a separate, dedicated thread. Time-consuming operations like downloads and database transactions can cause your user interface (UI) to seem as though it has stopped responding while they are running. When you want a responsive UI and you are faced with long delays associated with such operations, the BackgroundWorker class provides a convenient solution. Is BackgroundWorker the way to go when handling long running queries? What happens when 2 or more BackgroundWorker processes are ran simultaneously? Is it handled like a pool?

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• How to use Transaction in Entity FrameWork?

  - by programmerist

  How to use Transaction in Entity FrameWork? i read some links on Stackoverflow : http://stackoverflow.com/questions/815586/entity-framework-using-transactions-or-savechangesfalse-and-acceptallchanges BUT; i have 3 table so i have 3 entities: CREATE TABLE Personel (PersonelID integer PRIMARY KEY identity not null, Ad varchar(30), Soyad varchar(30), Meslek varchar(100), DogumTarihi datetime, DogumYeri nvarchar(100), PirimToplami float); Go create TABLE Prim (PrimID integer PRIMARY KEY identity not null, PersonelID integer Foreign KEY references Personel(PersonelID), SatisTutari int, Prim float, SatisTarihi Datetime); Go CREATE TABLE Finans (ID integer PRIMARY KEY identity not null, Tutar float); Personel, Prim,Finans my tables. if you look Prim table you can see Prim value float value if i write a textbox not float value my transaction must run. using (TestEntities testCtx = new TestEntities()) { using (TransactionScope scope = new TransactionScope()) { // do someyihng... testCtx.Personel.SaveChanges(); // do someyihng... testCtx.Prim.SaveChanges(); // do someyihng... testCtx.Finans.SaveChanges(); scope .Complete(); success = true; } } How can i do that?

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• google app engine atomic section???

  - by bokertov

  hi, Say you retrieve a set of records from the datastore (something like: select * from MyClass where reserved='false'). how do i ensure that another user doesn't set the reserved is still false? I've looked in the Transaction documentation and got shocked from google's solution which is to catch the exception and retry in a loop. Any solution that I'm missing - it's hard to believe that there's no way to have an atomic operation in this environment. (btw - i could use 'syncronize' inside the servlet but i think it's not valid as there's no way to ensure that there's only one instance of the servlet object, isn't it? same applies to static variable solution) Any idea on how to solve??? (here's the google solution: http://code.google.com/appengine/docs/java/datastore/transactions.html#Entity_Groups look at: Key k = KeyFactory.createKey("Employee", "k12345"); Employee e = pm.getObjectById(Employee.class, k); e.counter += 1; pm.makePersistent(e); This requires a transaction because the value may be updated by another user after this code fetches the object, but before it saves the modified object. Without a transaction, the user's request will use the value of counter prior to the other user's update, and the save will overwrite the new value. With a transaction, the application is told about the other user's update. If the entity is updated during the transaction, then the transaction fails with an exception. The application can repeat the transaction to use the new data. THANKS!

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• MySQL Config File for Large System

  - by Jonathon

  We are running MySQL on a Windows 2003 Server Enterpise Edition box. MySQL is about the only program running on the box. We have approx. 8 slaves replicated to it, but my understanding is that having multiple slaves connecting to the same master does not significantly slow down performance, if at all. The master server has 16G RAM, 10 Terabyte drives in RAID 10, and four dual-core processors. From what I have seen from other sites, we have a really robust machine as our master db server. We just upgraded from a machine with only 4G RAM, but with similar hard drives, RAID, etc. It also ran Apache on it, so it was our db server and our application server. It was getting a little slow, so we split the db server onto this new machine and kept the application server on the first machine. We also distributed the application load amongst a few of our other slave servers, which also run the application. The problem is the new db server has mysqld.exe consuming 95-100% of CPU almost all the time and is really causing the app to run slowly. I know we have several queries and table structures that could be better optimized, but since they worked okay on the older, smaller server, I assume that our my.ini (MySQL config) file is not properly configured. Most of what I see on the net is for setting config files on small machines, so can anyone help me get the my.ini file correct for a large dedicated machine like ours? I just don't see how mysqld could get so bogged down! FYI: We have about 100 queries per second. We only use MyISAM tables, so skip-innodb is set in the ini file. And yes, I know it is reading the ini file correctly because I can change some settings (like the server-id and it will kill the server at startup). Here is the my.ini file: #MySQL Server Instance Configuration File # ---------------------------------------------------------------------- # Generated by the MySQL Server Instance Configuration Wizard # # # Installation Instructions # ---------------------------------------------------------------------- # # On Linux you can copy this file to /etc/my.cnf to set global options, # mysql-data-dir/my.cnf to set server-specific options # (@localstatedir@ for this installation) or to # ~/.my.cnf to set user-specific options. # # On Windows you should keep this file in the installation directory # of your server (e.g. C:\Program Files\MySQL\MySQL Server X.Y). To # make sure the server reads the config file use the startup option # "--defaults-file". # # To run run the server from the command line, execute this in a # command line shell, e.g. # mysqld --defaults-file="C:\Program Files\MySQL\MySQL Server X.Y\my.ini" # # To install the server as a Windows service manually, execute this in a # command line shell, e.g. # mysqld --install MySQLXY --defaults-file="C:\Program Files\MySQL\MySQL Server X.Y\my.ini" # # And then execute this in a command line shell to start the server, e.g. # net start MySQLXY # # # Guildlines for editing this file # ---------------------------------------------------------------------- # # In this file, you can use all long options that the program supports. # If you want to know the options a program supports, start the program # with the "--help" option. # # More detailed information about the individual options can also be # found in the manual. # # # CLIENT SECTION # ---------------------------------------------------------------------- # # The following options will be read by MySQL client applications. # Note that only client applications shipped by MySQL are guaranteed # to read this section. If you want your own MySQL client program to # honor these values, you need to specify it as an option during the # MySQL client library initialization. # [client] port=3306 [mysql] default-character-set=latin1 # SERVER SECTION # ---------------------------------------------------------------------- # # The following options will be read by the MySQL Server. Make sure that # you have installed the server correctly (see above) so it reads this # file. # [mysqld] # The TCP/IP Port the MySQL Server will listen on port=3306 #Path to installation directory. All paths are usually resolved relative to this. basedir="D:/MySQL/" #Path to the database root datadir="D:/MySQL/data" # The default character set that will be used when a new schema or table is # created and no character set is defined default-character-set=latin1 # The default storage engine that will be used when create new tables when default-storage-engine=MYISAM # Set the SQL mode to strict #sql-mode="STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION" # we changed this because there are a couple of queries that can get blocked otherwise sql-mode="" #performance configs skip-locking max_allowed_packet = 1M table_open_cache = 512 # The maximum amount of concurrent sessions the MySQL server will # allow. One of these connections will be reserved for a user with # SUPER privileges to allow the administrator to login even if the # connection limit has been reached. max_connections=1510 # Query cache is used to cache SELECT results and later return them # without actual executing the same query once again. Having the query # cache enabled may result in significant speed improvements, if your # have a lot of identical queries and rarely changing tables. See the # "Qcache_lowmem_prunes" status variable to check if the current value # is high enough for your load. # Note: In case your tables change very often or if your queries are # textually different every time, the query cache may result in a # slowdown instead of a performance improvement. query_cache_size=168M # The number of open tables for all threads. Increasing this value # increases the number of file descriptors that mysqld requires. # Therefore you have to make sure to set the amount of open files # allowed to at least 4096 in the variable "open-files-limit" in # section [mysqld_safe] table_cache=3020 # Maximum size for internal (in-memory) temporary tables. If a table # grows larger than this value, it is automatically converted to disk # based table This limitation is for a single table. There can be many # of them. tmp_table_size=30M # How many threads we should keep in a cache for reuse. When a client # disconnects, the client's threads are put in the cache if there aren't # more than thread_cache_size threads from before. This greatly reduces # the amount of thread creations needed if you have a lot of new # connections. (Normally this doesn't give a notable performance # improvement if you have a good thread implementation.) thread_cache_size=64 #*** MyISAM Specific options # The maximum size of the temporary file MySQL is allowed to use while # recreating the index (during REPAIR, ALTER TABLE or LOAD DATA INFILE. # If the file-size would be bigger than this, the index will be created # through the key cache (which is slower). myisam_max_sort_file_size=100G # If the temporary file used for fast index creation would be bigger # than using the key cache by the amount specified here, then prefer the # key cache method. This is mainly used to force long character keys in # large tables to use the slower key cache method to create the index. myisam_sort_buffer_size=64M # Size of the Key Buffer, used to cache index blocks for MyISAM tables. # Do not set it larger than 30% of your available memory, as some memory # is also required by the OS to cache rows. Even if you're not using # MyISAM tables, you should still set it to 8-64M as it will also be # used for internal temporary disk tables. key_buffer_size=3072M # Size of the buffer used for doing full table scans of MyISAM tables. # Allocated per thread, if a full scan is needed. read_buffer_size=2M read_rnd_buffer_size=8M # This buffer is allocated when MySQL needs to rebuild the index in # REPAIR, OPTIMZE, ALTER table statements as well as in LOAD DATA INFILE # into an empty table. It is allocated per thread so be careful with # large settings. sort_buffer_size=2M #*** INNODB Specific options *** innodb_data_home_dir="D:/MySQL InnoDB Datafiles/" # Use this option if you have a MySQL server with InnoDB support enabled # but you do not plan to use it. This will save memory and disk space # and speed up some things. skip-innodb # Additional memory pool that is used by InnoDB to store metadata # information. If InnoDB requires more memory for this purpose it will # start to allocate it from the OS. As this is fast enough on most # recent operating systems, you normally do not need to change this # value. SHOW INNODB STATUS will display the current amount used. innodb_additional_mem_pool_size=11M # If set to 1, InnoDB will flush (fsync) the transaction logs to the # disk at each commit, which offers full ACID behavior. If you are # willing to compromise this safety, and you are running small # transactions, you may set this to 0 or 2 to reduce disk I/O to the # logs. Value 0 means that the log is only written to the log file and # the log file flushed to disk approximately once per second. Value 2 # means the log is written to the log file at each commit, but the log # file is only flushed to disk approximately once per second. innodb_flush_log_at_trx_commit=1 # The size of the buffer InnoDB uses for buffering log data. As soon as # it is full, InnoDB will have to flush it to disk. As it is flushed # once per second anyway, it does not make sense to have it very large # (even with long transactions). innodb_log_buffer_size=6M # InnoDB, unlike MyISAM, uses a buffer pool to cache both indexes and # row data. The bigger you set this the less disk I/O is needed to # access data in tables. On a dedicated database server you may set this # parameter up to 80% of the machine physical memory size. Do not set it # too large, though, because competition of the physical memory may # cause paging in the operating system. Note that on 32bit systems you # might be limited to 2-3.5G of user level memory per process, so do not # set it too high. innodb_buffer_pool_size=500M # Size of each log file in a log group. You should set the combined size # of log files to about 25%-100% of your buffer pool size to avoid # unneeded buffer pool flush activity on log file overwrite. However, # note that a larger logfile size will increase the time needed for the # recovery process. innodb_log_file_size=100M # Number of threads allowed inside the InnoDB kernel. The optimal value # depends highly on the application, hardware as well as the OS # scheduler properties. A too high value may lead to thread thrashing. innodb_thread_concurrency=10 #replication settings (this is the master) log-bin=log server-id = 1 Thanks for all the help. It is greatly appreciated.

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• Mono Text Based Web Browser

  - by powerbox

  Hi guys, is there any public text based web browser implementation for C# or on mono base api that I can use to fill up web forms automatically? I'll be using it to automate some web task that does not require any image authentication. I'm currently using a web browser control available on .Net Framework and waits for the event WebBrowserDocumentCompletedEventHandler to fire after a page is successfully loaded and invoke some actions like Submit or simulating a mouse click on some links. It actually does the job but I can't process bulk transactions since I needed to wait for the whole page to be loaded together with the images and other stuff. It is easy to use HttpWebRequest to fill up some forms , provide some data and then submit. But on some occasions I only need to simulate a mouse click to a certain link which I don't know how to do with HttpWebRequest. By the way using HttpWebRequest will still download all the images of a web page that I see pointless since I only need to provide correct data back to the server. I hope someone can pinpoint me the correct way of doing this kind of automation and thanks in advance!

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• Are reads and (transactional) writes faster for entities of the same group than otherwise?

  - by indiehacker

  What advantage is there to designing child-parent relationships, which allow us to do writes in transactions, when there is never a real concern for consistency and contention and those sort of more complex issues? Does it make writes and reads faster? Consider my situation where there are many .png images that are referenced to one mosaic layer, and these .png images are written just once by a single user. The user can design many mosaic layers and her mosaic layers and referenced image entities are never changed/updated, they are just deleted some time in the future. Other users can come to the web project site and interactively view the mosaic layer as different layouts/configurations of the images as they play (query) with different criteria. So reads should be very fast. So there is no real worry of contention, or users conflicting with one another with writing new image entities. And because of that I am assuming there is no "requirement" for the .png image entities to be grouped by their same mosaic layer in child-parent relationship. However, perhaps, since the documentation says they are stored close to one another, if the many image entities were grouped as children to a single mosaic layer parent than this has the advantage that the writing (in transaction) and reading will happen much faster?

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• including pre-built java classes into an android project

  - by moonlightcheese

  i'm trying to include a maven java project into my android project. the maven project is the greader-unofficial project which allows developers access to google reader accounts, and handles all of the http transactions and URI/URL building, making grabbing feeds and items from google reader transparent to the developer. the project is available here: http://code.google.com/p/greader-unofficial/ the code is originally written for the standard jdk and uses classes from java.net that are not a part of the standard Android SDK. i actually tried to manually resolve all dependencies and ran into a problem when i got as far as including com.sun.syndication pieces required by the class be.lechtitseb.google.reader.api.util.AtomUtil.java... some of the classes in java.net that are in the standard jdk (i'm using 1.6) are not in the Android SDK. in addition, resolving all of these dependencies manually is just ridiculous when i'm compiling a maven project that should be pretty simple. however, i can use maven to compile the sources with no issue. how can i include this maven project, which is dependent on the complete jdk, into my android project in such a way that it will compile so that i can access the GoogleReader class from my android project? and for the record, i don't have the expertise to rewrite this entire api to work with the standard Android SDK.

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• How to properly cast a global memory array using the uint4 vector in CUDA to increase memory throughput?

  - by charis

  There are generally two techniques to increase the memory throughput of the global memory on a CUDA kernel; memory accesses coalescence and accessing words of at least 4 bytes. With the first technique accesses to the same memory segment by threads of the same half-warp are coalesced to fewer transactions while be accessing words of at least 4 bytes this memory segment is effectively increased from 32 bytes to 128. To access 16-byte instead of 1-byte words when there are unsigned chars stored in the global memory, the uint4 vector is commonly used by casting the memory array to uint4: uint4 *text4 = ( uint4 * ) d_text; var = text4[i]; In order to extract the 16 chars from var, i am currently using bitwise operations. For example: s_array[j * 16 + 0] = var.x & 0x000000FF; s_array[j * 16 + 1] = (var.x >> 8) & 0x000000FF; s_array[j * 16 + 2] = (var.x >> 16) & 0x000000FF; s_array[j * 16 + 3] = (var.x >> 24) & 0x000000FF; My question is, is it possible to recast var (or for that matter *text4) to unsigned char in order to avoid the additional overhead of the bitwise operations?

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• Database solution for 200million writes/day, monthly summarization queries

  - by sb

  Hello. I'm looking for help deciding on which database system to use. (I've been googling and reading for the past few hours; it now seems worthwhile to ask for help from someone with firsthand knowledge.) I need to log around 200 million rows (or more) per 8 hour workday to a database, then perform weekly/monthly/yearly summary queries on that data. The summary queries would be for collecting data for things like billing statements, eg. "How many transactions of type A did each user run this month?" (could be more complex, but that's the general idea). I can spread the database amongst several machines, as necessary, but I don't think I can take old data offline. I'll definitely need to be able to query a month's worth of data, maybe a year. These queries would be for my own use, and wouldn't need to be generated in real-time for an end-user (they could run overnight, if needed). Does anyone have any suggestions as to which databases would be a good fit? P.S. Cassandra looks like it would have no problem handling the writes, but what about the huge monthly table scans? Is anyone familiar with Cassandra/Hadoop MapReduce performance?

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• How to efficiently use LOCK_ESCALATION mssql 2008

  - by Avias

  I'm currently having troubles with frequent deadlocks with a specific user table in MS SQL 2008. Here are some facts about this particular table: Has a large amount of rows (1 to 2 million) All the indexes used on this table only has "use row lock" ticked on its option rows are frequently updated by multiple transactions but are unique (e.g. probably a thousand or more update statements are executed to different unique rows every hour) the table does not use partitions. Upon checking the table on sys.tables, I found that the lock_escalation is set to TABLE I'm very tempted to turn the lock_escalation for this table to DISABLE but I'm not really sure what side effect this would incur. From What I understand, using DISABLE will minimize escalating locks to TABLE level which if combined with the row lock settings of the indexes should theoretically minimize the deadlocks I am encountering.. From what I have read in Determining threshold for lock escalation it seems that locking automatically escalates when a single transaction fetches 5000 rows.. What does a single transaction mean in this sense? A single session/connection getting 5000 rows thru individual update/select statements? Or is it a single sql update/select statement that fetches 5000 or more rows? Any insight is appreciated, btw, n00b DBA here Thanks

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• Common Properties: Consolidating Loan, Purchase, Inventory and Sale tables into one Transaction tabl

  - by Frank Computer

  Pawnshop Application: I have separate tables for Loan, Purchase, Inventory & Sales transactions. Each tables rows are joined to their respective customer rows by: customer.pk [serial] = loan.fk [integer]; = purchase.fk [integer]; = inventory.fk [integer]; = sale.fk [integer]; Since there are so many common properties within the four tables, I consolidated the four tables into one table called "transaction", where a column: transaction.trx_type char(1) {L=Loan, P=Purchase, I=Inventory, S=Sale} Scenario: A customer initially pawns merchandise, makes a couple of interest payments, then decides he wants to sell the merchandise to the pawnshop, who then places merchandise in Inventory and eventually sells it to another customer. I designed a generic transaction table where for example: transaction.main_amount DECIMAL(7,2) in a loan transaction holds the pawn amount, in a purchase holds the purchase price, in inventory and sale holds sale price. This is clearly a denormalized design, but has made programming alot easier and improved performance. Any type of transaction can now be performed from within one screen, without the need to change to different tables.

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• I have data about deadlocks, but I can't understand why they occur (MS SQL/ASP.NET MVC)

  - by Alex

  I am receiving a lot of deadlocks in my big web application. http://stackoverflow.com/questions/2941233/how-to-automatically-re-run-deadlocked-transaction-asp-net-mvc-sql-server Here I wanted to re-run deadlocked transactions, but I was told to get rid of the deadlocks - it's much better, than trying to catch the deadlocks. So I spent the whole day with SQL profiler, setting the tracing keys etc. And this is what I got. There's a Users table. I have a very high usable page with the following query (it's not the only query, but it's the one that causes troubles) UPDATE Users SET views = views + 1 WHERE ID IN (SELECT AuthorID FROM Articles WHERE ArticleID = @ArticleID) And then there's the following query in ALL pages: User = DB.Users.SingleOrDefault(u => u.Password == password && u.Name == username); That's where I get User from cookies. Very often a deadlock occurs and this second LINQ TO SQL query is chosen as a victim, so it's not run, and users of my site see an error screen. I read a lot about deadlocks... And I don't understand why this is causing a deadlock. So obviously both of this queries run very often. At least once a second. Maybe even more often (300-400 users online). So they can be run at the same time very easily, but why does it cause a deadlock? Please help. Thank you

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• Using ddply() to Get Frequency of Certain IDs, by Appearance in Multiple Rows (in R)

  - by EconomiCurtis

  Goal If the following description is hard follow, please see the example "before" and "after" to see a straightforward example. I have bartering data, with unique trade ids, and two sides of the trade. Side1 and Side2 are baskets, lists of item ids that represent both sides of the barter transaction. I'd like to count the frequency each ITEM appears in TRADES. E.g, if item "001" appeared in 3 trades, I'd have a count of 3 (ignoring how many times the item appeared in each trade). Further, I'd like to do this with the plyr ddply function. (If you're interested as to my motivation, I working over many hundreds of thousands of transactions and am already using a ddply to calculate several other summary statistics. I'd like to add this to the ddply I'm already using, rather than calculate it after, and merge it into the ddply output.... sorry if that was difficult to follow.) In terms of pseudo code I'm working off of: merge each row of Side1 and Side2 by row, get unique() appearances of each item id apply table() function transpose and relabel output from table Example of the structure of my data, and the output I desire. Data Example (before): df <- data.frame(TradeID = c("01","02","03","04")) df$Side1 = list(c("001","001","002"), c("002","002","003"), c("001","004"), c("001","002","003","004")) df$Side2 = list(c("001"),c("007"),c("009"),c()) Desired Output (after): df.ItemRelFreq_byTradeID <- data.frame(ItemID = c("001","002","003","004","007","009"), RelFreq_byTrade = c(3,3,2,2,1,1)) One method to do this without ddply I've worked out one way to do this below. My problem is that I can't quite seem to get ddply to do this for me. temp <- table(unlist(sapply(mapply(c,df$Side1,df$Side2), unique))) df.ItemRelFreq_byTradeID <- data.frame(ItemID = names(temp), RelFreq_byTrade = temp[]) Thanks for any help you can offer! Curtis

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• Infrastructure for high transactional system (language & hosting suggestion help)

  - by RPS

  Some of our friends (University students) are trying to develop a twitter type application, I want to plan for at least 1000 transactions per second (I know it's wishful thinking) for initial launch. This involves several people connecting and getting updates and posting (text + images) to site. In the back end db will server the data and also calculates rankings of what to push to user based on complex algorithm on the fly real-time. Our group is familiar with Java and Tomcat/MySQL. We can also easily learn/code in PHP/MySQL. What is the best suited platform for our purpose ? Though Java seem to be easy to implement for us I am afraid that hosting will be a bit difficult. I could find cloud based php hosting services (like rackspace cloudsites) at reasonable cost. Amazon EC2 is a bit over our heads to manage on day-to-day. Also any recommendation on hosting ? (PHP or Java) We don't have millions in seed money but about $20K to start with. Any advice on above or any thing in general approach is much appreciated.

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• HAProxy causing delay

  - by user1221444

  I am trying to configure HAProxy to do load balancing for a custom webserver I created. Right now I am noticing an increasing delay with HAProxy as the size of the return message increases. For example, I ran four different tests, here are the results: Response 15kb through HAProxy: Avg. response time: .34 secs Transacation rate: 763 trans/sec Throughput: 11.08 MB/sec Response 2kb through HAProxy: Avg. response time: .08 secs Transaction rate: 1171 trans / sec Throughput: 2.51 MB/sec Response 15kb directly to server: Avg. response time: .11 sec Transaction rate: 1046 trans/sec throughput: 15.20 MB/sec Response 2kb directly to server: Avg. Response time: .05 secs Transaction rate: 1158 trans/sec Throughput: 2.48 MB/sec All transactions are HTTP requests. As you can see, there seems to be a much bigger difference between response times for when the response is bigger, than when it is smaller. I understand there will be a slight delay when using HAProxy. Not sure if it matters, but the test itself was run using siege. And during the test there was only one server behind the HAProxy(the same that was used in the direct to server tests). Here is my haproxy.config file: global log 127.0.0.1 local0 log 127.0.0.1 local1 notice maxconn 10000 user haproxy group haproxy daemon #debug defaults log global mode http option httplog option dontlognull retries 3 option redispatch option httpclose maxconn 10000 contimeout 10000 clitimeout 50000 srvtimeout 50000 balance roundrobin stats enable stats uri /stats listen lb1 10.1.10.26:80 maxconn 10000 server app1 10.1.10.200:8080 maxconn 5000 I couldn't find much in terms of options in this file that would help my problem. I have heard suggestions that I may have to adjust a few of my sysctl settings. I could not find a lot of information on this however, most documentation is for Linux 2.4 and 2.6 on the sysctl stuff, I am running 3.2(Ubuntu server 12.04), which seems to auto tuning, so I have no clue what I should or shouldn't be changing. Most settings changes I tried had no effect or a negative effect on performance. Just a notice, this is a very preliminary test, and my hope is that at deployment time, my HAProxy will be able to balance 10k-20k requests/sec to many servers, so if anyone could provide information to help me reach that goal, it would be much appreciated. Thank you very much for any information you can provide. And if you need anymore information from me please let me know, I will get you anything I can.

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