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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • MySQL query cache vs caching result-sets in the application layer

    - by GetFree
    I'm running a php/mysql-driven website with a lot of visits and I'm considering the possibility of caching result-sets in shared memory in order to reduce database load. However, right now MySQL's query cache is enabled and it seems to be doing a pretty good job since if I disable query caching, the use of CPU jumps to 100% immediately. Given that situation, I dont know if caching result-sets (or even the generated HTML code) locally in shared memory with PHP will result in any noticeable performace improvement. Does anyone out there have any experience on this matter? PS: Please avoid suggesting heavy-artillery solutions like memcached. Right now I'm looking for simple solutions that dont require too much time to implement, deploy and maintain.

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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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  • Threading cost - minimum execution time when threads would add speed

    - by Lukas
    I am working on a C# application that works with an array. It walks through it (meaning that at one time only a narrow part of the array is used). I am considering adding threads in it to make it perform faster (it runs on a dualcore computer). The problem is that I do not know if it would actually help, because threads cost something and this cost could easily be more than the parallel gain... So how do I determine if threading would help?

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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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  • What is faster with PictureBox? Many small redraws or complete redraw.

    - by kornelijepetak
    I have a PictureBox (WinMobile 6 WinForm) on which I draw some images. There is a background image that goes in the background and it does not change. However objects that are drawn on the picturebox are moving during the application so I need to refresh the background. Since items that are redrawn fill from 50% to 80% of the surface, the question is which of the two is faster: 1) Redraw only parts of the background image that have been changed (previous+next location of the moving object). 2) Redraw complete background and then draw all the objects in their current position. Now, the reason for asking is because I am not sure how much of processor power is needed for a single drawImage operation and what are the time consuming factors. I am aware if there is almost complete coverage of the background, it would be stupid to redraw portions of it, because by drawing portions I will have drawn the complete picture. But since sometimes only half of the image had changed (some objects remained in their old position), it may (perhaps) be benefitial to redraw only those regions. But I need your insight on this... Thanks.

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  • ASP.NET How expensive is it to call an Application Variable many times?

    - by Matias Nino
    The short of it is: Is it costly to check an Application Variable such as Application("WebAppName") more 10-20 times each time a page loads? Background: (feel free to critique) Some includes in my site contain many links and images which cannot use relative urls due to their inclusion in different paths. Hence these includes contain frequent instances of <img src="<%=Application("Webroot")%>images\image.gif"> Is it expensive to keep calling an Application variable like this? Should I just put the Application value in some local variable to use where needed? IMPORTANT NOTE: I need my webapp to run fine on a server whether it be in the root web ("/") or in a virtual subweb ("/app"). Thanks in advance for any wisdom shared.

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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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  • 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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  • 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 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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  • 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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  • Efficient data structure design

    - by Sway
    Hi there, I need to match a series of user inputed words against a large dictionary of words (to ensure the entered value exists). So if the user entered: "orange" it should match an entry "orange' in the dictionary. Now the catch is that the user can also enter a wildcard or series of wildcard characters like say "or__ge" which would also match "orange" The key requirements are: * this should be as fast as possible. * use the smallest amount of memory to achieve it. If the size of the word list was small I could use a string containing all the words and use regular expressions. however given that the word list could contain potentially hundreds of thousands of enteries I'm assuming this wouldn't work. So is some sort of 'tree' be the way to go for this...? Any thoughts or suggestions on this would be totally appreciated! Thanks in advance, Matt

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  • comparing two cursors in oracle instead of using MINUS

    - by Omnipresent
    The following query takes more than 3 minutes to run because tables contain massive amounts of data: SELECT RTRIM(LTRIM(A.HEAD)), A.EFFECTIVE_DATE, FROM TABLE_1 A WHERE A.TYPE_OF_ACTION='6' AND A.EFFECTIVE_DATE >= ADD_MONTHS(SYSDATE,-15) MINUS SELECT RTRIM(LTRIM(B.head)), B.EFFECTIVE_DATE, FROM TABLE_2 B In our system a query gets killed if it is running for more than 8 seconds. Is there a way to run the queries individually ..put them in cursors..compare and then get the results? that way each query will be ran individually rather than as one massive query which takes 3 minutes. How would two cursors be compared to mimic the MINUS?

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  • Hibernate design to speed up querying of large dataset

    - by paddydub
    I currently have the below tables representing a bus network mapped in hibernate, accessed from a Spring MVC based bus route planner I'm trying to make my route planner application perform faster, I load all the above tables into Lists to perform the route planner logic. I would appreciate if anyone has any ideas of how to speed my performace Or any suggestions of another method to approach this problem of handling a large set of data Coordinate Connections Table (INT,INT,INT, DOUBLE)( Containing 50,000 Coordinate Connections) ID, FROMCOORDID, TOCOORDID, DISTANCE 1 1 2 0.383657 2 1 17 0.173201 3 1 63 0.258781 4 1 64 0.013726 5 1 65 0.459829 6 1 95 0.458769 Coordinate Table (INT,DECIMAL, DECIMAL) (Containing 4700 Coordinates) ID , LAT, LNG 0 59.352669 -7.264341 1 59.352669 -7.264341 2 59.350012 -7.260653 3 59.337585 -7.189798 4 59.339221 -7.193582 5 59.341408 -7.205888 Bus Stop Table (INT, INT, INT)(Containing 15000 Stops) StopID RouteID COORDINATEID 1000100001 100 17 1000100002 100 18 1000100003 100 19 1000100004 100 20 1000100005 100 21 1000100006 100 22 1000100007 100 23 This is how long it takes to load all the data from each table: stop.findAll = 148ms, stops.size: 15670 Hibernate: select coordinate0_.COORDINATEID as COORDINA1_2_, coordinate0_.LAT as LAT2_, coordinate0_.LNG as LNG2_ from COORDINATES coordinate0_ coord.findAll = 51ms , coordinates.size: 4704 Hibernate: select coordconne0_.COORDCONNECTIONID as COORDCON1_3_, coordconne0_.DISTANCE as DISTANCE3_, coordconne0_.FROMCOORDID as FROMCOOR3_3_, coordconne0_.TOCOORDID as TOCOORDID3_ from COORDCONNECTIONS coordconne0_ coordinateConnectionDao.findAll = 238ms ; coordConnectioninates.size:48132 Hibernate Annotations @Entity @Table(name = "STOPS") public class Stop implements Serializable { @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "STOPID") private int stopID; @Column(name = "ROUTEID", nullable = false) private int routeID; @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "COORDINATEID", nullable = false) private Coordinate coordinate; } @Table(name = "COORDINATES") public class Coordinate { @Id @GeneratedValue @Column(name = "COORDINATEID") private int CoordinateID; @Column(name = "LAT") private double latitude; @Column(name = "LNG") private double longitude; } @Entity @Table(name = "COORDCONNECTIONS") public class CoordConnection { @Id @GeneratedValue @Column(name = "COORDCONNECTIONID") private int CoordinateID; @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "FROMCOORDID", nullable = false) private Coordinate fromCoordID; @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "TOCOORDID", nullable = false) private Coordinate toCoordID; @Column(name = "DISTANCE", nullable = false) private double distance; }

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