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  • Optimizing MySQL for ALTER TABLE of InnoDB

    - by schuilr
    Sometime soon we will need to make schema changes to our production database. We need to minimize downtime for this effort, however, the ALTER TABLE statements are going to run for quite a while. Our largest tables have 150 million records, largest table file is 50G. All tables are InnoDB, and it was set up as one big data file (instead of a file-per-table). We're running MySQL 5.0.46 on an 8 core machine, 16G memory and a RAID10 config. I have some experience with MySQL tuning, but this usually focusses on reads or writes from multiple clients. There is lots of info to be found on the Internet on this subject, however, there seems to be very little information available on best practices for (temporarily) tuning your MySQL server to speed up ALTER TABLE on InnoDB tables, or for INSERT INTO .. SELECT FROM (we will probably use this instead of ALTER TABLE to have some more opportunities to speed things up a bit). The schema changes we are planning to do is adding a integer column to all tables and make it the primary key, instead of the current primary key. We need to keep the 'old' column as well so overwriting the existing values is not an option. What would be the ideal settings to get this task done as quick as possible?

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  • SQL Server Multiple Joins Are Taxing The CPU

    - by durilai
    I have a stored procedure on SQL Server 2005. It is pulling from a Table function, and has two joins. When the query is run using a load test it kills the CPU 100% across all 16 cores! I have determined that removing one of the joins makes the query run fine, but both taxes the CPU. Select SKey From dbo.tfnGetLatest(@ID) a left join [STAGING].dbo.RefSrvc b on a.LID = b.ESIID left join [STAGING].dbo.RefSrvc c on a.EID = c.ESIID Any help is appreciated, note the join is happening on the same table in a different database on the same server.

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  • How can "set timestamp" be a slow query?

    - by Peder
    My slow query log is full of entries like the following # Query_time: 1.016361 Lock_time: 0.000000 Rows_sent: 0 Rows_examined: 0 SET timestamp=1273826821; COMMIT; I guess the set timestamp command is issued by replication but I don't understand how set timestamp can take over a second. Any ideas?

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  • Flash causing jerky javascript animations

    - by Matt Brailsford
    Hi Guys, I'm developing a site which has a flash background playing a small video loop scaled to fill the whole background. Over the top I have a number of HTML elements which are animated using javascript. The problem I am having is that (predominantly in FF, but also in others to a lesser degree) the flash seems to be causing my javascript animations to run rather jerky, and in some cases missing the animation altogether and just jumping to the end state. Does anybody have any thoughts on how to make the 2 work together nicely? Many thanks Matt

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  • Getting "on the wire" Size of Messages in WCF

    - by Mystagogue
    While I'm making SOAP or REST invocations to WCF, I'd like to have the channel stack on either end (client and server) record the on-the-wire size of the data received. So I'm guessing I need to add a custom behavior to the channel stack on either side. That is, on the server side I'd record the IP-header advertised size that was received. On the client side I'd record the IP-header advertised size that was returned from the server. But this presupposes that this information is visible to a custom WCF behavior at the channel stack level. Perhaps it is only visible at the level of ASP.NET (at a layer beneath WCF)? In short, does anyone have any further insight on if and how this information is accessible? I must qualify that this "size" data will be collected in a production environment, as part of regular business logic calls. This question is related to my earlier bandwidth question.

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  • PL/SQL profiler missing data

    - by user289429
    We are using pl/sql profiler to collect metrics. We noticed that on one of the environment the plsql_profiler_runs table is populated with the total execution time but the finer details that gets collected in the table plsql_profiler_data is missing. Any idea why this would be happening? We do use dbms_profiler.flush_data() before stopping the profiler and have seen this work fine in another environment.

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  • Why is insertion into my tree faster on sorted input than random input?

    - by Juliet
    Now I've always heard binary search trees are faster to build from randomly selected data than ordered data, simply because ordered data requires explicit rebalancing to keep the tree height at a minimum. Recently I implemented an immutable treap, a special kind of binary search tree which uses randomization to keep itself relatively balanced. In contrast to what I expected, I found I can consistently build a treap about 2x faster and generally better balanced from ordered data than unordered data -- and I have no idea why. Here's my treap implementation: http://pastebin.com/VAfSJRwZ And here's a test program: using System; using System.Collections.Generic; using System.Linq; using System.Diagnostics; namespace ConsoleApplication1 { class Program { static Random rnd = new Random(); const int ITERATION_COUNT = 20; static void Main(string[] args) { List<double> rndTimes = new List<double>(); List<double> orderedTimes = new List<double>(); rndTimes.Add(TimeIt(50, RandomInsert)); rndTimes.Add(TimeIt(100, RandomInsert)); rndTimes.Add(TimeIt(200, RandomInsert)); rndTimes.Add(TimeIt(400, RandomInsert)); rndTimes.Add(TimeIt(800, RandomInsert)); rndTimes.Add(TimeIt(1000, RandomInsert)); rndTimes.Add(TimeIt(2000, RandomInsert)); rndTimes.Add(TimeIt(4000, RandomInsert)); rndTimes.Add(TimeIt(8000, RandomInsert)); rndTimes.Add(TimeIt(16000, RandomInsert)); rndTimes.Add(TimeIt(32000, RandomInsert)); rndTimes.Add(TimeIt(64000, RandomInsert)); rndTimes.Add(TimeIt(128000, RandomInsert)); string rndTimesAsString = string.Join("\n", rndTimes.Select(x => x.ToString()).ToArray()); orderedTimes.Add(TimeIt(50, OrderedInsert)); orderedTimes.Add(TimeIt(100, OrderedInsert)); orderedTimes.Add(TimeIt(200, OrderedInsert)); orderedTimes.Add(TimeIt(400, OrderedInsert)); orderedTimes.Add(TimeIt(800, OrderedInsert)); orderedTimes.Add(TimeIt(1000, OrderedInsert)); orderedTimes.Add(TimeIt(2000, OrderedInsert)); orderedTimes.Add(TimeIt(4000, OrderedInsert)); orderedTimes.Add(TimeIt(8000, OrderedInsert)); orderedTimes.Add(TimeIt(16000, OrderedInsert)); orderedTimes.Add(TimeIt(32000, OrderedInsert)); orderedTimes.Add(TimeIt(64000, OrderedInsert)); orderedTimes.Add(TimeIt(128000, OrderedInsert)); string orderedTimesAsString = string.Join("\n", orderedTimes.Select(x => x.ToString()).ToArray()); Console.WriteLine("Done"); } static double TimeIt(int insertCount, Action<int> f) { Console.WriteLine("TimeIt({0}, {1})", insertCount, f.Method.Name); List<double> times = new List<double>(); for (int i = 0; i < ITERATION_COUNT; i++) { Stopwatch sw = Stopwatch.StartNew(); f(insertCount); sw.Stop(); times.Add(sw.Elapsed.TotalMilliseconds); } return times.Average(); } static void RandomInsert(int insertCount) { Treap<double> tree = new Treap<double>((x, y) => x.CompareTo(y)); for (int i = 0; i < insertCount; i++) { tree = tree.Insert(rnd.NextDouble()); } } static void OrderedInsert(int insertCount) { Treap<double> tree = new Treap<double>((x, y) => x.CompareTo(y)); for(int i = 0; i < insertCount; i++) { tree = tree.Insert(i + rnd.NextDouble()); } } } } And here's a chart comparing random and ordered insertion times in milliseconds: Insertions Random Ordered RandomTime / OrderedTime 50 1.031665 0.261585 3.94 100 0.544345 1.377155 0.4 200 1.268320 0.734570 1.73 400 2.765555 1.639150 1.69 800 6.089700 3.558350 1.71 1000 7.855150 4.704190 1.67 2000 17.852000 12.554065 1.42 4000 40.157340 22.474445 1.79 8000 88.375430 48.364265 1.83 16000 197.524000 109.082200 1.81 32000 459.277050 238.154405 1.93 64000 1055.508875 512.020310 2.06 128000 2481.694230 1107.980425 2.24 I don't see anything in the code which makes ordered input asymptotically faster than unordered input, so I'm at a loss to explain the difference. Why is it so much faster to build a treap from ordered input than random input?

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  • Where should the partitioning column go in the primary key on SQL Server?

    - by Bialecki
    Using SQL Server 2005 and 2008. I've got a potentially very large table (potentially hundreds of millions of rows) consisting of the following columns: CREATE TABLE ( date SMALLDATETIME, id BIGINT, value FLOAT ) which is being partitioned on column date in daily partitions. The question then is should the primary key be on date, id or value, id? I can imagine that SQL Server is smart enough to know that it's already partitioning on date and therefore, if I'm always querying for whole chunks of days, then I can have it second in the primary key. Or I can imagine that SQL Server will need that column to be first in the primary key to get the benefit of partitioning. Can anyone lend some insight into which way the table should be keyed?

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  • What's holding up my PHP script?

    - by gAMBOOKa
    We've got a PHP crawler running on our web server. When the crawler is running, there are no cpu, memory or network bandwidth spikes. Everything is normal. But our website (also PHP), hosted on the same server, stops responding. Basically the crawler blocks any other php script from running. What could be the problem? EDIT: ** fsockopen is being used to download files to crawler! **

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  • How many layers are between my program and the hardware?

    - by sub
    I somehow have the feeling that modern systems, including runtime libraries, this exception handler and that built-in debugger build up more and more layers between my (C++) programs and the CPU/rest of the hardware. I'm thinking of something like this: 1 + 2 OS top layer Runtime library/helper/error handler a hell lot of DLL modules OS kernel layer Do you really want to run 1 + 2?-Windows popup (don't take this serious) OS kernel layer Hardware abstraction Hardware Go through at least 100 miles of circuits Eventually arrive at the CPU ADD 1, 2 Go all the way back to my program Nearly all technical things are simply wrong and in some random order, but you get my point right? How much longer/shorter is this chain when I run a C++ program that calculates 1 + 2 at runtime on Windows? How about when I do this in an interpreter? (Python|Ruby|PHP) Is this chain really as dramatic in reality? Does Windows really try "not to stand in the way"? e.g.: Direct connection my binary < hardware?

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  • Detecting Connection Speed / Bandwidth in .net/WCF

    - by Mystagogue
    I'm writing both client and server code using WCF, where I need to know the "perceived" bandwidth of traffic between the client and server. I could use ping statistics to gather this information separately, but I wonder if there is a way to configure the channel stack in WCF so that the same statistics can be gathered simultaneously while performing my web service invocations. This would be particularly useful in cases where ICMP is disabled (e.g. ping won't work). In short, while making my regular business-related web service calls (REST calls to be precise), is there a way to collect connection speed data implicitly? Certainly I could time the web service round trip, compared to the size of data used in the round-trip, to give me an idea of throughput - but I won't know how much of that perceived bandwidth was network related, or simply due to server-processing latency. I could perhaps solve that by having the server send back a time delta, representing server latency, so that the client can compute the actual network traffic time. If a more sophisticated approach is not available, that might be my answer...

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  • Grails application hogging too much memory

    - by RN
    Tomcat 5.5.x and 6.0.x Grails 1.6.x Java 1.6.x OS CentOS 5.x (64bit) VPS Server with memory as 384M export JAVA_OPTS='-Xms128M -Xmx512M -XX:MaxPermSize=1024m' I have created a blank Grails application i.e simply by giving the command grails create-app and then WARed it I am running Tomcat on a VPS Server When I simply start the Tomcat server, with no apps deployed, the free memory is about 236M and used memory is about 156M When I deploy my "blank" application, the memory consumption spikes to 360M and finally the Tomcat instance is killed as soon as it takes up all free memory As you have seen, my app is as light as it can be. Not sure why the memory consumption is as high it is. I am actually troubleshooting a real application, but have narrowed down to this scenario which is easier to share and explain.

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  • Web Application Translation, methods and tools

    - by CiscoIPPhone
    I've developed a web application. It needs to be translated to languages other than English in the future, and ideally the translators shouldn't need to know HTML/JS/C++ to provide the translation. The server side of the web application is written in C++ and the majority of the localised text is in the HTML files. My question is: What approaches are there to translating web applications? - Are there any existing tools that would enable a translator who doesn't understand HTML to translate a site? Should I write an application that extracts the localised text from a html file and can re-substitute translated text? Do you just provide the html file to your translators to be localised? I'm aware the question isn't strictly programming related but the solution may involve programming and it may require some software engineering.

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  • Very slow Eclipse 4.2, how to make it more responsive?

    - by Laurent
    I'm using Eclipse PDT on a rather large PHP project and the IDE is almost unusable. It takes nearly 30 seconds to open a file, and other actions, like selecting a folder in the file explorer, editing some text, etc. are equally slow. I followed various instructions to speed it up but nothing seems to work. This is my current eclipse.ini file. Any idea how I can improve it? -startup plugins/org.eclipse.equinox.launcher_1.3.0.v20120522-1813.jar --launcher.library plugins/org.eclipse.equinox.launcher.win32.win32.x86_1.1.200.v20120522-1813 -showsplash org.eclipse.platform --launcher.XXMaxPermSize 256m --launcher.defaultAction openFile -vmargs -server -Dosgi.requiredJavaVersion=1.7 -Xmn128m -Xms1024m -Xmx1024m -Xss2m -XX:PermSize=128m -XX:MaxPermSize=128m -XX:+UseParallelGC System: Eclipse 4.2.0, Windows 7, 4 GB RAM

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  • [C++]Advantage of using a static member function instead of an equivalent non-static member function

    - by jonathanasdf
    I was wondering whether there's any advantages to using a static member function when there is a non-static equivalent. Will it result in faster execution (because of not having to care about all of the member variables), or maybe less use of memory (because of not being included in all instances)? Basically, the function I'm looking at is an utility function to rotate an integer array representing pixel colours an arbitrary number of degrees around an arbitrary centre point. It is placed in my abstract Bullet base class, since only the bullets will be using it and I didn't want the overhead of calling it in some utility class. It's a bit too long and used in every single derived bullet class, making it probably not a good idea to inline. How would you suggest I define this function? As a static member function of Bullet, of a non-static member function of Bullet, or maybe not as a member of Bullet but defined outside of the class in Bullet.h? What are the advantages and disadvantages of each?

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  • Every 3rd Insert Is Slow On Ms Sql 2008

    - by Chris
    I have a function that writes 3 lines into a empty table like so: INSERT [dbo].[yaf_ForumAccess] ([GroupID], [ForumID], [AccessMaskID]) VALUES (1, 8, 1) INSERT [dbo].[yaf_ForumAccess] ([GroupID], [ForumID], [AccessMaskID]) VALUES (2, 8, 4) INSERT [dbo].[yaf_ForumAccess] ([GroupID], [ForumID], [AccessMaskID]) VALUES (3, 8, 3) For some reason only the third query takes a long time to execute - and with each insert it grows longer. Profiler Image I have tried disabling all constraints on the table - same result. I just can't figure out why the first two would run so fast - and the last one would take so long. Any help would be greatly appreciated. Here is the statistics for a query ran MSSMS: Query: ALTER TABLE [dbo].[yaf_ForumAccess] NOCHECK CONSTRAINT ALL INSERT [dbo].[yaf_ForumAccess] ([GroupID], [ForumID], [AccessMaskID]) VALUES (1, 9, 1) INSERT [dbo].[yaf_ForumAccess] ([GroupID], [ForumID], [AccessMaskID]) VALUES (2, 9, 4) INSERT [dbo].[yaf_ForumAccess] ([GroupID], [ForumID], [AccessMaskID]) VALUES (3, 9, 3) ALTER TABLE [dbo].[yaf_ForumAccess] CHECK CONSTRAINT ALL Stats: Stats

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  • Suggestions for a mashup application

    - by Raffo
    I have to write a mashup application for an university course and I have to use some APIs, but I need to choose by myself what to use and what the final application should do. Unfortunately I never made an application like this, so I'm not sure what to do... I don't want to code a stupid app which uses google maps' APIs since the web seems to be full of stuff like this. Have you got any suggestion for me? Is there any mashup web app you want that's still not there?? I can use JAVA, GWT (and google app engine of course) or python, but I also accept suggestions for other languages. Thank you in advance!

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  • Anyone using IronPython in a production application?

    - by Scott P
    I've been toying with the idea of adding IronPython for extending a scientific application I support. Is this a good or horrible idea? Are there any good examples of IronPython being used in a production application. I've seen Resolver, which is kind of cute. Are there any other apps out there? What I don't get is this. Is it any easier to use IronPython than to just use something like code DOM to create script like extensibility in your application? Anyone have some horror stories or tales of glorious success with IronPython / IronRuby?

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  • How to calculate real-time stats?

    - by Diego Jancic
    I have a site with millions of users (well, actually it doesn't have any yet, but let's imagine), and I want to calculate some stats like "log-ins in the past hour". The problem is similar to the one described here: http://highscalability.com/blog/2008/4/19/how-to-build-a-real-time-analytics-system.html The simplest approach would be to do a select like this: select count(distinct user_id) from logs where date>='20120601 1200' and date <='20120601 1300' (of course other conditions could apply for the stats, like log-ins per country) Of course this would be really slow, mainly if it has millions (or even thousands) of rows, and I want to query this every time a page is displayed. How would you summarize the data? What should go to the (mem)cache? EDIT: I'm looking for a way to de-normalize the data, or to keep the cache up-to-date. For example I could increment an in-memory variable every time someone logs in, but that would help to know the total amount of logins, not the "logins in the last hour". Hope it's more clear now.

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  • How to handle large dataset with JPA (or at least with Hibernate)?

    - by Roman
    I need to make my web-app work with really huge datasets. At the moment I get either OutOfMemoryException or output which is being generated 1-2 minutes. Let's put it simple and suppose that we have 2 tables in DB: Worker and WorkLog with about 1000 rows in the first one and 10 000 000 rows in the second one. Latter table has several fields including 'workerId' and 'hoursWorked' fields among others. What we need is: count total hours worked by each user; list of work periods for each user. The most straightforward approach (IMO) for each task in plain SQL is: 1) select Worker.name, sum(hoursWorked) from Worker, WorkLog where Worker.id = WorkLog.workerId group by Worker.name; //results of this query should be transformed to Multimap<Worker, Long> 2) select Worker.name, WorkLog.start, WorkLog.hoursWorked from Worker, WorkLog where Worker.id = WorkLog.workerId; //results of this query should be transformed to Multimap<Worker, Period> //if it was JDBC then it would be vitally //to set resultSet.setFetchSize (someSmallNumber), ~100 So, I have two questions: how to implement each of my approaches with JPA (or at least with Hibernate); how would you handle this problem (with JPA or Hibernate of course)?

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  • Question about Cost in Oracle Explain Plan

    - by Will
    When Oracle is estimating the 'Cost' for certain queries, does it actually look at the amount of data (rows) in a table? For example: If I'm doing a full table scan of employees for name='Bob', does it estimate the cost by counting the amount of existing rows, or is it always a set cost?

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  • SQL indexing on varchar

    - by alex
    I have a table whose columns are varchar(50) and a float - I need to (very quickly) look get the float associated with a given string. Even with indexing, this is rather slow. I know, however, that each string is associated with an integer, which I know at the time of lookup, so that each string maps to a unique integer, but each integer does not map to a unique string. One might think of it as a tree structure. Is there anything to be gained by adding this integer to the table, indexing on it, and using a query like SELECT floatval FROM mytable WHERE phrase=givenstring AND assoc=givenint? This is Postgres, and if you couldn't tell, I have very little experience with databases.

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  • How To Make Moving News Bar in Windows Forms Application without Timer

    - by Ehab Sutan
    I'm making a desktop application in C# which contains a moving News Bar labels. I'm using a timer to move these labels but the problem is that when i make the interval of this timer low (1-10 for example) the application takes very high percentage of CPU Usage, And when i make it higher(200 -500 ) the movement of the labels becomes intermittent or not smooth movement even that the user may not be able to read the news in Comfortable way. ((More Information)) it is Windows form application. the way i move the labels is as follows : the news items from RSS feeds are represented in a group of linklabels. All these linklabels are added to a flowlayout container. The timer moves the whole flowlayout container. I found this way according to my knowledge the best way to making the news bar. If you have better idea or solution please help

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